linux-kernel - [PATCH v2] iommu/arm-smmu-qcom: Only enable stall on smmu-v2

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Message-ID: <20250102183232.115279-1-robdclark@gmail.com>
Date: Thu,  2 Jan 2025 10:32:31 -0800
From: Rob Clark <robdclark@...il.com>
To: iommu@...ts.linux.dev
Cc: linux-arm-msm@...r.kernel.org,
	freedreno@...ts.freedesktop.org,
	Robin Murphy <robin.murphy@....com>,
	Will Deacon <will@...nel.org>,
	Rob Clark <robdclark@...omium.org>,
	Rob Clark <robdclark@...il.com>,
	Joerg Roedel <joro@...tes.org>,
	linux-arm-kernel@...ts.infradead.org (moderated list:ARM SMMU DRIVERS),
	linux-kernel@...r.kernel.org (open list)
Subject: [PATCH v2] iommu/arm-smmu-qcom: Only enable stall on smmu-v2

From: Rob Clark <robdclark@...omium.org>

On mmu-500, stall-on-fault seems to stall all context banks, causing the
GMU to misbehave.  So limit this feature to smmu-v2 for now.

This fixes an issue with an older mesa bug taking outo the system
because of GMU going off into the weeds.

What we _think_ is happening is that, if the GPU generates 1000's of
faults at ~once (which is something that GPUs can be good at), it can
result in a sufficient number of stalled translations preventing other
transactions from entering the same TBU.

Signed-off-by: Rob Clark <robdclark@...omium.org>
---
v2: Adds a modparam to override the default behavior, for debugging
    GPU faults in cases which do not (or might not) cause lockup.
    Also, rebased to not depend on Bibek's PRR support.

 drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c | 19 +++++++++++++++++--
 1 file changed, 17 insertions(+), 2 deletions(-)

diff --git a/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c b/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c
index 6372f3e25c4b..3239bbf18514 100644
--- a/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c
+++ b/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c
@@ -16,6 +16,10 @@
 
 #define QCOM_DUMMY_VAL	-1
 
+static int enable_stall = -1;
+MODULE_PARM_DESC(enable_stall, "Enable stall on iova fault (1=on , 0=disable, -1=auto (default))");
+module_param(enable_stall, int, 0600);
+
 static struct qcom_smmu *to_qcom_smmu(struct arm_smmu_device *smmu)
 {
 	return container_of(smmu, struct qcom_smmu, smmu);
@@ -210,7 +214,9 @@ static bool qcom_adreno_can_do_ttbr1(struct arm_smmu_device *smmu)
 static int qcom_adreno_smmu_init_context(struct arm_smmu_domain *smmu_domain,
 		struct io_pgtable_cfg *pgtbl_cfg, struct device *dev)
 {
+	const struct device_node *np = smmu_domain->smmu->dev->of_node;
 	struct adreno_smmu_priv *priv;
+	bool stall_enabled;
 
 	smmu_domain->cfg.flush_walk_prefer_tlbiasid = true;
 
@@ -237,8 +243,17 @@ static int qcom_adreno_smmu_init_context(struct arm_smmu_domain *smmu_domain,
 	priv->get_ttbr1_cfg = qcom_adreno_smmu_get_ttbr1_cfg;
 	priv->set_ttbr0_cfg = qcom_adreno_smmu_set_ttbr0_cfg;
 	priv->get_fault_info = qcom_adreno_smmu_get_fault_info;
-	priv->set_stall = qcom_adreno_smmu_set_stall;
-	priv->resume_translation = qcom_adreno_smmu_resume_translation;
+
+	if (enable_stall < 0) {
+		stall_enabled = of_device_is_compatible(np, "qcom,smmu-v2");
+	} else {
+		stall_enabled = !!enable_stall;
+	}
+
+	if (stall_enabled) {
+		priv->set_stall = qcom_adreno_smmu_set_stall;
+		priv->resume_translation = qcom_adreno_smmu_resume_translation;
+	}
 
 	return 0;
 }
-- 
2.47.1