[PATCH 5/5] iommu/arm-smmu: Setup identity domain for boot mappings

[Bjorn Andersson <bjorn.andersson@linaro.org>]

With many Qualcomm platforms not having functional S2CR BYPASS a
temporary IOMMU domain, without translation, needs to be allocated in
order to allow these memory transactions.

Unfortunately the boot loader uses the first few context banks, so
rather than overwriting a active bank the last context bank is used and
streams are diverted here during initialization.

This also performs the readback of SMR registers for the Qualcomm
platform, to trigger the mechanism.

This is based on prior work by Thierry Reding and Laurentiu Tudor.

Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
---
 drivers/iommu/arm-smmu-qcom.c | 11 +++++
 drivers/iommu/arm-smmu.c      | 80 +++++++++++++++++++++++++++++++++--
 drivers/iommu/arm-smmu.h      |  3 ++
 3 files changed, 90 insertions(+), 4 deletions(-)

diff --git a/drivers/iommu/arm-smmu-qcom.c b/drivers/iommu/arm-smmu-qcom.c
index 86b1917459a4..397df27c1d69 100644
--- a/drivers/iommu/arm-smmu-qcom.c
+++ b/drivers/iommu/arm-smmu-qcom.c
@@ -26,6 +26,7 @@ static const struct of_device_id qcom_smmu_client_of_match[] = {
 static int qcom_smmu_cfg_probe(struct arm_smmu_device *smmu)
 {
 	unsigned int last_s2cr = ARM_SMMU_GR0_S2CR(smmu->num_mapping_groups - 1);
+	u32 smr;
 	u32 reg;
 	int i;
 
@@ -56,6 +57,16 @@ static int qcom_smmu_cfg_probe(struct arm_smmu_device *smmu)
 		}
 	}
 
+	for (i = 0; i < smmu->num_mapping_groups; i++) {
+		smr = arm_smmu_gr0_read(smmu, ARM_SMMU_GR0_SMR(i));
+
+		if (FIELD_GET(ARM_SMMU_SMR_VALID, smr)) {
+			smmu->smrs[i].id = FIELD_GET(ARM_SMMU_SMR_ID, smr);
+			smmu->smrs[i].mask = FIELD_GET(ARM_SMMU_SMR_MASK, smr);
+			smmu->smrs[i].valid = true;
+		}
+	}
+
 	return 0;
 }
 
diff --git a/drivers/iommu/arm-smmu.c b/drivers/iommu/arm-smmu.c
index e2d6c0aaf1ea..a7cb27c1a49e 100644
--- a/drivers/iommu/arm-smmu.c
+++ b/drivers/iommu/arm-smmu.c
@@ -652,7 +652,8 @@ static void arm_smmu_write_context_bank(struct arm_smmu_device *smmu, int idx)
 }
 
 static int arm_smmu_init_domain_context(struct iommu_domain *domain,
-					struct arm_smmu_device *smmu)
+					struct arm_smmu_device *smmu,
+					bool boot_domain)
 {
 	int irq, start, ret = 0;
 	unsigned long ias, oas;
@@ -770,6 +771,15 @@ static int arm_smmu_init_domain_context(struct iommu_domain *domain,
 		ret = -EINVAL;
 		goto out_unlock;
 	}
+
+	/*
+	 * Use the last context bank for identity mappings during boot, to
+	 * avoid overwriting in-use bank configuration while we're setting up
+	 * the new mappings.
+	 */
+	if (boot_domain)
+		start = smmu->num_context_banks - 1;
+
 	ret = __arm_smmu_alloc_bitmap(smmu->context_map, start,
 				      smmu->num_context_banks);
 	if (ret < 0)
@@ -1149,7 +1159,10 @@ static int arm_smmu_attach_dev(struct iommu_domain *domain, struct device *dev)
 	struct iommu_fwspec *fwspec = dev_iommu_fwspec_get(dev);
 	struct arm_smmu_master_cfg *cfg;
 	struct arm_smmu_device *smmu;
+	bool free_identity_domain = false;
+	int idx;
 	int ret;
+	int i;
 
 	if (!fwspec || fwspec->ops != &arm_smmu_ops) {
 		dev_err(dev, "cannot attach to SMMU, is it on the same bus?\n");
@@ -1174,7 +1187,7 @@ static int arm_smmu_attach_dev(struct iommu_domain *domain, struct device *dev)
 		return ret;
 
 	/* Ensure that the domain is finalised */
-	ret = arm_smmu_init_domain_context(domain, smmu);
+	ret = arm_smmu_init_domain_context(domain, smmu, false);
 	if (ret < 0)
 		goto rpm_put;
 
@@ -1190,9 +1203,34 @@ static int arm_smmu_attach_dev(struct iommu_domain *domain, struct device *dev)
 		goto rpm_put;
 	}
 
+	/* Decrement use counter for any references to the identity domain */
+	mutex_lock(&smmu->stream_map_mutex);
+	if (smmu->identity) {
+		struct arm_smmu_domain *identity = to_smmu_domain(smmu->identity);
+
+		for_each_cfg_sme(cfg, fwspec, i, idx) {
+			dev_err(smmu->dev, "%s() %#x\n", __func__, smmu->smrs[idx].id);
+			if (smmu->s2crs[idx].cbndx == identity->cfg.cbndx) {
+				smmu->num_identity_masters--;
+				if (smmu->num_identity_masters == 0)
+					free_identity_domain = true;
+			}
+		}
+	}
+	mutex_unlock(&smmu->stream_map_mutex);
+
 	/* Looks ok, so add the device to the domain */
 	ret = arm_smmu_domain_add_master(smmu_domain, cfg, fwspec);
 
+	/*
+	 * The last stream map to reference the identity domain has been
+	 * overwritten, so it's now okay to free it.
+	 */
+	if (free_identity_domain) {
+		arm_smmu_domain_free(smmu->identity);
+		smmu->identity = NULL;
+	}
+
 	/*
 	 * Setup an autosuspend delay to avoid bouncing runpm state.
 	 * Otherwise, if a driver for a suspended consumer device
@@ -1922,17 +1960,51 @@ static int arm_smmu_device_cfg_probe(struct arm_smmu_device *smmu)
 
 int arm_smmu_setup_identity(struct arm_smmu_device *smmu)
 {
+	struct device *dev = smmu->dev;
+	int cbndx = 0xff;
+	int type = S2CR_TYPE_BYPASS;
+	int ret;
 	int i;
 
+	if (smmu->qcom_bypass_quirk) {
+		/* Create a IDENTITY domain to use for all inherited streams */
+		smmu->identity = arm_smmu_domain_alloc(IOMMU_DOMAIN_IDENTITY);
+		if (!smmu->identity) {
+			dev_err(dev, "failed to create identity domain\n");
+			return -ENOMEM;
+		}
+
+		smmu->identity->pgsize_bitmap = smmu->pgsize_bitmap;
+		smmu->identity->type = IOMMU_DOMAIN_IDENTITY;
+		smmu->identity->ops = &arm_smmu_ops;
+
+		ret = arm_smmu_init_domain_context(smmu->identity, smmu, true);
+		if (ret < 0) {
+			dev_err(dev, "failed to initialize identity domain: %d\n", ret);
+			return ret;
+		}
+
+		type = S2CR_TYPE_TRANS;
+		cbndx = to_smmu_domain(smmu->identity)->cfg.cbndx;
+	}
+
 	for (i = 0; i < smmu->num_mapping_groups; i++) {
 		if (smmu->smrs[i].valid) {
-			smmu->s2crs[i].type = S2CR_TYPE_BYPASS;
+			smmu->s2crs[i].type = type;
 			smmu->s2crs[i].privcfg = S2CR_PRIVCFG_DEFAULT;
-			smmu->s2crs[i].cbndx = 0xff;
+			smmu->s2crs[i].cbndx = cbndx;
 			smmu->s2crs[i].count++;
+
+			smmu->num_identity_masters++;
 		}
 	}
 
+	/* If no mappings where found, free the identiy domain again */
+	if (smmu->identity && !smmu->num_identity_masters) {
+		arm_smmu_domain_free(smmu->identity);
+		smmu->identity = NULL;
+	}
+
 	return 0;
 }
 
diff --git a/drivers/iommu/arm-smmu.h b/drivers/iommu/arm-smmu.h
index bcd160d01c53..37257ede86fa 100644
--- a/drivers/iommu/arm-smmu.h
+++ b/drivers/iommu/arm-smmu.h
@@ -321,6 +321,9 @@ struct arm_smmu_device {
 	/* IOMMU core code handle */
 	struct iommu_device		iommu;
 
+	struct iommu_domain		*identity;
+	unsigned int			num_identity_masters;
+
 	bool				qcom_bypass_quirk;
 };
 
-- 
2.26.2