linux-kernel - [PATCH] iommu/arm-smmu: Warn once when the perfetcher errata patch fails to apply

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Message-Id: <20221103222121.3051-1-chen45464546@163.com>
Date:   Fri,  4 Nov 2022 06:21:21 +0800
From:   Chen Lin <chen45464546@....com>
To:     will@...nel.org
Cc:     robin.murphy@....com, joro@...tes.org, treding@...dia.com,
        linux-arm-kernel@...ts.infradead.org, iommu@...ts.linux.dev,
        linux-kernel@...r.kernel.org, Chen Lin <chen45464546@....com>
Subject: [PATCH] iommu/arm-smmu: Warn once when the perfetcher errata patch fails to apply

Default reset value of secure banked register SMMU_sACR.cache_lock is 1.
If it is not been set to 0 by secure software(eg: atf), the non-secure 
linux cannot clear ARM_MMU500_ACTLR_CPRE bit. In this situation,
the prefetcher errata is not applied successfully, warn once.

Signed-off-by: Chen Lin <chen45464546@....com>
---
 drivers/iommu/arm/arm-smmu/arm-smmu-impl.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/iommu/arm/arm-smmu/arm-smmu-impl.c b/drivers/iommu/arm/arm-smmu/arm-smmu-impl.c
index 658f3cc83278..2d2252b3e518 100644
--- a/drivers/iommu/arm/arm-smmu/arm-smmu-impl.c
+++ b/drivers/iommu/arm/arm-smmu/arm-smmu-impl.c
@@ -136,6 +136,9 @@ int arm_mmu500_reset(struct arm_smmu_device *smmu)
 		reg = arm_smmu_cb_read(smmu, i, ARM_SMMU_CB_ACTLR);
 		reg &= ~ARM_MMU500_ACTLR_CPRE;
 		arm_smmu_cb_write(smmu, i, ARM_SMMU_CB_ACTLR, reg);
+		reg = arm_smmu_cb_read(smmu, i, ARM_SMMU_CB_ACTLR);
+		if (reg & ARM_MMU500_ACTLR_CPRE)
+			dev_warn_once(smmu->dev, "Failed to alpply prefetcher errata patch, check SMMU_sACR.cache_lock\n");
 	}
 
 	return 0;
-- 
2.25.1