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

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Date:   Tue,  9 Jun 2020 12:05:16 -0600
From:   Jordan Crouse <jcrouse@...eaurora.org>
To:     linux-arm-msm@...r.kernel.org
Cc:     Patrick Daly <pdaly@...eaurora.org>,
        linux-arm-kernel@...ts.infradead.org,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Sai Prakash Ranjan <saiprakash.ranjan@...eaurora.org>,
        Joerg Roedel <joro@...tes.org>,
        Robin Murphy <robin.murphy@....com>,
        Will Deacon <will@...nel.org>,
        iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org
Subject: [PATCH] iommu/arm-smmu: Don't bypass pinned stream mappings

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@linaro.org

Signed-off-by: Jordan Crouse <jcrouse@...eaurora.org>
---

 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