[PATCH] iommu/arm-smmu: Don't bypass pinned stream mappings

[Jordan Crouse]

Commit 0e764a01015d ("iommu/arm-smmu: Allow client devices to select
direct mapping") sets the initial domain type to SMMU_DOMAIN_IDENTITY
for devices that select direct mapping. This ends up setting the domain
as ARM_SMMU_DOMAIN_BYPASS which causes the stream ID mappings
for the device to be programmed to S2CR_TYPE_BYPASS.

This causes a problem for stream mappings that are inherited from
the bootloader since rewriting the stream to BYPASS will disrupt the
display controller access to DDR.

This is an extension to ("iommu/arm-smmu: Allow inheriting stream mapping
from bootloader") [1] that identifies streams that are already configured
 and marked them as pinned. This patch extends that to not re-write pinned
stream mappings for ARM_SMMU_DOMAIN_BYPASS domains.

[1] https://lore.kernel.org/r/20191226221709.3844244-4-bjorn.andersson@xxxxxxxxxx

Signed-off-by: Jordan Crouse <jcrouse@xxxxxxxxxxxxxx>
---

 drivers/iommu/arm-smmu.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/iommu/arm-smmu.c b/drivers/iommu/arm-smmu.c
index c7add09f11c1..9c1e5ba948a7 100644
--- a/drivers/iommu/arm-smmu.c
+++ b/drivers/iommu/arm-smmu.c
@@ -1143,6 +1143,10 @@ static int arm_smmu_domain_add_master(struct arm_smmu_domain *smmu_domain,
 		if (type == s2cr[idx].type && cbndx == s2cr[idx].cbndx)
 			continue;
 
+		/* Don't bypasss pinned streams; leave them as they are */
+		if (type == S2CR_TYPE_BYPASS && s2cr[idx].pinned)
+			continue;
+
 		s2cr[idx].type = type;
 		s2cr[idx].privcfg = S2CR_PRIVCFG_DEFAULT;
 		s2cr[idx].cbndx = cbndx;
-- 
2.17.1