linux-kernel - [PATCH v3 1/4] iommu/arm-smmu: Add SMMU ID2 register fixup hook

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Date:   Thu,  2 Jul 2020 22:16:30 +0200
From:   Tomasz Nowicki <tn@...ihalf.com>
To:     will@...nel.org, robin.murphy@....com, joro@...tes.org,
        gregory.clement@...tlin.com, robh+dt@...nel.org, hannah@...vell.com
Cc:     linux-kernel@...r.kernel.org, iommu@...ts.linux-foundation.org,
        devicetree@...r.kernel.org, catalin.marinas@....com,
        nadavh@...vell.com, linux-arm-kernel@...ts.infradead.org,
        mw@...ihalf.com, Tomasz Nowicki <tn@...ihalf.com>
Subject: [PATCH v3 1/4] iommu/arm-smmu: Add SMMU ID2 register fixup hook

We already have 'cfg_probe' hook which meant to override and apply
workarounds while probing ID registers. However, 'cfg_probe' is called
at the very end and therefore for some cases fixing up things becomes complex
or requires exporting of SMMU driver structures. Hence, seems it is better and
cleaner to do ID fixup right away. In preparation for adding Marvell
errata add an extra ID2 fixup hook.

Signed-off-by: Tomasz Nowicki <tn@...ihalf.com>
---
 drivers/iommu/arm-smmu.c | 3 +++
 drivers/iommu/arm-smmu.h | 1 +
 2 files changed, 4 insertions(+)

diff --git a/drivers/iommu/arm-smmu.c b/drivers/iommu/arm-smmu.c
index 243bc4cb2705..17c92e319754 100644
--- a/drivers/iommu/arm-smmu.c
+++ b/drivers/iommu/arm-smmu.c
@@ -1857,6 +1857,9 @@ static int arm_smmu_device_cfg_probe(struct arm_smmu_device *smmu)
 
 	/* ID2 */
 	id = arm_smmu_gr0_read(smmu, ARM_SMMU_GR0_ID2);
+	if (smmu->impl && smmu->impl->cfg_id2_fixup)
+		id = smmu->impl->cfg_id2_fixup(id);
+
 	size = arm_smmu_id_size_to_bits(FIELD_GET(ARM_SMMU_ID2_IAS, id));
 	smmu->ipa_size = size;
 
diff --git a/drivers/iommu/arm-smmu.h b/drivers/iommu/arm-smmu.h
index d172c024be61..f4c8bd7d0b34 100644
--- a/drivers/iommu/arm-smmu.h
+++ b/drivers/iommu/arm-smmu.h
@@ -382,6 +382,7 @@ struct arm_smmu_impl {
 	void (*write_reg64)(struct arm_smmu_device *smmu, int page, int offset,
 			    u64 val);
 	int (*cfg_probe)(struct arm_smmu_device *smmu);
+	u32 (*cfg_id2_fixup)(u32 id);
 	int (*reset)(struct arm_smmu_device *smmu);
 	int (*init_context)(struct arm_smmu_domain *smmu_domain);
 	void (*tlb_sync)(struct arm_smmu_device *smmu, int page, int sync,
-- 
2.17.1