virtualization/linux-yocto: Backport virtio SCMI driver.

This patch series is a "RFC v2" implementation of a driver for
virtio SCMI device [1].

[1]: https://github.com/oasis-tcs/virtio-spec/blob/master/virtio-scmi.tex

Bug-AGL: SPEC-3865
Upstream-Status: Submitted [https://lore.kernel.org/linux-arm-kernel/20201105212116.411422-1-peter.hilber@opensynergy.com/]
Signed-off-by: Andriy Tryshnivskyy <andriy.tryshnivskyy@opensynergy.com>
Change-Id: I653cb44769232ae5434bd54169910fd0518f1db8

10 files changed, 1476 insertions, 0 deletions

diff --git a/meta-egvirt/recipes-kernel/linux/linux-yocto/virtio-scmi/0001-firmware-arm_scmi-smccc-mailbox-Make-shmem-based-tra.patch b/meta-egvirt/recipes-kernel/linux/linux-yocto/virtio-scmi/0001-firmware-arm_scmi-smccc-mailbox-Make-shmem-based-tra.patch
new file mode 100644
index 00000000..3d9d0fdb
--- /dev/null
+++ b/meta-egvirt/recipes-kernel/linux/linux-yocto/virtio-scmi/0001-firmware-arm_scmi-smccc-mailbox-Make-shmem-based-tra.patch
@@ -0,0 +1,119 @@
+From 36269e8f5fa1f33a793c472935affe3039c052bd Mon Sep 17 00:00:00 2001
+From: Igor Skalkin <igor.skalkin@opensynergy.com>
+Date: Thu, 5 Nov 2020 22:21:07 +0100
+Subject: [PATCH] firmware: arm_scmi, smccc, mailbox: Make shmem based
+ transports optional
+
+Upon adding the virtio transport in this patch series, SCMI will also
+work without shared memory based transports. Also, the mailbox transport
+may not be needed if the smc transport is used.
+
+- Compile shmem.c only if a shmem based transport is available.
+
+- Remove hard dependency of SCMI on mailbox.
+
+Co-developed-by: Peter Hilber <peter.hilber@opensynergy.com>
+Signed-off-by: Peter Hilber <peter.hilber@opensynergy.com>
+Signed-off-by: Igor Skalkin <igor.skalkin@opensynergy.com>
+Signed-off-by: Vasyl Vavrychuk <vasyl.vavrychuk@opensynergy.com>
+---
+ drivers/firmware/Kconfig           | 9 ++++++++-
+ drivers/firmware/arm_scmi/Makefile | 2 +-
+ drivers/firmware/arm_scmi/common.h | 2 ++
+ drivers/firmware/arm_scmi/driver.c | 2 ++
+ drivers/firmware/smccc/Kconfig     | 1 +
+ drivers/mailbox/Kconfig            | 1 +
+ 6 files changed, 15 insertions(+), 2 deletions(-)
+
+diff --git a/drivers/firmware/Kconfig b/drivers/firmware/Kconfig
+index 3315e3c21586..30a85d38d0c0 100644
+--- a/drivers/firmware/Kconfig
++++ b/drivers/firmware/Kconfig
+@@ -9,7 +9,7 @@ menu "Firmware Drivers"
+ config ARM_SCMI_PROTOCOL
+ 	tristate "ARM System Control and Management Interface (SCMI) Message Protocol"
+ 	depends on ARM || ARM64 || COMPILE_TEST
+-	depends on MAILBOX
++	depends on ARM_SCMI_HAVE_SHMEM
+ 	help
+ 	  ARM System Control and Management Interface (SCMI) protocol is a
+ 	  set of operating system-independent software interfaces that are
+@@ -27,6 +27,13 @@ config ARM_SCMI_PROTOCOL
+ 	  This protocol library provides interface for all the client drivers
+ 	  making use of the features offered by the SCMI.
+ 
++config ARM_SCMI_HAVE_SHMEM
++	bool
++	default n
++	help
++	  This declares whether a shared memory based transport for SCMI is
++	  available.
++
+ config ARM_SCMI_POWER_DOMAIN
+ 	tristate "SCMI power domain driver"
+ 	depends on ARM_SCMI_PROTOCOL || (COMPILE_TEST && OF)
+diff --git a/drivers/firmware/arm_scmi/Makefile b/drivers/firmware/arm_scmi/Makefile
+index bc0d54f8e861..3cc7fa40a464 100644
+--- a/drivers/firmware/arm_scmi/Makefile
++++ b/drivers/firmware/arm_scmi/Makefile
+@@ -1,7 +1,7 @@
+ # SPDX-License-Identifier: GPL-2.0-only
+ scmi-bus-y = bus.o
+ scmi-driver-y = driver.o notify.o
+-scmi-transport-y = shmem.o
++scmi-transport-$(CONFIG_ARM_SCMI_HAVE_SHMEM) = shmem.o
+ scmi-transport-$(CONFIG_MAILBOX) += mailbox.o
+ scmi-transport-$(CONFIG_HAVE_ARM_SMCCC_DISCOVERY) += smc.o
+ scmi-protocols-y = base.o clock.o perf.o power.o reset.o sensors.o system.o
+diff --git a/drivers/firmware/arm_scmi/common.h b/drivers/firmware/arm_scmi/common.h
+index 65063fa948d4..aed192238177 100644
+--- a/drivers/firmware/arm_scmi/common.h
++++ b/drivers/firmware/arm_scmi/common.h
+@@ -242,7 +242,9 @@ struct scmi_desc {
+ 	int max_msg_size;
+ };
+ 
++#ifdef CONFIG_MAILBOX
+ extern const struct scmi_desc scmi_mailbox_desc;
++#endif
+ #ifdef CONFIG_HAVE_ARM_SMCCC
+ extern const struct scmi_desc scmi_smc_desc;
+ #endif
+diff --git a/drivers/firmware/arm_scmi/driver.c b/drivers/firmware/arm_scmi/driver.c
+index 6b2ce3f28f7b..7efbf66f117b 100644
+--- a/drivers/firmware/arm_scmi/driver.c
++++ b/drivers/firmware/arm_scmi/driver.c
+@@ -918,7 +918,9 @@ ATTRIBUTE_GROUPS(versions);
+ 
+ /* Each compatible listed below must have descriptor associated with it */
+ static const struct of_device_id scmi_of_match[] = {
++#ifdef CONFIG_MAILBOX
+ 	{ .compatible = "arm,scmi", .data = &scmi_mailbox_desc },
++#endif
+ #ifdef CONFIG_HAVE_ARM_SMCCC_DISCOVERY
+ 	{ .compatible = "arm,scmi-smc", .data = &scmi_smc_desc},
+ #endif
+diff --git a/drivers/firmware/smccc/Kconfig b/drivers/firmware/smccc/Kconfig
+index 15e7466179a6..69c4d6cabf62 100644
+--- a/drivers/firmware/smccc/Kconfig
++++ b/drivers/firmware/smccc/Kconfig
+@@ -9,6 +9,7 @@ config HAVE_ARM_SMCCC_DISCOVERY
+ 	bool
+ 	depends on ARM_PSCI_FW
+ 	default y
++	select ARM_SCMI_HAVE_SHMEM
+ 	help
+ 	 SMCCC v1.0 lacked discoverability and hence PSCI v1.0 was updated
+ 	 to add SMCCC discovery mechanism though the PSCI firmware
+diff --git a/drivers/mailbox/Kconfig b/drivers/mailbox/Kconfig
+index 05b1009e2820..5ffe1ab0c869 100644
+--- a/drivers/mailbox/Kconfig
++++ b/drivers/mailbox/Kconfig
+@@ -1,6 +1,7 @@
+ # SPDX-License-Identifier: GPL-2.0-only
+ menuconfig MAILBOX
+ 	bool "Mailbox Hardware Support"
++	select ARM_SCMI_HAVE_SHMEM
+ 	help
+ 	  Mailbox is a framework to control hardware communication between
+ 	  on-chip processors through queued messages and interrupt driven
diff --git a/meta-egvirt/recipes-kernel/linux/linux-yocto/virtio-scmi/0002-firmware-arm_scmi-Document-that-max_msg-is-a-per-cha.patch b/meta-egvirt/recipes-kernel/linux/linux-yocto/virtio-scmi/0002-firmware-arm_scmi-Document-that-max_msg-is-a-per-cha.patch
new file mode 100644
index 00000000..7a21fedf
--- /dev/null
+++ b/meta-egvirt/recipes-kernel/linux/linux-yocto/virtio-scmi/0002-firmware-arm_scmi-Document-that-max_msg-is-a-per-cha.patch
@@ -0,0 +1,34 @@
+From 30de0a5e1fec42589469e5ec8951d15d364df63a Mon Sep 17 00:00:00 2001
+From: Igor Skalkin <igor.skalkin@opensynergy.com>
+Date: Thu, 5 Nov 2020 22:21:08 +0100
+Subject: [PATCH] firmware: arm_scmi: Document that max_msg is a per channel
+ type limit
+
+struct scmi_desc.max_msg specifies a limit for the pending messages.
+This limit is a per SCMI channel type (tx, rx) limit. State that
+explicitly in the inline documentation. The following patch will add an
+op to override the limit per channel type.
+
+Co-developed-by: Peter Hilber <peter.hilber@opensynergy.com>
+Signed-off-by: Peter Hilber <peter.hilber@opensynergy.com>
+Signed-off-by: Igor Skalkin <igor.skalkin@opensynergy.com>
+Signed-off-by: Vasyl Vavrychuk <vasyl.vavrychuk@opensynergy.com>
+---
+ drivers/firmware/arm_scmi/common.h | 4 ++--
+ 1 file changed, 2 insertions(+), 2 deletions(-)
+
+diff --git a/drivers/firmware/arm_scmi/common.h b/drivers/firmware/arm_scmi/common.h
+index aed192238177..38e6aabbe3dd 100644
+--- a/drivers/firmware/arm_scmi/common.h
++++ b/drivers/firmware/arm_scmi/common.h
+@@ -231,8 +231,8 @@ struct scmi_transport_ops {
+  *
+  * @ops: Pointer to the transport specific ops structure
+  * @max_rx_timeout_ms: Timeout for communication with SoC (in Milliseconds)
+- * @max_msg: Maximum number of messages that can be pending
+- *	simultaneously in the system
++ * @max_msg: Maximum number of messages for a channel type (tx or rx) that can
++ *	be pending simultaneously in the system
+  * @max_msg_size: Maximum size of data per message that can be handled.
+  */
+ struct scmi_desc {
diff --git a/meta-egvirt/recipes-kernel/linux/linux-yocto/virtio-scmi/0003-firmware-arm_scmi-Add-op-to-override-max-message.patch b/meta-egvirt/recipes-kernel/linux/linux-yocto/virtio-scmi/0003-firmware-arm_scmi-Add-op-to-override-max-message.patch
new file mode 100644
index 00000000..f58d6d88
--- /dev/null
+++ b/meta-egvirt/recipes-kernel/linux/linux-yocto/virtio-scmi/0003-firmware-arm_scmi-Add-op-to-override-max-message.patch
@@ -0,0 +1,165 @@
+From 9ffe778acc541cec68c954f84c6fcfef8a35bec2 Mon Sep 17 00:00:00 2001
+From: Igor Skalkin <igor.skalkin@opensynergy.com>
+Date: Thu, 5 Nov 2020 22:21:09 +0100
+Subject: [PATCH] firmware: arm_scmi: Add op to override max message #
+
+The number of messages that the upcoming scmi-virtio transport can
+support depends on the virtio device (SCMI platform) and can differ for
+each channel. (The scmi-virtio transport does only have one tx and at
+most 1 rx channel.)
+
+Add an optional transport op so that scmi-virtio can report the actual
+max message # for each channel type. Respect these new limits.
+
+Co-developed-by: Peter Hilber <peter.hilber@opensynergy.com>
+Signed-off-by: Peter Hilber <peter.hilber@opensynergy.com>
+Signed-off-by: Igor Skalkin <igor.skalkin@opensynergy.com>
+Signed-off-by: Vasyl Vavrychuk <vasyl.vavrychuk@opensynergy.com>
+---
+ drivers/firmware/arm_scmi/common.h |  8 ++++-
+ drivers/firmware/arm_scmi/driver.c | 49 ++++++++++++++++++++++--------
+ 2 files changed, 43 insertions(+), 14 deletions(-)
+
+diff --git a/drivers/firmware/arm_scmi/common.h b/drivers/firmware/arm_scmi/common.h
+index 38e6aabbe3dd..9a8359ecd220 100644
+--- a/drivers/firmware/arm_scmi/common.h
++++ b/drivers/firmware/arm_scmi/common.h
+@@ -203,6 +203,9 @@ struct scmi_chan_info {
+  * @chan_available: Callback to check if channel is available or not
+  * @chan_setup: Callback to allocate and setup a channel
+  * @chan_free: Callback to free a channel
++ * @get_max_msg: Optional callback to provide max_msg dynamically
++ * 	@max_msg: Maximum number of messages for the channel type (tx or rx)
++ * 		that can be pending simultaneously in the system
+  * @send_message: Callback to send a message
+  * @mark_txdone: Callback to mark tx as done
+  * @fetch_response: Callback to fetch response
+@@ -215,6 +218,8 @@ struct scmi_transport_ops {
+ 	int (*chan_setup)(struct scmi_chan_info *cinfo, struct device *dev,
+ 			  bool tx);
+ 	int (*chan_free)(int id, void *p, void *data);
++	int (*get_max_msg)(bool tx, struct scmi_chan_info *base_cinfo,
++			   int *max_msg);
+ 	int (*send_message)(struct scmi_chan_info *cinfo,
+ 			    struct scmi_xfer *xfer);
+ 	void (*mark_txdone)(struct scmi_chan_info *cinfo, int ret);
+@@ -232,7 +237,8 @@ struct scmi_transport_ops {
+  * @ops: Pointer to the transport specific ops structure
+  * @max_rx_timeout_ms: Timeout for communication with SoC (in Milliseconds)
+  * @max_msg: Maximum number of messages for a channel type (tx or rx) that can
+- *	be pending simultaneously in the system
++ *	be pending simultaneously in the system. May be overridden by the
++ *	get_max_msg op.
+  * @max_msg_size: Maximum size of data per message that can be handled.
+  */
+ struct scmi_desc {
+diff --git a/drivers/firmware/arm_scmi/driver.c b/drivers/firmware/arm_scmi/driver.c
+index 7efbf66f117b..5baa23789a49 100644
+--- a/drivers/firmware/arm_scmi/driver.c
++++ b/drivers/firmware/arm_scmi/driver.c
+@@ -61,11 +61,13 @@ static atomic_t transfer_last_id;
+  *	Index of this bitmap table is also used for message
+  *	sequence identifier.
+  * @xfer_lock: Protection for message allocation
++ * @max_msg: Maximum number of messages that can be pending
+  */
+ struct scmi_xfers_info {
+ 	struct scmi_xfer *xfer_block;
+ 	unsigned long *xfer_alloc_table;
+ 	spinlock_t xfer_lock;
++	int max_msg;
+ };
+ 
+ /**
+@@ -157,13 +159,11 @@ static struct scmi_xfer *scmi_xfer_get(const struct scmi_handle *handle,
+ 	u16 xfer_id;
+ 	struct scmi_xfer *xfer;
+ 	unsigned long flags, bit_pos;
+-	struct scmi_info *info = handle_to_scmi_info(handle);
+ 
+ 	/* Keep the locked section as small as possible */
+ 	spin_lock_irqsave(&minfo->xfer_lock, flags);
+-	bit_pos = find_first_zero_bit(minfo->xfer_alloc_table,
+-				      info->desc->max_msg);
+-	if (bit_pos == info->desc->max_msg) {
++	bit_pos = find_first_zero_bit(minfo->xfer_alloc_table, minfo->max_msg);
++	if (bit_pos == minfo->max_msg) {
+ 		spin_unlock_irqrestore(&minfo->xfer_lock, flags);
+ 		return ERR_PTR(-ENOMEM);
+ 	}
+@@ -602,32 +602,44 @@ int scmi_handle_put(const struct scmi_handle *handle)
+ }
+ 
+ static int __scmi_xfer_info_init(struct scmi_info *sinfo,
+-				 struct scmi_xfers_info *info)
++				 struct scmi_xfers_info *info,
++				 bool tx,
++				 struct scmi_chan_info *base_cinfo)
+ {
+ 	int i;
+ 	struct scmi_xfer *xfer;
+ 	struct device *dev = sinfo->dev;
+ 	const struct scmi_desc *desc = sinfo->desc;
+ 
++	info->max_msg = desc->max_msg;
++
++	if (desc->ops->get_max_msg) {
++		int ret =
++			desc->ops->get_max_msg(tx, base_cinfo, &info->max_msg);
++
++		if (ret)
++			return ret;
++	}
++
+ 	/* Pre-allocated messages, no more than what hdr.seq can support */
+-	if (WARN_ON(desc->max_msg >= MSG_TOKEN_MAX)) {
++	if (WARN_ON(info->max_msg >= MSG_TOKEN_MAX)) {
+ 		dev_err(dev, "Maximum message of %d exceeds supported %ld\n",
+-			desc->max_msg, MSG_TOKEN_MAX);
++			info->max_msg, MSG_TOKEN_MAX);
+ 		return -EINVAL;
+ 	}
+ 
+-	info->xfer_block = devm_kcalloc(dev, desc->max_msg,
++	info->xfer_block = devm_kcalloc(dev, info->max_msg,
+ 					sizeof(*info->xfer_block), GFP_KERNEL);
+ 	if (!info->xfer_block)
+ 		return -ENOMEM;
+ 
+-	info->xfer_alloc_table = devm_kcalloc(dev, BITS_TO_LONGS(desc->max_msg),
++	info->xfer_alloc_table = devm_kcalloc(dev, BITS_TO_LONGS(info->max_msg),
+ 					      sizeof(long), GFP_KERNEL);
+ 	if (!info->xfer_alloc_table)
+ 		return -ENOMEM;
+ 
+ 	/* Pre-initialize the buffer pointer to pre-allocated buffers */
+-	for (i = 0, xfer = info->xfer_block; i < desc->max_msg; i++, xfer++) {
++	for (i = 0, xfer = info->xfer_block; i < info->max_msg; i++, xfer++) {
+ 		xfer->rx.buf = devm_kcalloc(dev, sizeof(u8), desc->max_msg_size,
+ 					    GFP_KERNEL);
+ 		if (!xfer->rx.buf)
+@@ -644,10 +656,21 @@ static int __scmi_xfer_info_init(struct scmi_info *sinfo,
+ 
+ static int scmi_xfer_info_init(struct scmi_info *sinfo)
+ {
+-	int ret = __scmi_xfer_info_init(sinfo, &sinfo->tx_minfo);
++	int ret;
++	struct scmi_chan_info *base_tx_cinfo;
++	struct scmi_chan_info *base_rx_cinfo;
++
++	base_tx_cinfo = idr_find(&sinfo->tx_idr, SCMI_PROTOCOL_BASE);
++	if (unlikely(!base_tx_cinfo))
++		return -EINVAL;
++
++	ret = __scmi_xfer_info_init(sinfo, &sinfo->tx_minfo, true,
++				    base_tx_cinfo);
+ 
+-	if (!ret && idr_find(&sinfo->rx_idr, SCMI_PROTOCOL_BASE))
+-		ret = __scmi_xfer_info_init(sinfo, &sinfo->rx_minfo);
++	base_rx_cinfo = idr_find(&sinfo->rx_idr, SCMI_PROTOCOL_BASE);
++	if (!ret && base_rx_cinfo)
++		ret = __scmi_xfer_info_init(sinfo, &sinfo->rx_minfo, false,
++					    base_rx_cinfo);
+ 
+ 	return ret;
+ }
diff --git a/meta-egvirt/recipes-kernel/linux/linux-yocto/virtio-scmi/0004-firmware-arm_scmi-Add-per-message-transport-data.patch b/meta-egvirt/recipes-kernel/linux/linux-yocto/virtio-scmi/0004-firmware-arm_scmi-Add-per-message-transport-data.patch
new file mode 100644
index 00000000..644b015d
--- /dev/null
+++ b/meta-egvirt/recipes-kernel/linux/linux-yocto/virtio-scmi/0004-firmware-arm_scmi-Add-per-message-transport-data.patch
@@ -0,0 +1,42 @@
+From 0771d1d96e6439c00497a521f8d2c9803f7e07e2 Mon Sep 17 00:00:00 2001
+From: Igor Skalkin <igor.skalkin@opensynergy.com>
+Date: Thu, 5 Nov 2020 22:21:10 +0100
+Subject: [PATCH] firmware: arm_scmi: Add per message transport data
+
+The virtio transport in this patch series can be simplified by using the
+scmi_xfer tx/rx buffers for data exchange with the virtio device, and
+for saving the message state. But the virtio transport requires
+prepending a transport-specific header. Also, for data exchange using
+virtqueues, the tx and rx buffers should not overlap.
+
+The first step to solve the aforementioned issues is to add a
+transport-specific data pointer to scmi_xfer.
+
+Co-developed-by: Peter Hilber <peter.hilber@opensynergy.com>
+Signed-off-by: Peter Hilber <peter.hilber@opensynergy.com>
+Signed-off-by: Igor Skalkin <igor.skalkin@opensynergy.com>
+Signed-off-by: Vasyl Vavrychuk <vasyl.vavrychuk@opensynergy.com>
+---
+ drivers/firmware/arm_scmi/common.h | 2 ++
+ 1 file changed, 2 insertions(+)
+
+diff --git a/drivers/firmware/arm_scmi/common.h b/drivers/firmware/arm_scmi/common.h
+index 9a8359ecd220..c998ec29018e 100644
+--- a/drivers/firmware/arm_scmi/common.h
++++ b/drivers/firmware/arm_scmi/common.h
+@@ -131,6 +131,7 @@ struct scmi_msg {
+  *	buffer for the rx path as we use for the tx path.
+  * @done: command message transmit completion event
+  * @async_done: pointer to delayed response message received event completion
++ * @extra_data: Transport-specific private data pointer
+  */
+ struct scmi_xfer {
+ 	int transfer_id;
+@@ -139,6 +140,7 @@ struct scmi_xfer {
+ 	struct scmi_msg rx;
+ 	struct completion done;
+ 	struct completion *async_done;
++	void *extra_data;
+ };
+ 
+ void scmi_xfer_put(const struct scmi_handle *h, struct scmi_xfer *xfer);
diff --git a/meta-egvirt/recipes-kernel/linux/linux-yocto/virtio-scmi/0005-firmware-arm_scmi-Add-xfer_init_buffers-transport-op.patch b/meta-egvirt/recipes-kernel/linux/linux-yocto/virtio-scmi/0005-firmware-arm_scmi-Add-xfer_init_buffers-transport-op.patch
new file mode 100644
index 00000000..e62e5c50
--- /dev/null
+++ b/meta-egvirt/recipes-kernel/linux/linux-yocto/virtio-scmi/0005-firmware-arm_scmi-Add-xfer_init_buffers-transport-op.patch
@@ -0,0 +1,79 @@
+From fddb9bcd706ed3bb262f4f37707616dd06c7a4cc Mon Sep 17 00:00:00 2001
+From: Igor Skalkin <igor.skalkin@opensynergy.com>
+Date: Thu, 5 Nov 2020 22:21:11 +0100
+Subject: [PATCH] firmware: arm_scmi: Add xfer_init_buffers transport op
+
+The virtio transport in this patch series can be simplified by using the
+scmi_xfer tx/rx buffers for data exchange with the virtio device, and
+for saving the message state. But the virtio transport requires
+prepending a transport-specific header. Also, for data exchange using
+virtqueues, the tx and rx buffers should not overlap.
+
+After the previous patch, this is the second and final step to enable
+the virtio transport to use the scmi_xfer buffers for data exchange.
+
+Add an optional op through which the transport can allocate the tx/rx
+buffers along with room for the prepended transport-specific headers.
+
+Co-developed-by: Peter Hilber <peter.hilber@opensynergy.com>
+Signed-off-by: Peter Hilber <peter.hilber@opensynergy.com>
+Signed-off-by: Igor Skalkin <igor.skalkin@opensynergy.com>
+Signed-off-by: Vasyl Vavrychuk <vasyl.vavrychuk@opensynergy.com>
+---
+ drivers/firmware/arm_scmi/common.h |  3 +++
+ drivers/firmware/arm_scmi/driver.c | 21 +++++++++++++++------
+ 2 files changed, 18 insertions(+), 6 deletions(-)
+
+diff --git a/drivers/firmware/arm_scmi/common.h b/drivers/firmware/arm_scmi/common.h
+index c998ec29018e..ae5db602e45d 100644
+--- a/drivers/firmware/arm_scmi/common.h
++++ b/drivers/firmware/arm_scmi/common.h
+@@ -208,6 +208,7 @@ struct scmi_chan_info {
+  * @get_max_msg: Optional callback to provide max_msg dynamically
+  * 	@max_msg: Maximum number of messages for the channel type (tx or rx)
+  * 		that can be pending simultaneously in the system
++ * @xfer_init_buffers: Callback to initialize buffers for scmi_xfer
+  * @send_message: Callback to send a message
+  * @mark_txdone: Callback to mark tx as done
+  * @fetch_response: Callback to fetch response
+@@ -222,6 +223,8 @@ struct scmi_transport_ops {
+ 	int (*chan_free)(int id, void *p, void *data);
+ 	int (*get_max_msg)(bool tx, struct scmi_chan_info *base_cinfo,
+ 			   int *max_msg);
++	int (*xfer_init_buffers)(struct scmi_chan_info *cinfo,
++				 struct scmi_xfer *xfer, int max_msg_size);
+ 	int (*send_message)(struct scmi_chan_info *cinfo,
+ 			    struct scmi_xfer *xfer);
+ 	void (*mark_txdone)(struct scmi_chan_info *cinfo, int ret);
+diff --git a/drivers/firmware/arm_scmi/driver.c b/drivers/firmware/arm_scmi/driver.c
+index 5baa23789a49..27dd43dcff5b 100644
+--- a/drivers/firmware/arm_scmi/driver.c
++++ b/drivers/firmware/arm_scmi/driver.c
+@@ -640,12 +640,21 @@ static int __scmi_xfer_info_init(struct scmi_info *sinfo,
+ 
+ 	/* Pre-initialize the buffer pointer to pre-allocated buffers */
+ 	for (i = 0, xfer = info->xfer_block; i < info->max_msg; i++, xfer++) {
+-		xfer->rx.buf = devm_kcalloc(dev, sizeof(u8), desc->max_msg_size,
+-					    GFP_KERNEL);
+-		if (!xfer->rx.buf)
+-			return -ENOMEM;
+-
+-		xfer->tx.buf = xfer->rx.buf;
++		if (desc->ops->xfer_init_buffers) {
++			int ret = desc->ops->xfer_init_buffers(
++				base_cinfo, xfer, desc->max_msg_size);
++
++			if (ret)
++				return ret;
++		} else {
++			xfer->rx.buf = devm_kcalloc(dev, sizeof(u8),
++						    desc->max_msg_size,
++						    GFP_KERNEL);
++			if (!xfer->rx.buf)
++				return -ENOMEM;
++
++			xfer->tx.buf = xfer->rx.buf;
++		}
+ 		init_completion(&xfer->done);
+ 	}
+ 
diff --git a/meta-egvirt/recipes-kernel/linux/linux-yocto/virtio-scmi/0006-firmware-arm_scmi-Add-optional-link_supplier-transpo.patch b/meta-egvirt/recipes-kernel/linux/linux-yocto/virtio-scmi/0006-firmware-arm_scmi-Add-optional-link_supplier-transpo.patch
new file mode 100644
index 00000000..0f5180fa
--- /dev/null
+++ b/meta-egvirt/recipes-kernel/linux/linux-yocto/virtio-scmi/0006-firmware-arm_scmi-Add-optional-link_supplier-transpo.patch
@@ -0,0 +1,54 @@
+From f0d7ff1f10ab846bf32bae3b7d32bf95653954fa Mon Sep 17 00:00:00 2001
+From: Peter Hilber <peter.hilber@opensynergy.com>
+Date: Thu, 5 Nov 2020 22:21:12 +0100
+Subject: [PATCH] firmware: arm_scmi: Add optional link_supplier() transport op
+
+For the scmi-virtio transport, it might not be possible to refer to the
+proper virtio device at device tree build time. Therefore, add an op
+which will allow scmi-virtio to dynamically link to the proper virtio
+device during probe.
+
+Signed-off-by: Peter Hilber <peter.hilber@opensynergy.com>
+Signed-off-by: Vasyl Vavrychuk <vasyl.vavrychuk@opensynergy.com>
+---
+ drivers/firmware/arm_scmi/common.h | 2 ++
+ drivers/firmware/arm_scmi/driver.c | 6 ++++++
+ 2 files changed, 8 insertions(+)
+
+diff --git a/drivers/firmware/arm_scmi/common.h b/drivers/firmware/arm_scmi/common.h
+index ae5db602e45d..2f55ac71555a 100644
+--- a/drivers/firmware/arm_scmi/common.h
++++ b/drivers/firmware/arm_scmi/common.h
+@@ -202,6 +202,7 @@ struct scmi_chan_info {
+ /**
+  * struct scmi_transport_ops - Structure representing a SCMI transport ops
+  *
++ * @link_supplier: Optional callback to add link to a supplier device
+  * @chan_available: Callback to check if channel is available or not
+  * @chan_setup: Callback to allocate and setup a channel
+  * @chan_free: Callback to free a channel
+@@ -217,6 +218,7 @@ struct scmi_chan_info {
+  * @poll_done: Callback to poll transfer status
+  */
+ struct scmi_transport_ops {
++	int (*link_supplier)(struct device *dev);
+ 	bool (*chan_available)(struct device *dev, int idx);
+ 	int (*chan_setup)(struct scmi_chan_info *cinfo, struct device *dev,
+ 			  bool tx);
+diff --git a/drivers/firmware/arm_scmi/driver.c b/drivers/firmware/arm_scmi/driver.c
+index 27dd43dcff5b..0b70f9ef9477 100644
+--- a/drivers/firmware/arm_scmi/driver.c
++++ b/drivers/firmware/arm_scmi/driver.c
+@@ -826,6 +826,12 @@ static int scmi_probe(struct platform_device *pdev)
+ 	handle->dev = info->dev;
+ 	handle->version = &info->version;
+ 
++	if (desc->ops->link_supplier) {
++		ret = desc->ops->link_supplier(dev);
++		if (ret)
++			return ret;
++	}
++
+ 	ret = scmi_txrx_setup(info, dev, SCMI_PROTOCOL_BASE);
+ 	if (ret)
+ 		return ret;
diff --git a/meta-egvirt/recipes-kernel/linux/linux-yocto/virtio-scmi/0007-firmware-arm_scmi-Add-per-device-transport-private-i.patch b/meta-egvirt/recipes-kernel/linux/linux-yocto/virtio-scmi/0007-firmware-arm_scmi-Add-per-device-transport-private-i.patch
new file mode 100644
index 00000000..1c82530f
--- /dev/null
+++ b/meta-egvirt/recipes-kernel/linux/linux-yocto/virtio-scmi/0007-firmware-arm_scmi-Add-per-device-transport-private-i.patch
@@ -0,0 +1,92 @@
+From 9d5366d4765fb60cafa31c2b46cd80d284c847bb Mon Sep 17 00:00:00 2001
+From: Peter Hilber <peter.hilber@opensynergy.com>
+Date: Thu, 5 Nov 2020 22:21:13 +0100
+Subject: [PATCH] firmware: arm_scmi: Add per-device transport private info
+
+The scmi-virtio transport will link a supplier device to the arm-scmi
+device in the link_supplier() op. The transport should then save a
+pointer to the linked device.
+
+To enable this, add a transport private info to the scmi_info. (The
+scmi_info is already reachable through the arm-scmi device driver_data.)
+
+Signed-off-by: Peter Hilber <peter.hilber@opensynergy.com>
+Signed-off-by: Vasyl Vavrychuk <vasyl.vavrychuk@opensynergy.com>
+---
+ drivers/firmware/arm_scmi/common.h |  2 ++
+ drivers/firmware/arm_scmi/driver.c | 35 ++++++++++++++++++++++++++++++
+ 2 files changed, 37 insertions(+)
+
+diff --git a/drivers/firmware/arm_scmi/common.h b/drivers/firmware/arm_scmi/common.h
+index 2f55ac71555a..ec9fd7fce3c7 100644
+--- a/drivers/firmware/arm_scmi/common.h
++++ b/drivers/firmware/arm_scmi/common.h
+@@ -262,6 +262,8 @@ extern const struct scmi_desc scmi_mailbox_desc;
+ extern const struct scmi_desc scmi_smc_desc;
+ #endif
+ 
++int scmi_set_transport_info(struct device *dev, void *transport_info);
++void *scmi_get_transport_info(struct device *dev);
+ void scmi_rx_callback(struct scmi_chan_info *cinfo, u32 msg_hdr);
+ void scmi_free_channel(struct scmi_chan_info *cinfo, struct idr *idr, int id);
+ 
+diff --git a/drivers/firmware/arm_scmi/driver.c b/drivers/firmware/arm_scmi/driver.c
+index 0b70f9ef9477..93ce17bb4079 100644
+--- a/drivers/firmware/arm_scmi/driver.c
++++ b/drivers/firmware/arm_scmi/driver.c
+@@ -84,6 +84,7 @@ struct scmi_xfers_info {
+  * @rx_idr: IDR object to map protocol id to Rx channel info pointer
+  * @protocols_imp: List of protocols implemented, currently maximum of
+  *	MAX_PROTOCOLS_IMP elements allocated by the base protocol
++ * @transport_info: Transport private info
+  * @node: List head
+  * @users: Number of users of this instance
+  */
+@@ -97,6 +98,7 @@ struct scmi_info {
+ 	struct idr tx_idr;
+ 	struct idr rx_idr;
+ 	u8 *protocols_imp;
++	void *transport_info;
+ 	struct list_head node;
+ 	int users;
+ };
+@@ -315,6 +317,39 @@ void scmi_rx_callback(struct scmi_chan_info *cinfo, u32 msg_hdr)
+ 	}
+ }
+ 
++/**
++ * scmi_set_transport_info() - Set transport private info
++ *
++ * @dev: SCMI instance device
++ * @transport_info: transport private info
++ *
++ * Return: 0 on success, otherwise error.
++ */
++int scmi_set_transport_info(struct device *dev, void *transport_info)
++{
++	struct scmi_info *info = dev_get_drvdata(dev);
++
++	if (!info)
++		return -EBADR;
++
++	info->transport_info = transport_info;
++	return 0;
++}
++
++/**
++ * scmi_get_transport_info() - Get transport private info
++ *
++ * @dev: SCMI instance device
++ *
++ * Return: transport private info on success, otherwise NULL.
++ */
++void *scmi_get_transport_info(struct device *dev)
++{
++	struct scmi_info *info = dev_get_drvdata(dev);
++
++	return info ? info->transport_info : NULL;
++}
++
+ /**
+  * scmi_xfer_put() - Release a transmit message
+  *
diff --git a/meta-egvirt/recipes-kernel/linux/linux-yocto/virtio-scmi/0008-firmware-arm_scmi-Add-is_scmi_protocol_device.patch b/meta-egvirt/recipes-kernel/linux/linux-yocto/virtio-scmi/0008-firmware-arm_scmi-Add-is_scmi_protocol_device.patch
new file mode 100644
index 00000000..92aad65e
--- /dev/null
+++ b/meta-egvirt/recipes-kernel/linux/linux-yocto/virtio-scmi/0008-firmware-arm_scmi-Add-is_scmi_protocol_device.patch
@@ -0,0 +1,46 @@
+From c4b299105e74f7863b2aa63bd838e7762761629c Mon Sep 17 00:00:00 2001
+From: Peter Hilber <peter.hilber@opensynergy.com>
+Date: Thu, 5 Nov 2020 22:21:14 +0100
+Subject: [PATCH] firmware: arm_scmi: Add is_scmi_protocol_device()
+
+The scmi-virtio transport driver will need to distinguish SCMI protocol
+devices from the SCMI instance device in the chan_setup() and
+chan_free() ops. Add this internal helper to be able to distinguish the
+two.
+
+Signed-off-by: Peter Hilber <peter.hilber@opensynergy.com>
+Signed-off-by: Vasyl Vavrychuk <vasyl.vavrychuk@opensynergy.com>
+---
+ drivers/firmware/arm_scmi/bus.c    | 5 +++++
+ drivers/firmware/arm_scmi/common.h | 2 ++
+ 2 files changed, 7 insertions(+)
+
+diff --git a/drivers/firmware/arm_scmi/bus.c b/drivers/firmware/arm_scmi/bus.c
+index 1377ec76a45d..4f19faafb2c5 100644
+--- a/drivers/firmware/arm_scmi/bus.c
++++ b/drivers/firmware/arm_scmi/bus.c
+@@ -108,6 +108,11 @@ static struct bus_type scmi_bus_type = {
+ 	.remove = scmi_dev_remove,
+ };
+ 
++bool is_scmi_protocol_device(struct device *dev)
++{
++	return dev->bus == &scmi_bus_type;
++}
++
+ int scmi_driver_register(struct scmi_driver *driver, struct module *owner,
+ 			 const char *mod_name)
+ {
+diff --git a/drivers/firmware/arm_scmi/common.h b/drivers/firmware/arm_scmi/common.h
+index ec9fd7fce3c7..13c9ac176b23 100644
+--- a/drivers/firmware/arm_scmi/common.h
++++ b/drivers/firmware/arm_scmi/common.h
+@@ -158,6 +158,8 @@ int scmi_version_get(const struct scmi_handle *h, u8 protocol, u32 *version);
+ void scmi_setup_protocol_implemented(const struct scmi_handle *handle,
+ 				     u8 *prot_imp);
+ 
++bool is_scmi_protocol_device(struct device *dev);
++
+ int scmi_base_protocol_init(struct scmi_handle *h);
+ 
+ int __init scmi_bus_init(void);
diff --git a/meta-egvirt/recipes-kernel/linux/linux-yocto/virtio-scmi/0009-dt-bindings-arm-Add-virtio-transport-for-SCMI.patch b/meta-egvirt/recipes-kernel/linux/linux-yocto/virtio-scmi/0009-dt-bindings-arm-Add-virtio-transport-for-SCMI.patch
new file mode 100644
index 00000000..beb2d99f
--- /dev/null
+++ b/meta-egvirt/recipes-kernel/linux/linux-yocto/virtio-scmi/0009-dt-bindings-arm-Add-virtio-transport-for-SCMI.patch
@@ -0,0 +1,89 @@
+From 592064dd36739ad5f3d885b9880ee1bc2d66e2df Mon Sep 17 00:00:00 2001
+From: Igor Skalkin <igor.skalkin@opensynergy.com>
+Date: Thu, 5 Nov 2020 22:21:15 +0100
+Subject: [PATCH] dt-bindings: arm: Add virtio transport for SCMI
+
+Document the properties for arm,scmi-virtio compatible nodes. The
+backing virtio SCMI device is described in patch [1].
+
+[1] https://lists.oasis-open.org/archives/virtio-comment/202005/msg00096.html
+
+Co-developed-by: Peter Hilber <peter.hilber@opensynergy.com>
+Signed-off-by: Peter Hilber <peter.hilber@opensynergy.com>
+Signed-off-by: Igor Skalkin <igor.skalkin@opensynergy.com>
+Signed-off-by: Vasyl Vavrychuk <vasyl.vavrychuk@opensynergy.com>
+---
+ .../devicetree/bindings/arm/arm,scmi.txt      | 35 +++++++++++++++++--
+ 1 file changed, 33 insertions(+), 2 deletions(-)
+
+diff --git a/Documentation/devicetree/bindings/arm/arm,scmi.txt b/Documentation/devicetree/bindings/arm/arm,scmi.txt
+index 55deb68230eb..6ded49d82773 100644
+--- a/Documentation/devicetree/bindings/arm/arm,scmi.txt
++++ b/Documentation/devicetree/bindings/arm/arm,scmi.txt
+@@ -13,6 +13,9 @@ the device tree.
+ Required properties:
+ 
+ The scmi node with the following properties shall be under the /firmware/ node.
++Some properties are specific to a transport type.
++
++shmem-based transports (mailbox, smc/hvc):
+ 
+ - compatible : shall be "arm,scmi" or "arm,scmi-smc" for smc/hvc transports
+ - mboxes: List of phandle and mailbox channel specifiers. It should contain
+@@ -21,6 +24,15 @@ The scmi node with the following properties shall be under the /firmware/ node.
+ 	  supported.
+ - shmem : List of phandle pointing to the shared memory(SHM) area as per
+ 	  generic mailbox client binding.
++
++Virtio transport:
++
++- compatible : shall be "arm,scmi-virtio".
++
++The virtio transport only supports a single device.
++
++Additional required properties:
++
+ - #address-cells : should be '1' if the device has sub-nodes, maps to
+ 	  protocol identifier for a given sub-node.
+ - #size-cells : should be '0' as 'reg' property doesn't have any size
+@@ -42,7 +54,8 @@ Each protocol supported shall have a sub-node with corresponding compatible
+ as described in the following sections. If the platform supports dedicated
+ communication channel for a particular protocol, the 3 properties namely:
+ mboxes, mbox-names and shmem shall be present in the sub-node corresponding
+-to that protocol.
++to that protocol. The virtio transport does not support dedicated communication
++channels.
+ 
+ Clock/Performance bindings for the clocks/OPPs based on SCMI Message Protocol
+ ------------------------------------------------------------
+@@ -106,7 +119,8 @@ Required sub-node properties:
+ [4] Documentation/devicetree/bindings/sram/sram.yaml
+ [5] Documentation/devicetree/bindings/reset/reset.txt
+ 
+-Example:
++Example (mailbox transport):
++----------------------------
+ 
+ sram@50000000 {
+ 	compatible = "mmio-sram";
+@@ -195,3 +209,20 @@ thermal-zones {
+ 		...
+ 	};
+ };
++
++Example (virtio transport):
++---------------------------
++
++virtio_mmio@4b001000 {
++	compatible = "virtio,mmio";
++	...
++};
++
++firmware {
++	...
++	scmi {
++		compatible = "arm,scmi-virtio";
++		...
++
++The rest is similar to the mailbox transport example, when omitting the
++mailbox/shmem-specific properties.
diff --git a/meta-egvirt/recipes-kernel/linux/linux-yocto/virtio-scmi/0010-firmware-arm_scmi-Add-virtio-transport.patch b/meta-egvirt/recipes-kernel/linux/linux-yocto/virtio-scmi/0010-firmware-arm_scmi-Add-virtio-transport.patch
new file mode 100644
index 00000000..35ea04f8
--- /dev/null
+++ b/meta-egvirt/recipes-kernel/linux/linux-yocto/virtio-scmi/0010-firmware-arm_scmi-Add-virtio-transport.patch
@@ -0,0 +1,756 @@
+From 7b9f3fe0766d6d36ca7465e54754df51ca175079 Mon Sep 17 00:00:00 2001
+From: Igor Skalkin <igor.skalkin@opensynergy.com>
+Date: Thu, 5 Nov 2020 22:21:16 +0100
+Subject: [PATCH] firmware: arm_scmi: Add virtio transport
+
+This transport enables accessing an SCMI platform as a virtio device.
+
+Implement an SCMI virtio driver according to the virtio SCMI device spec
+patch v5 [1]. Virtio device id 32 has been reserved for the SCMI device
+[2].
+
+The virtio transport has one tx channel (virtio cmdq, A2P channel) and
+at most one rx channel (virtio eventq, P2A channel).
+
+The following feature bit defined in [1] is not implemented:
+VIRTIO_SCMI_F_SHARED_MEMORY.
+
+After the preparatory patches, implement the virtio transport as
+paraphrased:
+
+Only support a single arm-scmi device (which is consistent with the SCMI
+spec). Call scmi-virtio init from arm-scmi module init. During the
+arm-scmi probing, link to the first probed scmi-virtio device. Defer
+arm-scmi probing if no scmi-virtio device is bound yet.
+
+Use the scmi_xfer tx/rx buffers for data exchange with the virtio device
+in order to avoid redundant maintenance of additional buffers. Allocate
+the buffers in the SCMI transport, and prepend room for a small header
+used by the virtio transport to the tx/rx buffers.
+
+For simplicity, restrict the number of messages which can be pending
+simultaneously according to the virtqueue capacity. (The virtqueue sizes
+are negotiated with the virtio device.)
+
+As soon as rx channel message buffers are allocated or have been read
+out by the arm-scmi driver, feed them to the virtio device.
+
+Since some virtio devices may not have the short response time exhibited
+by SCMI platforms using other transports, set a generous response
+timeout.
+
+Limitations:
+
+Do not adjust the other SCMI timeouts for delayed response and polling
+for now, since these timeouts are only relevant in special cases which
+are not yet deemed relevant for this transport.
+
+To do (as discussed in the cover letter):
+
+- Avoid re-use of buffers still being used by the virtio device on
+  timeouts.
+
+- Avoid race conditions on receiving messages during/after channel free
+  on driver probe failure or remove.
+
+[1] https://lists.oasis-open.org/archives/virtio-comment/202005/msg00096.html
+[2] https://www.oasis-open.org/committees/ballot.php?id=3496
+
+Co-developed-by: Peter Hilber <peter.hilber@opensynergy.com>
+Signed-off-by: Peter Hilber <peter.hilber@opensynergy.com>
+Signed-off-by: Igor Skalkin <igor.skalkin@opensynergy.com>
+Signed-off-by: Vasyl Vavrychuk <vasyl.vavrychuk@opensynergy.com>
+---
+ MAINTAINERS                        |   1 +
+ drivers/firmware/Kconfig           |  12 +-
+ drivers/firmware/arm_scmi/Makefile |   1 +
+ drivers/firmware/arm_scmi/common.h |  14 +
+ drivers/firmware/arm_scmi/driver.c |  11 +
+ drivers/firmware/arm_scmi/virtio.c | 493 +++++++++++++++++++++++++++++
+ include/uapi/linux/virtio_ids.h    |   1 +
+ include/uapi/linux/virtio_scmi.h   |  41 +++
+ 8 files changed, 573 insertions(+), 1 deletion(-)
+ create mode 100644 drivers/firmware/arm_scmi/virtio.c
+ create mode 100644 include/uapi/linux/virtio_scmi.h
+
+diff --git a/MAINTAINERS b/MAINTAINERS
+index 49772b741967..d223a5c3f465 100644
+--- a/MAINTAINERS
++++ b/MAINTAINERS
+@@ -16973,6 +16973,7 @@ F:	drivers/firmware/arm_scpi.c
+ F:	drivers/reset/reset-scmi.c
+ F:	include/linux/sc[mp]i_protocol.h
+ F:	include/trace/events/scmi.h
++F:	include/uapi/linux/virtio_scmi.h
+ 
+ SYSTEM RESET/SHUTDOWN DRIVERS
+ M:	Sebastian Reichel <sre@kernel.org>
+diff --git a/drivers/firmware/Kconfig b/drivers/firmware/Kconfig
+index 30a85d38d0c0..82e97904bcae 100644
+--- a/drivers/firmware/Kconfig
++++ b/drivers/firmware/Kconfig
+@@ -9,7 +9,7 @@ menu "Firmware Drivers"
+ config ARM_SCMI_PROTOCOL
+ 	tristate "ARM System Control and Management Interface (SCMI) Message Protocol"
+ 	depends on ARM || ARM64 || COMPILE_TEST
+-	depends on ARM_SCMI_HAVE_SHMEM
++	depends on ARM_SCMI_HAVE_SHMEM || VIRTIO_SCMI
+ 	help
+ 	  ARM System Control and Management Interface (SCMI) protocol is a
+ 	  set of operating system-independent software interfaces that are
+@@ -34,6 +34,16 @@ config ARM_SCMI_HAVE_SHMEM
+ 	  This declares whether a shared memory based transport for SCMI is
+ 	  available.
+ 
++config VIRTIO_SCMI
++	bool "Virtio transport for SCMI"
++	default n
++	depends on VIRTIO
++	help
++	  This enables the virtio based transport for SCMI.
++
++	  If you want to use the ARM SCMI protocol between the virtio guest and
++	  a host providing a virtio SCMI device, answer Y.
++
+ config ARM_SCMI_POWER_DOMAIN
+ 	tristate "SCMI power domain driver"
+ 	depends on ARM_SCMI_PROTOCOL || (COMPILE_TEST && OF)
+diff --git a/drivers/firmware/arm_scmi/Makefile b/drivers/firmware/arm_scmi/Makefile
+index 3cc7fa40a464..25caea5e1969 100644
+--- a/drivers/firmware/arm_scmi/Makefile
++++ b/drivers/firmware/arm_scmi/Makefile
+@@ -4,6 +4,7 @@ scmi-driver-y = driver.o notify.o
+ scmi-transport-$(CONFIG_ARM_SCMI_HAVE_SHMEM) = shmem.o
+ scmi-transport-$(CONFIG_MAILBOX) += mailbox.o
+ scmi-transport-$(CONFIG_HAVE_ARM_SMCCC_DISCOVERY) += smc.o
++scmi-transport-$(CONFIG_VIRTIO_SCMI) += virtio.o
+ scmi-protocols-y = base.o clock.o perf.o power.o reset.o sensors.o system.o
+ scmi-module-objs := $(scmi-bus-y) $(scmi-driver-y) $(scmi-protocols-y) \
+ 		    $(scmi-transport-y)
+diff --git a/drivers/firmware/arm_scmi/common.h b/drivers/firmware/arm_scmi/common.h
+index 13c9ac176b23..b46dfe84e78b 100644
+--- a/drivers/firmware/arm_scmi/common.h
++++ b/drivers/firmware/arm_scmi/common.h
+@@ -165,6 +165,17 @@ int scmi_base_protocol_init(struct scmi_handle *h);
+ int __init scmi_bus_init(void);
+ void __exit scmi_bus_exit(void);
+ 
++#ifdef CONFIG_VIRTIO_SCMI
++int __init virtio_scmi_init(void);
++void __exit virtio_scmi_exit(void);
++#else
++static inline int __init virtio_scmi_init(void)
++{
++	return 0;
++}
++#define virtio_scmi_exit() do { } while (0)
++#endif
++
+ #define DECLARE_SCMI_REGISTER_UNREGISTER(func)		\
+ 	int __init scmi_##func##_register(void);	\
+ 	void __exit scmi_##func##_unregister(void)
+@@ -263,6 +274,9 @@ extern const struct scmi_desc scmi_mailbox_desc;
+ #ifdef CONFIG_HAVE_ARM_SMCCC
+ extern const struct scmi_desc scmi_smc_desc;
+ #endif
++#ifdef CONFIG_VIRTIO_SCMI
++extern const struct scmi_desc scmi_virtio_desc;
++#endif
+ 
+ int scmi_set_transport_info(struct device *dev, void *transport_info);
+ void *scmi_get_transport_info(struct device *dev);
+diff --git a/drivers/firmware/arm_scmi/driver.c b/drivers/firmware/arm_scmi/driver.c
+index 93ce17bb4079..540a55285349 100644
+--- a/drivers/firmware/arm_scmi/driver.c
++++ b/drivers/firmware/arm_scmi/driver.c
+@@ -996,6 +996,9 @@ static const struct of_device_id scmi_of_match[] = {
+ #endif
+ #ifdef CONFIG_HAVE_ARM_SMCCC_DISCOVERY
+ 	{ .compatible = "arm,scmi-smc", .data = &scmi_smc_desc},
++#endif
++#ifdef CONFIG_VIRTIO_SCMI
++	{ .compatible = "arm,scmi-virtio", .data = &scmi_virtio_desc},
+ #endif
+ 	{ /* Sentinel */ },
+ };
+@@ -1014,8 +1017,14 @@ static struct platform_driver scmi_driver = {
+ 
+ static int __init scmi_driver_init(void)
+ {
++	int ret;
++
+ 	scmi_bus_init();
+ 
++	ret = virtio_scmi_init();
++	if (ret)
++		return ret;
++
+ 	scmi_clock_register();
+ 	scmi_perf_register();
+ 	scmi_power_register();
+@@ -1038,6 +1047,8 @@ static void __exit scmi_driver_exit(void)
+ 	scmi_sensors_unregister();
+ 	scmi_system_unregister();
+ 
++	virtio_scmi_exit();
++
+ 	platform_driver_unregister(&scmi_driver);
+ }
+ module_exit(scmi_driver_exit);
+diff --git a/drivers/firmware/arm_scmi/virtio.c b/drivers/firmware/arm_scmi/virtio.c
+new file mode 100644
+index 000000000000..f70aa72f34f1
+--- /dev/null
++++ b/drivers/firmware/arm_scmi/virtio.c
+@@ -0,0 +1,493 @@
++// SPDX-License-Identifier: GPL-2.0
++/*
++ * Virtio Transport driver for Arm System Control and Management Interface
++ * (SCMI).
++ *
++ * Copyright (C) 2020 OpenSynergy.
++ */
++
++/**
++ * DOC: Theory of Operation
++ *
++ * The scmi-virtio transport implements a driver for the virtio SCMI device
++ * proposed in virtio spec patch v5[1].
++ *
++ * There is one tx channel (virtio cmdq, A2P channel) and at most one rx
++ * channel (virtio eventq, P2A channel). Each channel is implemented through a
++ * virtqueue. Access to each virtqueue is protected by a spinlock.
++ *
++ * This SCMI transport uses the scmi_xfer tx/rx buffers for data exchange with
++ * the virtio device to avoid maintenance of additional buffers.
++ *
++ * [1] https://lists.oasis-open.org/archives/virtio-comment/202005/msg00096.html
++ */
++
++#include <linux/errno.h>
++#include <linux/of.h>
++#include <linux/of_platform.h>
++#include <linux/platform_device.h>
++#include <linux/module.h>
++#include <linux/slab.h>
++#include <linux/virtio.h>
++#include <linux/virtio_config.h>
++#include <uapi/linux/virtio_ids.h>
++#include <uapi/linux/virtio_scmi.h>
++
++#include "common.h"
++
++#define VIRTIO_SCMI_MAX_MSG_SIZE 128 /* Value may be increased. */
++#define DESCR_PER_TX_MSG 2
++
++struct scmi_vio_channel {
++	spinlock_t lock;
++	struct virtqueue *vqueue;
++	struct scmi_chan_info *cinfo;
++	u8 is_rx;
++};
++
++union virtio_scmi_input {
++	__virtio32 hdr;
++	struct virtio_scmi_response response;
++	struct virtio_scmi_notification notification;
++};
++
++struct scmi_vio_msg {
++	struct virtio_scmi_request *request;
++	union virtio_scmi_input *input;
++	u8 completed;
++};
++
++static int scmi_vio_populate_vq_rx(struct scmi_vio_channel *vioch,
++				   struct scmi_xfer *xfer)
++{
++	struct scatterlist sg_in;
++	struct scmi_vio_msg *msg = xfer->extra_data;
++	int rc;
++
++	msg->completed = false;
++
++	sg_init_one(&sg_in, msg->input,
++		    sizeof(*msg->input) + VIRTIO_SCMI_MAX_MSG_SIZE);
++
++	rc = virtqueue_add_inbuf(vioch->vqueue, &sg_in, 1, xfer, GFP_ATOMIC);
++	if (rc)
++		dev_err(vioch->cinfo->dev, "%s() rc=%d\n", __func__, rc);
++	else
++		virtqueue_kick(vioch->vqueue);
++
++	return rc;
++}
++
++static void scmi_vio_complete_cb(struct virtqueue *vqueue)
++{
++	struct scmi_vio_channel *vioch = vqueue->priv;
++	unsigned long iflags;
++	unsigned int length;
++
++	spin_lock_irqsave(&vioch->lock, iflags);
++
++	do {
++		struct scmi_xfer *xfer;
++
++		virtqueue_disable_cb(vqueue);
++
++		while ((xfer = virtqueue_get_buf(vqueue, &length))) {
++			struct scmi_vio_msg *msg = xfer->extra_data;
++			u32 msg_hdr =
++				virtio32_to_cpu(vqueue->vdev, msg->input->hdr);
++			u8 msg_type = MSG_XTRACT_TYPE(msg_hdr);
++
++			if (!vioch->is_rx) { /* tx queue response */
++				msg->completed = true;
++				xfer->rx.len =
++					length - sizeof(msg->input->response);
++				if (!xfer->hdr.poll_completion)
++					scmi_rx_callback(vioch->cinfo, msg_hdr);
++				continue;
++			}
++
++			/* rx queue - notification or delayed response */
++			switch (msg_type) {
++			case MSG_TYPE_NOTIFICATION:
++				xfer->rx.len = length -
++					       sizeof(msg->input->notification);
++				xfer->rx.buf = msg->input->notification.data;
++				break;
++			case MSG_TYPE_DELAYED_RESP:
++				xfer->rx.len =
++					length - sizeof(msg->input->response);
++				xfer->rx.buf = msg->input->response.data;
++				break;
++			default:
++				dev_warn_once(vioch->cinfo->dev,
++					      "rx: unknown message_type %d\n",
++					      msg_type);
++				scmi_vio_populate_vq_rx(vioch, xfer);
++				continue;
++			}
++
++			scmi_rx_callback(vioch->cinfo, msg_hdr);
++			scmi_vio_populate_vq_rx(vioch, xfer);
++		}
++
++		if (unlikely(virtqueue_is_broken(vqueue)))
++			break;
++	} while (!virtqueue_enable_cb(vqueue));
++
++	spin_unlock_irqrestore(&vioch->lock, iflags);
++}
++
++static const char *const scmi_vio_vqueue_names[] = { "tx", "rx" };
++
++static vq_callback_t *scmi_vio_complete_callbacks[] = {
++	scmi_vio_complete_cb,
++	scmi_vio_complete_cb
++};
++
++static int scmi_vio_match_any_dev(struct device *dev, const void *data)
++{
++	(void)dev;
++	(void)data;
++
++	return 1;
++}
++
++static struct virtio_driver virtio_scmi_driver; /* Forward declaration */
++
++static int virtio_link_supplier(struct device *dev)
++{
++	struct device *vdev = driver_find_device(
++		&virtio_scmi_driver.driver, NULL, NULL, scmi_vio_match_any_dev);
++
++	if (!vdev) {
++		dev_notice_once(
++			dev,
++			"Deferring probe after not finding a bound scmi-virtio device\n");
++		return -EPROBE_DEFER;
++	}
++
++	/*
++	 * Add plain device link for completeness. It might have no effect
++	 * beyond sysfs.
++	 */
++	if (!device_link_add(dev, vdev, DL_FLAG_AUTOREMOVE_CONSUMER)) {
++		put_device(vdev);
++		dev_err(dev, "Adding link to supplier virtio device failed\n");
++		return -ECANCELED;
++	}
++
++	put_device(vdev);
++	return scmi_set_transport_info(dev, dev_to_virtio(vdev));
++}
++
++static bool virtio_chan_available(struct device *dev, int idx)
++{
++	struct virtio_device *vdev;
++	struct scmi_vio_channel **vioch;
++
++	/* scmi-virtio doesn't support per-protocol channels */
++	if (is_scmi_protocol_device(dev))
++		return false;
++
++	vdev = scmi_get_transport_info(dev);
++	if (!vdev)
++		return false;
++
++	vioch = vdev->priv;
++	if (!vioch)
++		return false;
++
++	return vioch[idx] && vioch[idx]->vqueue;
++}
++
++static int virtio_chan_setup(struct scmi_chan_info *cinfo, struct device *dev,
++			     bool tx)
++{
++	struct virtio_device *vdev;
++	struct scmi_vio_channel **vioch;
++	int vioch_index = tx ? VIRTIO_SCMI_VQ_TX : VIRTIO_SCMI_VQ_RX;
++
++	/* scmi-virtio doesn't support per-protocol channels */
++	if (is_scmi_protocol_device(dev))
++		return -1;
++
++	vdev = scmi_get_transport_info(dev);
++	if (!vdev)
++		return -1;
++
++	vioch = vdev->priv;
++	if (!vioch) {
++		dev_err(dev, "Data from scmi-virtio probe not found\n");
++		return -1;
++	}
++	cinfo->transport_info = vioch[vioch_index];
++	vioch[vioch_index]->cinfo = cinfo;
++
++	return 0;
++}
++
++static int virtio_chan_free(int id, void *p, void *data)
++{
++	struct scmi_chan_info *cinfo = p;
++	struct scmi_vio_channel *vioch = cinfo->transport_info;
++
++	if (vioch) {
++		cinfo->transport_info = NULL;
++		kfree(vioch);
++	}
++
++	scmi_free_channel(cinfo, data, id);
++	return 0;
++}
++
++static int virtio_get_max_msg(bool tx, struct scmi_chan_info *base_cinfo,
++			      int *max_msg)
++{
++	struct scmi_vio_channel *vioch = base_cinfo->transport_info;
++
++	*max_msg = virtqueue_get_vring_size(vioch->vqueue);
++
++	/* Tx messages need multiple descriptors. */
++	if (tx)
++		*max_msg /= DESCR_PER_TX_MSG;
++
++	if (*max_msg > MSG_TOKEN_MAX) {
++		dev_notice(
++			base_cinfo->dev,
++			"Only %ld messages can be pending simultaneously, while the virtqueue could hold %d\n",
++			MSG_TOKEN_MAX, *max_msg);
++		*max_msg = MSG_TOKEN_MAX;
++	}
++
++	return 0;
++}
++
++static int virtio_xfer_init_buffers(struct scmi_chan_info *cinfo,
++				    struct scmi_xfer *xfer, int max_msg_size)
++{
++	struct scmi_vio_channel *vioch = cinfo->transport_info;
++	struct scmi_vio_msg *msg;
++
++	msg = devm_kzalloc(cinfo->dev, sizeof(*msg), GFP_KERNEL);
++	if (!msg)
++		return -ENOMEM;
++
++	xfer->extra_data = msg;
++
++	if (vioch->is_rx) {
++		int rc;
++		unsigned long iflags;
++
++		msg->input = devm_kzalloc(cinfo->dev,
++					  sizeof(*msg->input) + max_msg_size,
++					  GFP_KERNEL);
++		if (!msg->input)
++			return -ENOMEM;
++
++		/*
++		 * xfer->rx.buf will be set to notification or delayed response
++		 * specific values in the receive callback, according to the
++		 * type of the received message.
++		 */
++
++		spin_lock_irqsave(&vioch->lock, iflags);
++		rc = scmi_vio_populate_vq_rx(vioch, xfer);
++		spin_unlock_irqrestore(&vioch->lock, iflags);
++		if (rc)
++			return rc;
++	} else {
++		msg->request =
++			devm_kzalloc(cinfo->dev,
++				     sizeof(*msg->request) + max_msg_size,
++				     GFP_KERNEL);
++		if (!msg->request)
++			return -ENOMEM;
++
++		xfer->tx.buf = msg->request->data;
++
++		msg->input = devm_kzalloc(
++			cinfo->dev, sizeof(msg->input->response) + max_msg_size,
++			GFP_KERNEL);
++		if (!msg->input)
++			return -ENOMEM;
++
++		xfer->rx.buf = msg->input->response.data;
++	}
++
++	return 0;
++}
++
++static int scmi_vio_send(struct scmi_vio_channel *vioch, struct scmi_xfer *xfer)
++{
++	struct scatterlist sg_out;
++	struct scatterlist sg_in;
++	struct scatterlist *sgs[DESCR_PER_TX_MSG] = { &sg_out, &sg_in };
++	struct scmi_vio_msg *msg = xfer->extra_data;
++	unsigned long iflags;
++	int rc;
++
++	msg->completed = false;
++
++	sg_init_one(&sg_out, msg->request,
++		    sizeof(*msg->request) + xfer->tx.len);
++	sg_init_one(&sg_in, &msg->input->response,
++		    sizeof(msg->input->response) + xfer->rx.len);
++
++	spin_lock_irqsave(&vioch->lock, iflags);
++	rc = virtqueue_add_sgs(vioch->vqueue, sgs, 1, 1, xfer, GFP_ATOMIC);
++	if (rc)
++		dev_err(vioch->cinfo->dev, "%s() rc=%d\n", __func__, rc);
++	else
++		virtqueue_kick(vioch->vqueue);
++	spin_unlock_irqrestore(&vioch->lock, iflags);
++
++	return rc;
++}
++
++static int virtio_send_message(struct scmi_chan_info *cinfo,
++			       struct scmi_xfer *xfer)
++{
++	uint32_t hdr;
++	struct scmi_vio_channel *vioch = cinfo->transport_info;
++	struct virtio_device *vdev = vioch->vqueue->vdev;
++	struct scmi_vio_msg *msg = xfer->extra_data;
++
++	hdr = pack_scmi_header(&xfer->hdr);
++
++	msg->request->hdr = cpu_to_virtio32(vdev, hdr);
++
++	return scmi_vio_send(vioch, xfer);
++}
++
++static void virtio_fetch_response(struct scmi_chan_info *cinfo,
++				  struct scmi_xfer *xfer)
++{
++	struct scmi_vio_channel *vioch = cinfo->transport_info;
++	struct scmi_vio_msg *msg = xfer->extra_data;
++
++	xfer->hdr.status = virtio32_to_cpu(vioch->vqueue->vdev,
++					   msg->input->response.status);
++}
++
++static void dummy_fetch_notification(struct scmi_chan_info *cinfo,
++				     size_t max_len, struct scmi_xfer *xfer)
++{
++	(void)cinfo;
++	(void)max_len;
++	(void)xfer;
++}
++
++static void dummy_clear_channel(struct scmi_chan_info *cinfo)
++{
++	(void)cinfo;
++}
++
++static bool virtio_poll_done(struct scmi_chan_info *cinfo,
++			     struct scmi_xfer *xfer)
++{
++	struct scmi_vio_channel *vioch = cinfo->transport_info;
++	struct scmi_vio_msg *msg = xfer->extra_data;
++	unsigned long iflags;
++	bool completed;
++
++	spin_lock_irqsave(&vioch->lock, iflags);
++	completed = msg->completed;
++	spin_unlock_irqrestore(&vioch->lock, iflags);
++
++	return completed;
++}
++
++static const struct scmi_transport_ops scmi_virtio_ops = {
++	.link_supplier = virtio_link_supplier,
++	.chan_available = virtio_chan_available,
++	.chan_setup = virtio_chan_setup,
++	.chan_free = virtio_chan_free,
++	.get_max_msg = virtio_get_max_msg,
++	.send_message = virtio_send_message,
++	.fetch_response = virtio_fetch_response,
++	.fetch_notification = dummy_fetch_notification,
++	.clear_channel = dummy_clear_channel,
++	.poll_done = virtio_poll_done,
++	.xfer_init_buffers = virtio_xfer_init_buffers,
++};
++
++const struct scmi_desc scmi_virtio_desc = {
++	.ops = &scmi_virtio_ops,
++	.max_rx_timeout_ms = 60000, /* for non-realtime virtio devices */
++	.max_msg = 0, /* overridden by virtio_get_max_msg() */
++	.max_msg_size = VIRTIO_SCMI_MAX_MSG_SIZE,
++};
++
++static int scmi_vio_probe(struct virtio_device *vdev)
++{
++	struct device *dev = &vdev->dev;
++	struct scmi_vio_channel **vioch;
++	bool have_vq_rx;
++	int vq_cnt;
++	int i;
++	struct virtqueue *vqs[VIRTIO_SCMI_VQ_MAX_CNT];
++
++	vioch = devm_kcalloc(dev, VIRTIO_SCMI_VQ_MAX_CNT, sizeof(*vioch),
++			     GFP_KERNEL);
++	if (!vioch)
++		return -ENOMEM;
++
++	have_vq_rx = virtio_has_feature(vdev, VIRTIO_SCMI_F_P2A_CHANNELS);
++	vq_cnt = have_vq_rx ? VIRTIO_SCMI_VQ_MAX_CNT : 1;
++
++	for (i = 0; i < vq_cnt; i++) {
++		vioch[i] = devm_kzalloc(dev, sizeof(**vioch), GFP_KERNEL);
++		if (!vioch[i])
++			return -ENOMEM;
++	}
++
++	if (have_vq_rx)
++		vioch[VIRTIO_SCMI_VQ_RX]->is_rx = true;
++
++	if (virtio_find_vqs(vdev, vq_cnt, vqs, scmi_vio_complete_callbacks,
++			    scmi_vio_vqueue_names, NULL)) {
++		dev_err(dev, "Failed to get %d virtqueue(s)\n", vq_cnt);
++		return -1;
++	}
++	dev_info(dev, "Found %d virtqueue(s)\n", vq_cnt);
++
++	for (i = 0; i < vq_cnt; i++) {
++		spin_lock_init(&vioch[i]->lock);
++		vioch[i]->vqueue = vqs[i];
++		vioch[i]->vqueue->priv = vioch[i];
++	}
++
++	vdev->priv = vioch;
++
++	virtio_device_ready(vdev);
++
++	return 0;
++}
++
++static unsigned int features[] = {
++	VIRTIO_SCMI_F_P2A_CHANNELS,
++};
++
++static const struct virtio_device_id id_table[] = {
++	{ VIRTIO_ID_SCMI, VIRTIO_DEV_ANY_ID },
++	{ 0 }
++};
++
++static struct virtio_driver virtio_scmi_driver = {
++	.driver.name = "scmi-virtio",
++	.driver.owner = THIS_MODULE,
++	.feature_table = features,
++	.feature_table_size = ARRAY_SIZE(features),
++	.id_table = id_table,
++	.probe = scmi_vio_probe,
++};
++
++int __init virtio_scmi_init(void)
++{
++	return register_virtio_driver(&virtio_scmi_driver);
++}
++
++void __exit virtio_scmi_exit(void)
++{
++	unregister_virtio_driver(&virtio_scmi_driver);
++}
+diff --git a/include/uapi/linux/virtio_ids.h b/include/uapi/linux/virtio_ids.h
+index bc740d6d2259..287daba2abdb 100644
+--- a/include/uapi/linux/virtio_ids.h
++++ b/include/uapi/linux/virtio_ids.h
+@@ -49,5 +49,6 @@
+ #define VIRTIO_ID_FS           26 /* virtio filesystem */
+ #define VIRTIO_ID_PMEM         27 /* virtio pmem */
+ #define VIRTIO_ID_MAC80211_HWSIM 29 /* virtio mac80211-hwsim */
++#define VIRTIO_ID_SCMI         32 /* virtio SCMI */
+ 
+ #endif /* _LINUX_VIRTIO_IDS_H */
+diff --git a/include/uapi/linux/virtio_scmi.h b/include/uapi/linux/virtio_scmi.h
+new file mode 100644
+index 000000000000..9f21b3dbbfe2
+--- /dev/null
++++ b/include/uapi/linux/virtio_scmi.h
+@@ -0,0 +1,41 @@
++/* SPDX-License-Identifier: ((GPL-2.0 WITH Linux-syscall-note) OR BSD-3-Clause) */
++/*
++ * Copyright (C) 2020 OpenSynergy GmbH
++ */
++
++#ifndef _UAPI_LINUX_VIRTIO_SCMI_H
++#define _UAPI_LINUX_VIRTIO_SCMI_H
++
++#include <linux/virtio_types.h>
++
++/* Feature bits */
++
++/* Device implements some SCMI notifications, or delayed responses. */
++#define VIRTIO_SCMI_F_P2A_CHANNELS 0
++
++/* Device implements any SCMI statistics shared memory region */
++#define VIRTIO_SCMI_F_SHARED_MEMORY 1
++
++/* Virtqueues */
++
++#define VIRTIO_SCMI_VQ_TX 0 /* cmdq */
++#define VIRTIO_SCMI_VQ_RX 1 /* eventq */
++#define VIRTIO_SCMI_VQ_MAX_CNT 2
++
++struct virtio_scmi_request {
++	__virtio32 hdr;
++	__u8 data[];
++};
++
++struct virtio_scmi_response {
++	__virtio32 hdr;
++	__virtio32 status;
++	__u8 data[];
++};
++
++struct virtio_scmi_notification {
++	__virtio32 hdr;
++	__u8 data[];
++};
++
++#endif /* _UAPI_LINUX_VIRTIO_SCMI_H */