linux-kernel - [PATCH 2/2] iommu/arm-smmu: Add support for non-coherent page table mappings

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Message-Id: <20190117092718.1396-3-vivek.gautam@codeaurora.org>
Date:   Thu, 17 Jan 2019 14:57:18 +0530
From:   Vivek Gautam <vivek.gautam@...eaurora.org>
To:     will.deacon@....com, robin.murphy@....com, joro@...tes.org,
        iommu@...ts.linux-foundation.org
Cc:     linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-arm-msm@...r.kernel.org, tfiga@...omium.org,
        Vivek Gautam <vivek.gautam@...eaurora.org>
Subject: [PATCH 2/2] iommu/arm-smmu: Add support for non-coherent page table mappings

Adding a device tree option for arm smmu to enable non-cacheable
memory for page tables.
We already enable a smmu feature for coherent walk based on
whether the smmu device is dma-coherent or not. Have an option
to enable non-cacheable page table memory to force set it for
particular smmu devices.

Signed-off-by: Vivek Gautam <vivek.gautam@...eaurora.org>
---
 drivers/iommu/arm-smmu.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/iommu/arm-smmu.c b/drivers/iommu/arm-smmu.c
index af18a7e7f917..7ebbcf1b2eb3 100644
--- a/drivers/iommu/arm-smmu.c
+++ b/drivers/iommu/arm-smmu.c
@@ -188,6 +188,7 @@ struct arm_smmu_device {
 	u32				features;
 
 #define ARM_SMMU_OPT_SECURE_CFG_ACCESS (1 << 0)
+#define ARM_SMMU_OPT_PGTBL_NON_COHERENT (1 << 1)
 	u32				options;
 	enum arm_smmu_arch_version	version;
 	enum arm_smmu_implementation	model;
@@ -273,6 +274,7 @@ static bool using_legacy_binding, using_generic_binding;
 
 static struct arm_smmu_option_prop arm_smmu_options[] = {
 	{ ARM_SMMU_OPT_SECURE_CFG_ACCESS, "calxeda,smmu-secure-config-access" },
+	{ ARM_SMMU_OPT_PGTBL_NON_COHERENT, "arm,smmu-pgtable-non-coherent" },
 	{ 0, NULL},
 };
 
@@ -902,6 +904,11 @@ static int arm_smmu_init_domain_context(struct iommu_domain *domain,
 	if (smmu_domain->non_strict)
 		pgtbl_cfg.quirks |= IO_PGTABLE_QUIRK_NON_STRICT;
 
+	/* Non coherent page table mappings only for Stage-1 */
+	if (smmu->options & ARM_SMMU_OPT_PGTBL_NON_COHERENT &&
+	    smmu_domain->stage == ARM_SMMU_DOMAIN_S1)
+		pgtbl_cfg.quirks |= IO_PGTABLE_QUIRK_NON_COHERENT;
+
 	smmu_domain->smmu = smmu;
 	pgtbl_ops = alloc_io_pgtable_ops(fmt, &pgtbl_cfg, smmu_domain);
 	if (!pgtbl_ops) {
-- 
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