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From 4ebcbe09471d6b6b18fce42993489bed3801f10c Mon Sep 17 00:00:00 2001
From: Jean-Philippe Brucker <jean-philippe@linaro.org>
Date: Fri, 24 Jan 2020 10:17:14 +0100
Subject: [PATCH 1/4] TMP: iommu/arm-smmu-v3: Ignore IOPF capabilities
Don't mandate PRI or stall to enable SVA. Some devices have their own
method for managing I/O page faults when they notice a translation
request that fails.
Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
---
drivers/iommu/arm-smmu-v3.c | 18 +++++++++++++++++-
1 file changed, 17 insertions(+), 1 deletion(-)
diff --git a/drivers/iommu/arm-smmu-v3.c b/drivers/iommu/arm-smmu-v3.c
index fed6a9d5867e..a8d7d6ccbb21 100644
--- a/drivers/iommu/arm-smmu-v3.c
+++ b/drivers/iommu/arm-smmu-v3.c
@@ -3276,7 +3276,23 @@ static bool arm_smmu_ats_supported(struct arm_smmu_master *master)
static bool arm_smmu_iopf_supported(struct arm_smmu_master *master)
{
- return master->stall_enabled || master->pri_supported;
+ /* return master->stall_enabled || master->pri_supported; */
+
+ /*
+ * FIXME: this temporary hack allows enabling SVA for any endpoint even
+ * when they don't have PRI/stall.
+ *
+ * To implement this more cleanly, we need a third method, complementing
+ * stall_enabled and pri_supported, to enable IOPF. A bit that says
+ * "this device's page faults are handled out of band", called for
+ * example master->oob_iopf. How to set it? It can easily be a firmware
+ * quirk, but that does not suffice in my opinion. We need to know that
+ * there is software ready to handle these page faults. The device
+ * driver owning this endpoint could for example call
+ * iommu_dev_enable_feature(dev, IOMMU_DEV_FEAT_OOB_IOPF), before
+ * enabling IOMMU_DEV_FEAT_SVA.
+ */
+ return true;
}
static void arm_smmu_enable_ats(struct arm_smmu_master *master)
--
2.25.0
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