linux-kernel - [PATCH 1/2] iommu/arm-smmu-v3: Match Stall behaviour for S2

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Message-ID: <20240812205255.97781-2-smostafa@google.com>
Date: Mon, 12 Aug 2024 20:52:54 +0000
From: Mostafa Saleh <smostafa@...gle.com>
To: linux-kernel@...r.kernel.org, iommu@...ts.linux.dev, 
	linux-arm-kernel@...ts.infradead.org, will@...nel.org, robin.murphy@....com, 
	joro@...tes.org
Cc: jgg@...pe.ca, nicolinc@...dia.com, mshavit@...gle.com, 
	Mostafa Saleh <smostafa@...gle.com>
Subject: [PATCH 1/2] iommu/arm-smmu-v3: Match Stall behaviour for S2

S2S must be set when stall model is forced "ARM_SMMU_FEAT_STALL_FORCE".
But at the moment the driver ignores that, instead of doing the minimum
and only set S2S for “ARM_SMMU_FEAT_STALL_FORCE” we can just match what
S1 does which also set it for “ARM_SMMU_FEAT_STALL” and the master
has requested stalls.
This makes the driver more consistent when running on different SMMU
instances with different supported stages.

Signed-off-by: Mostafa Saleh <smostafa@...gle.com>
---
 drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 5 +++++
 drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h | 1 +
 2 files changed, 6 insertions(+)

diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
index a31460f9f3d4..8d573d9ca93c 100644
--- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
+++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
@@ -1562,6 +1562,11 @@ void arm_smmu_make_cdtable_ste(struct arm_smmu_ste *target,
 		(cd_table->cdtab_dma & STRTAB_STE_0_S1CTXPTR_MASK) |
 		FIELD_PREP(STRTAB_STE_0_S1CDMAX, cd_table->s1cdmax));
 
+	/* S2S is ignored if stage-2 exists but not enabled. */
+	if (master->stall_enabled &&
+	    smmu->features & ARM_SMMU_FEAT_TRANS_S2)
+		target->data[0] |= FIELD_PREP(STRTAB_STE_2_S2S, 1);
+
 	target->data[1] = cpu_to_le64(
 		FIELD_PREP(STRTAB_STE_1_S1DSS, s1dss) |
 		FIELD_PREP(STRTAB_STE_1_S1CIR, STRTAB_STE_1_S1C_CACHE_WBRA) |
diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
index 14bca41a981b..0dc7ad43c64c 100644
--- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
+++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
@@ -267,6 +267,7 @@ struct arm_smmu_ste {
 #define STRTAB_STE_2_S2AA64		(1UL << 51)
 #define STRTAB_STE_2_S2ENDI		(1UL << 52)
 #define STRTAB_STE_2_S2PTW		(1UL << 54)
+#define STRTAB_STE_2_S2S		(1UL << 57)
 #define STRTAB_STE_2_S2R		(1UL << 58)
 
 #define STRTAB_STE_3_S2TTB_MASK		GENMASK_ULL(51, 4)
-- 
2.46.0.76.ge559c4bf1a-goog