iommu/arm-smmu-qcom: Avoid disabling secured context banks

Some Qualcomm SoCs' TZ/hypervisor configuration is disallowing the
disablement of some context banks, being them used for tzapps and/or
remote processors; any attempt to disable such CBs will result in
triggering a fault and the system will freeze and/or reset.

For this reason, get a list of context banks that should never get
disabled during smmu initialization through a DT array property
`qcom,reset-nodisable-cbs`.
It was chosen to not hardcode the CBs as this is dependant on the
SoC's firmware, which may vary on different boards.

Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@somainline.org>
(JAMI: fixup for v6.0-rc1)

drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c

@@ -397,10 +397,32 @@ static int qcom_sdm845_smmu500_reset(struct arm_smmu_device *smmu)
 	return ret;
 }
 
+static int qcom_smmu500_reset(struct arm_smmu_device *smmu)
+{
+	const struct device_node *np = smmu->dev->of_node;
+
+	arm_mmu500_reset(smmu);
+
+	if (of_device_is_compatible(np, "qcom,sdm845-smmu-500"))
+		return qcom_sdm845_smmu500_reset(smmu);
+
+	return 0;
+}
+
+static bool qcom_smmu500_reset_cb_nodisable(struct arm_smmu_device *smmu,
+					    int cbndx)
+{
+	struct qcom_smmu *qsmmu = to_qcom_smmu(smmu);
+
+	return test_bit(cbndx, qsmmu->reset_cb_nodisable_mask);
+}
+
 static const struct arm_smmu_impl qcom_smmu_v2_impl = {
 	.init_context = qcom_smmu_init_context,
 	.cfg_probe = qcom_smmu_cfg_probe,
 	.def_domain_type = qcom_smmu_def_domain_type,
+	.reset = qcom_smmu500_reset,
+	.reset_cb_nodisable = qcom_smmu500_reset_cb_nodisable,
 	.write_s2cr = qcom_smmu_write_s2cr,
 	.tlb_sync = qcom_smmu_tlb_sync,
 };
@@ -426,6 +448,8 @@ static const struct arm_smmu_impl sdm845_smmu_500_impl = {
 static const struct arm_smmu_impl qcom_adreno_smmu_v2_impl = {
 	.init_context = qcom_adreno_smmu_init_context,
 	.def_domain_type = qcom_smmu_def_domain_type,
+	.reset = qcom_smmu500_reset,
+	.reset_cb_nodisable = qcom_smmu500_reset_cb_nodisable,
 	.alloc_context_bank = qcom_adreno_smmu_alloc_context_bank,
 	.write_sctlr = qcom_adreno_smmu_write_sctlr,
 	.tlb_sync = qcom_smmu_tlb_sync,
@@ -446,6 +470,8 @@ static struct arm_smmu_device *qcom_smmu_create(struct arm_smmu_device *smmu,
 	const struct device_node *np = smmu->dev->of_node;
 	const struct arm_smmu_impl *impl;
 	struct qcom_smmu *qsmmu;
+	u8 reset_nodisable_cbs[ARM_SMMU_MAX_CBS];
+	int i, sz;
 
 	if (!data)
 		return ERR_PTR(-EINVAL);
@@ -469,6 +495,7 @@ static struct arm_smmu_device *qcom_smmu_create(struct arm_smmu_device *smmu,
 	qsmmu->smmu.impl = impl;
 	qsmmu->cfg = data->cfg;
 	qsmmu->bypass_cbndx = 0xff;
+	bitmap_zero(qsmmu->reset_cb_nodisable_mask, ARM_SMMU_MAX_CBS);
 
 	if (np != NULL) {
 		/*
@@ -477,6 +504,23 @@ static struct arm_smmu_device *qcom_smmu_create(struct arm_smmu_device *smmu,
 		 * - We are booting on ACPI
 		 */
 		of_property_read_u8(np, "qcom,bypass-cbndx", &qsmmu->bypass_cbndx);
+
+		/*
+		 * Some context banks may not be disabled because they are
+		 * secured: read from DT a list of secured contexts that cannot
+		 * be disabled without crashing the system.
+		 * This list is optional, as not all firmware configurations do
+		 * require us skipping disablement of context banks.
+		 */
+		sz = of_property_read_variable_u8_array(np, "qcom,reset-nodisable-cbs",
+							reset_nodisable_cbs,
+							1, ARM_SMMU_MAX_CBS);
+		if (sz > 0) {
+			for (i = 0; i < sz; i++) {
+				__set_bit(reset_nodisable_cbs[i],
+					  qsmmu->reset_cb_nodisable_mask);
+			}
+		}
 	}
 
 	return &qsmmu->smmu;

drivers/iommu/arm/arm-smmu/arm-smmu-qcom.h

@@ -9,6 +9,7 @@
 struct qcom_smmu {
 	struct arm_smmu_device smmu;
 	const struct qcom_smmu_config *cfg;
+	DECLARE_BITMAP(reset_cb_nodisable_mask, ARM_SMMU_MAX_CBS);
 	bool bypass_quirk;
 	u8 bypass_cbndx;
 	u32 stall_enabled;