linux-agl: add pfifo patchset for fixing CAN failures

Backported upstream patchset to fix CAN failures with SocketCAN

* net: sch_generic: Use pfifo_fast as fallback scheduler for CAN hardware

Additional patchset for 4.14 kernels to bring in needed if_afp.h header

Bug-AGL: SPEC-3171
Change-Id: I1ddb75d1aca64861cfc52f1df4ff810bd0367ab9
Signed-off-by: Matt Ranostay <matt.ranostay@konsulko.com>

4 files changed, 109 insertions, 0 deletions

diff --git a/meta-agl-bsp/recipes-kernel/linux/linux-4.14/net-sch_generic-add-if_afp.h-header-to-get-ARPHRD_CA.patch b/meta-agl-bsp/recipes-kernel/linux/linux-4.14/net-sch_generic-add-if_afp.h-header-to-get-ARPHRD_CA.patch
new file mode 100644
index 000000000..7c34fb306
--- /dev/null
+++ b/meta-agl-bsp/recipes-kernel/linux/linux-4.14/net-sch_generic-add-if_afp.h-header-to-get-ARPHRD_CA.patch
@@ -0,0 +1,25 @@
+From 17d0075d95b5087d5df553444cca390fa479bad9 Mon Sep 17 00:00:00 2001
+From: Matt Ranostay <matt.ranostay@konsulko.com>
+Date: Tue, 10 Mar 2020 22:27:28 -0700
+Subject: [PATCH] net: sch_generic: add if_afp.h header to get ARPHRD_CAN macro
+
+Signed-off-by: Matt Ranostay <matt.ranostay@konsulko.com>
+---
+ net/sched/sch_generic.c | 1 +
+ 1 file changed, 1 insertion(+)
+
+diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c
+index bf8c81e07c70..1845ef8c7dbd 100644
+--- a/net/sched/sch_generic.c
++++ b/net/sched/sch_generic.c
+@@ -25,6 +25,7 @@
+ #include <linux/rcupdate.h>
+ #include <linux/list.h>
+ #include <linux/slab.h>
++#include <linux/if_arp.h>
+ #include <linux/if_vlan.h>
+ #include <net/sch_generic.h>
+ #include <net/pkt_sched.h>
+-- 
+2.25.0
+
diff --git a/meta-agl-bsp/recipes-kernel/linux/linux-agl-4.14.inc b/meta-agl-bsp/recipes-kernel/linux/linux-agl-4.14.inc
index 87249bdcd..8521b1d6c 100644
--- a/meta-agl-bsp/recipes-kernel/linux/linux-agl-4.14.inc
+++ b/meta-agl-bsp/recipes-kernel/linux/linux-agl-4.14.inc
@@ -8,3 +8,6 @@ SRC_URI_append_with-lsm-smack = "\
        file://Smack-Handle-CGROUP2-in-the-same-way-that-CGROUP.patch \
        "
 
+SRC_URI_append = "\
+       file://net-sch_generic-add-if_afp.h-header-to-get-ARPHRD_CA.patch \
+       "
diff --git a/meta-agl-bsp/recipes-kernel/linux/linux-agl.inc b/meta-agl-bsp/recipes-kernel/linux/linux-agl.inc
index c03c56ea3..74dadf66e 100644
--- a/meta-agl-bsp/recipes-kernel/linux/linux-agl.inc
+++ b/meta-agl-bsp/recipes-kernel/linux/linux-agl.inc
@@ -2,6 +2,12 @@ FILESEXTRAPATHS_prepend := "${THISDIR}/linux:"
 
 DEPENDS += "kern-tools-native"
 
+# canbus qdisc pfifo change
+SRC_URI_append = " file://net-sch_generic-Use-pfifo_fast-as-fallback-scheduler.patch"
+
+# bbe target has this upstream patch already
+SRC_URI_remove_bbe = " file://net-sch_generic-Use-pfifo_fast-as-fallback-scheduler.patch"
+
 # returns all the elements from the src uri that are .cfg files
 def find_cfgs(d):
     sources=src_patches(d, True)
diff --git a/meta-agl-bsp/recipes-kernel/linux/linux/net-sch_generic-Use-pfifo_fast-as-fallback-scheduler.patch b/meta-agl-bsp/recipes-kernel/linux/linux/net-sch_generic-Use-pfifo_fast-as-fallback-scheduler.patch
new file mode 100644
index 000000000..37ace5a58
--- /dev/null
+++ b/meta-agl-bsp/recipes-kernel/linux/linux/net-sch_generic-Use-pfifo_fast-as-fallback-scheduler.patch
@@ -0,0 +1,75 @@
+From 546b85bb0aadb5a928b49b53dc02911996169c0b Mon Sep 17 00:00:00 2001
+From: Vincent Prince <vincent.prince.fr@gmail.com>
+Date: Wed, 23 Oct 2019 15:44:20 +0200
+Subject: [PATCH] net: sch_generic: Use pfifo_fast as fallback scheduler for
+ CAN hardware
+
+There is networking hardware that isn't based on Ethernet for layers 1 and 2.
+
+For example CAN.
+
+CAN is a multi-master serial bus standard for connecting Electronic Control
+Units [ECUs] also known as nodes. A frame on the CAN bus carries up to 8 bytes
+of payload. Frame corruption is detected by a CRC. However frame loss due to
+corruption is possible, but a quite unusual phenomenon.
+
+While fq_codel works great for TCP/IP, it doesn't for CAN. There are a lot of
+legacy protocols on top of CAN, which are not build with flow control or high
+CAN frame drop rates in mind.
+
+When using fq_codel, as soon as the queue reaches a certain delay based length,
+skbs from the head of the queue are silently dropped. Silently meaning that the
+user space using a send() or similar syscall doesn't get an error. However
+TCP's flow control algorithm will detect dropped packages and adjust the
+bandwidth accordingly.
+
+When using fq_codel and sending raw frames over CAN, which is the common use
+case, the user space thinks the package has been sent without problems, because
+send() returned without an error. pfifo_fast will drop skbs, if the queue
+length exceeds the maximum. But with this scheduler the skbs at the tail are
+dropped, an error (-ENOBUFS) is propagated to user space. So that the user
+space can slow down the package generation.
+
+On distributions, where fq_codel is made default via CONFIG_DEFAULT_NET_SCH
+during compile time, or set default during runtime with sysctl
+net.core.default_qdisc (see [1]), we get a bad user experience. In my test case
+with pfifo_fast, I can transfer thousands of million CAN frames without a frame
+drop. On the other hand with fq_codel there is more then one lost CAN frame per
+thousand frames.
+
+As pointed out fq_codel is not suited for CAN hardware, so this patch changes
+attach_one_default_qdisc() to use pfifo_fast for "ARPHRD_CAN" network devices.
+
+During transition of a netdev from down to up state the default queuing
+discipline is attached by attach_default_qdiscs() with the help of
+attach_one_default_qdisc(). This patch modifies attach_one_default_qdisc() to
+attach the pfifo_fast (pfifo_fast_ops) if the network device type is
+"ARPHRD_CAN".
+
+[1] https://github.com/systemd/systemd/issues/9194
+
+Suggested-by: Marc Kleine-Budde <mkl@pengutronix.de>
+Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
+Signed-off-by: Vincent Prince <vincent.prince.fr@gmail.com>
+Acked-by: Dave Taht <dave.taht@gmail.com>
+Signed-off-by: David S. Miller <davem@davemloft.net>
+---
+ net/sched/sch_generic.c | 2 ++
+ 1 file changed, 2 insertions(+)
+
+diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c
+index ed5b0e9fd395..4c5dfcb01e00 100644
+--- a/net/sched/sch_generic.c
++++ b/net/sched/sch_generic.c
+@@ -1038,6 +1038,8 @@ static void attach_one_default_qdisc(struct net_device *dev,
+ 
+ 	if (dev->priv_flags & IFF_NO_QUEUE)
+ 		ops = &noqueue_qdisc_ops;
++	else if(dev->type == ARPHRD_CAN)
++		ops = &pfifo_fast_ops;
+ 
+ 	qdisc = qdisc_create_dflt(dev_queue, ops, TC_H_ROOT, NULL);
+ 	if (!qdisc) {
+-- 
+2.25.0
+