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From:   Eric Anholt <eric@anholt.net>
To:     dri-devel@lists.freedesktop.org, linux-arm-msm@vger.kernel.org,
        freedreno@lists.freedesktop.org, Rob Clark <robdclark@gmail.com>,
        Sean Paul <sean@poorly.run>,
        Jordan Crouse <jcrouse@codeaurora.org>,
        Robin Murphy <robin.murphy@arm.com>,
        Will Deacon <will@kernel.org>,
        Rob Herring <robh+dt@kernel.org>,
        Joerg Roedel <joro@8bytes.org>,
        linux-arm-kernel@lists.infradead.org, devicetree@vger.kernel.org
Cc:     linux-kernel@vger.kernel.org, Eric Anholt <eric@anholt.net>
Subject: [PATCH 1/2] iommu/arm-smmu-qcom: Skip the TTBR1 quirk for db820c.
Date:   Fri, 26 Mar 2021 16:13:02 -0700
Message-Id: <20210326231303.3071950-1-eric@anholt.net>
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Precedence: bulk

db820c wants to use the qcom smmu path to get HUPCF set (which keeps
the GPU from wedging and then sometimes wedging the kernel after a
page fault), but it doesn't have separate pagetables support yet in
drm/msm so we can't go all the way to the TTBR1 path.

Signed-off-by: Eric Anholt <eric@anholt.net>
---

We've been seeing a flaky test per day or so in Mesa CI where the
kernel gets wedged after an iommu fault turns into CP errors.  With
this patch, the CI isn't throwing the string of CP errors on the
faults in any of the ~10 jobs I've run so far.

 drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c b/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c
index bcda17012aee..51f22193e456 100644
--- a/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c
+++ b/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c
@@ -130,6 +130,16 @@ static int qcom_adreno_smmu_alloc_context_bank(struct arm_smmu_domain *smmu_doma
 	return __arm_smmu_alloc_bitmap(smmu->context_map, start, count);
 }
 
+static bool qcom_adreno_can_do_ttbr1(struct arm_smmu_device *smmu)
+{
+	const struct device_node *np = smmu->dev->of_node;
+
+	if (of_device_is_compatible(np, "qcom,msm8996-smmu-v2"))
+		return false;
+
+	return true;
+}
+
 static int qcom_adreno_smmu_init_context(struct arm_smmu_domain *smmu_domain,
 		struct io_pgtable_cfg *pgtbl_cfg, struct device *dev)
 {
@@ -144,7 +154,8 @@ static int qcom_adreno_smmu_init_context(struct arm_smmu_domain *smmu_domain,
 	 * be AARCH64 stage 1 but double check because the arm-smmu code assumes
 	 * that is the case when the TTBR1 quirk is enabled
 	 */
-	if ((smmu_domain->stage == ARM_SMMU_DOMAIN_S1) &&
+	if (qcom_adreno_can_do_ttbr1(smmu_domain->smmu) &&
+	    (smmu_domain->stage == ARM_SMMU_DOMAIN_S1) &&
 	    (smmu_domain->cfg.fmt == ARM_SMMU_CTX_FMT_AARCH64))
 		pgtbl_cfg->quirks |= IO_PGTABLE_QUIRK_ARM_TTBR1;
 
-- 
2.31.0