linux-kernel - [PATCH] iommu/arm-smmu-v3: Simplify stage selection logic

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Date:   Fri, 18 Aug 2023 00:03:30 +0800
From:   Michael Shavit <mshavit@...gle.com>
To:     iommu@...ts.linux.dev
Cc:     Michael Shavit <mshavit@...gle.com>,
        Jason Gunthorpe <jgg@...pe.ca>,
        Jean-Philippe Brucker <jean-philippe@...aro.org>,
        Joerg Roedel <joro@...tes.org>,
        Lu Baolu <baolu.lu@...ux.intel.com>,
        Nicolin Chen <nicolinc@...dia.com>,
        Robin Murphy <robin.murphy@....com>,
        Tomas Krcka <krckatom@...zon.de>,
        Will Deacon <will@...nel.org>,
        Yicong Yang <yangyicong@...ilicon.com>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: [PATCH] iommu/arm-smmu-v3: Simplify stage selection logic

It is invalid for an arm-smmu-v3 to have neither FEAT_TRANS_S1 nor
FEAT_TRANS_S2 bits set, and this is even checked in the probe.

Only set ARM_SMMU_DOMAIN_S2 if FEAT_TRANS_S1 isn't supported, otherwise set
ARM_SMMU_DOMAIN_S1. This is clearer as the existing code implies that
something more sophisticated is going on with the stage selection logic.

Signed-off-by: Michael Shavit <mshavit@...gle.com>
---

 drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

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 9b0dc35056019..e74c8c630adfa 100644
--- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
+++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
@@ -2206,7 +2206,7 @@ static int arm_smmu_domain_finalise(struct iommu_domain *domain,
 	/* Restrict the stage to what we can actually support */
 	if (!(smmu->features & ARM_SMMU_FEAT_TRANS_S1))
 		smmu_domain->stage = ARM_SMMU_DOMAIN_S2;
-	if (!(smmu->features & ARM_SMMU_FEAT_TRANS_S2))
+	else
 		smmu_domain->stage = ARM_SMMU_DOMAIN_S1;
 
 	switch (smmu_domain->stage) {

base-commit: 6eaae198076080886b9e7d57f4ae06fa782f90ef
-- 
2.41.0.694.ge786442a9b-goog