linux-kernel - [PATCH v14 1/6] iommu/arm-smmu: re-enable context caching in smmu reset operation

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Message-ID: <20240816174259.2056829-2-quic_bibekkum@quicinc.com>
Date: Fri, 16 Aug 2024 23:12:54 +0530
From: Bibek Kumar Patro <quic_bibekkum@...cinc.com>
To: <robdclark@...il.com>, <will@...nel.org>, <robin.murphy@....com>,
        <joro@...tes.org>, <jgg@...pe.ca>, <jsnitsel@...hat.com>,
        <robh@...nel.org>, <krzysztof.kozlowski@...aro.org>,
        <quic_c_gdjako@...cinc.com>, <dmitry.baryshkov@...aro.org>,
        <konrad.dybcio@...aro.org>
CC: <iommu@...ts.linux.dev>, <linux-arm-msm@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>, <linux-kernel@...r.kernel.org>,
        "Bibek Kumar Patro" <quic_bibekkum@...cinc.com>
Subject: [PATCH v14 1/6] iommu/arm-smmu: re-enable context caching in smmu reset operation

Default MMU-500 reset operation disables context caching in
prefetch buffer. It is however expected for context banks using
the ACTLR register to retain their prefetch value during reset
and runtime suspend.

Replace default MMU-500 reset operation with Qualcomm specific reset
operation which envelope the default reset operation and re-enables
context caching in prefetch buffer for Qualcomm SoCs.

Reviewed-by: Konrad Dybcio <konrad.dybcio@...aro.org>
Signed-off-by: Bibek Kumar Patro <quic_bibekkum@...cinc.com>
---
 drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c | 36 ++++++++++++++++++++--
 1 file changed, 33 insertions(+), 3 deletions(-)

diff --git a/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c b/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c
index 36c6b36ad4ff..8ac1850b852f 100644
--- a/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c
+++ b/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c
@@ -16,6 +16,16 @@

 #define QCOM_DUMMY_VAL	-1

+/*
+ * SMMU-500 TRM defines BIT(0) as CMTLB (Enable context caching in the
+ * macro TLB) and BIT(1) as CPRE (Enable context caching in the prefetch
+ * buffer). The remaining bits are implementation defined and vary across
+ * SoCs.
+ */
+
+#define CPRE			(1 << 1)
+#define CMTLB			(1 << 0)
+
 static struct qcom_smmu *to_qcom_smmu(struct arm_smmu_device *smmu)
 {
 	return container_of(smmu, struct qcom_smmu, smmu);
@@ -381,11 +391,31 @@ static int qcom_smmu_def_domain_type(struct device *dev)
 	return match ? IOMMU_DOMAIN_IDENTITY : 0;
 }

+static int qcom_smmu500_reset(struct arm_smmu_device *smmu)
+{
+	int ret;
+	u32 val;
+	int i;
+
+	ret = arm_mmu500_reset(smmu);
+	if (ret)
+		return ret;
+
+	/* arm_mmu500_reset() disables CPRE which is re-enabled here */
+	for (i = 0; i < smmu->num_context_banks; ++i) {
+		val = arm_smmu_cb_read(smmu, i, ARM_SMMU_CB_ACTLR);
+		val |= CPRE;
+		arm_smmu_cb_write(smmu, i, ARM_SMMU_CB_ACTLR, val);
+	}
+
+	return 0;
+}
+
 static int qcom_sdm845_smmu500_reset(struct arm_smmu_device *smmu)
 {
 	int ret;

-	arm_mmu500_reset(smmu);
+	qcom_smmu500_reset(smmu);

 	/*
 	 * To address performance degradation in non-real time clients,
@@ -412,7 +442,7 @@ static const struct arm_smmu_impl qcom_smmu_500_impl = {
 	.init_context = qcom_smmu_init_context,
 	.cfg_probe = qcom_smmu_cfg_probe,
 	.def_domain_type = qcom_smmu_def_domain_type,
-	.reset = arm_mmu500_reset,
+	.reset = qcom_smmu500_reset,
 	.write_s2cr = qcom_smmu_write_s2cr,
 	.tlb_sync = qcom_smmu_tlb_sync,
 #ifdef CONFIG_ARM_SMMU_QCOM_DEBUG
@@ -445,7 +475,7 @@ static const struct arm_smmu_impl qcom_adreno_smmu_v2_impl = {
 static const struct arm_smmu_impl qcom_adreno_smmu_500_impl = {
 	.init_context = qcom_adreno_smmu_init_context,
 	.def_domain_type = qcom_smmu_def_domain_type,
-	.reset = arm_mmu500_reset,
+	.reset = qcom_smmu500_reset,
 	.alloc_context_bank = qcom_adreno_smmu_alloc_context_bank,
 	.write_sctlr = qcom_adreno_smmu_write_sctlr,
 	.tlb_sync = qcom_smmu_tlb_sync,
--
2.34.1