linux-kernel - [PATCH 1/1] iommu/arm-smmu: Implement qcom,skip-init

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Message-Id: <20200704122809.73794-1-konradybcio@gmail.com>
Date:   Sat,  4 Jul 2020 14:28:09 +0200
From:   Konrad Dybcio <konradybcio@...il.com>
To:     skrzynka@...radybcio.pl
Cc:     Konrad Dybcio <konradybcio@...il.com>,
        Will Deacon <will@...nel.org>,
        Robin Murphy <robin.murphy@....com>,
        Joerg Roedel <joro@...tes.org>,
        Rob Herring <robh+dt@...nel.org>,
        linux-arm-kernel@...ts.infradead.org,
        iommu@...ts.linux-foundation.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH 1/1] iommu/arm-smmu: Implement qcom,skip-init

This adds the downstream property required to support
SMMUs on SDM630 and other platforms (the need for it
most likely depends on firmware configuration).

Signed-off-by: Konrad Dybcio <konradybcio@...il.com>
---
 .../devicetree/bindings/iommu/arm,smmu.yaml       | 10 ++++++++++
 drivers/iommu/arm-smmu.c                          | 15 +++++++++------
 2 files changed, 19 insertions(+), 6 deletions(-)

diff --git a/Documentation/devicetree/bindings/iommu/arm,smmu.yaml b/Documentation/devicetree/bindings/iommu/arm,smmu.yaml
index d7ceb4c34423..9abd6d41a32c 100644
--- a/Documentation/devicetree/bindings/iommu/arm,smmu.yaml
+++ b/Documentation/devicetree/bindings/iommu/arm,smmu.yaml
@@ -102,6 +102,16 @@ properties:
       access to SMMU configuration registers. In this case non-secure aliases of
       secure registers have to be used during SMMU configuration.
 
+  qcom,skip-init:
+    description: |
+      Disable resetting configuration for all context banks
+      during device reset.  This is useful for targets where
+      some context banks are dedicated to other execution
+      environments outside of Linux and those other EEs are
+      programming their own stream match tables, SCTLR, etc.
+      Without setting this option we will trample on their
+      configuration.
+
   stream-match-mask:
     $ref: /schemas/types.yaml#/definitions/uint32
     description: |
diff --git a/drivers/iommu/arm-smmu.c b/drivers/iommu/arm-smmu.c
index 243bc4cb2705..a5c623d4caf9 100644
--- a/drivers/iommu/arm-smmu.c
+++ b/drivers/iommu/arm-smmu.c
@@ -1655,13 +1655,16 @@ static void arm_smmu_device_reset(struct arm_smmu_device *smmu)
 	 * Reset stream mapping groups: Initial values mark all SMRn as
 	 * invalid and all S2CRn as bypass unless overridden.
 	 */
-	for (i = 0; i < smmu->num_mapping_groups; ++i)
-		arm_smmu_write_sme(smmu, i);
 
-	/* Make sure all context banks are disabled and clear CB_FSR  */
-	for (i = 0; i < smmu->num_context_banks; ++i) {
-		arm_smmu_write_context_bank(smmu, i);
-		arm_smmu_cb_write(smmu, i, ARM_SMMU_CB_FSR, ARM_SMMU_FSR_FAULT);
+	if (!of_find_property(smmu->dev->of_node, "qcom,skip-init", NULL)) {
+		for (i = 0; i < smmu->num_mapping_groups; ++i)
+			arm_smmu_write_sme(smmu, i);
+
+		/* Make sure all context banks are disabled and clear CB_FSR  */
+		for (i = 0; i < smmu->num_context_banks; ++i) {
+			arm_smmu_write_context_bank(smmu, i);
+			arm_smmu_cb_write(smmu, i, ARM_SMMU_CB_FSR, ARM_SMMU_FSR_FAULT);
+		}
 	}
 
 	/* Invalidate the TLB, just in case */
-- 
2.27.0