[PATCH 3/3] iommu/arm-smmu: Allow inherting stream mapping from bootloader

[Bjorn Andersson]

The Qualcomm bootloaders leaves the IOMMU with stream mapping for
the display hardware to be able to read the framebuffer memory in DDR,
to continuously display a boot splash or to implement EFI framebuffer.

This patch implements support for implementations to pin stream mappings
and adds the code to the Qualcomm implementation for reading out the
stream mapping from the bootloader, with the result of maintaining the
display hardware's access to DDR until the context bank is enabled.

Heavily based on downstream implementation by Patrick Daly
<pdaly@xxxxxxxxxxxxxx>.

Signed-off-by: Bjorn Andersson <bjorn.andersson@xxxxxxxxxx>
---

Changes since RFC:
- Deal with EXIDS
- The onetime handoff has been replaced with a "pinned" state, to deal with
  probe deferring in the display driver
- Reads back s2cr for all groups, not only the "valid" ones

 drivers/iommu/arm-smmu-qcom.c | 35 +++++++++++++++++++++++++++++++++++
 drivers/iommu/arm-smmu.c      | 29 +++++++++++++++++++++++------
 drivers/iommu/arm-smmu.h      |  1 +
 3 files changed, 59 insertions(+), 6 deletions(-)

diff --git a/drivers/iommu/arm-smmu-qcom.c b/drivers/iommu/arm-smmu-qcom.c
index 24c071c1d8b0..06e5799dcb87 100644
--- a/drivers/iommu/arm-smmu-qcom.c
+++ b/drivers/iommu/arm-smmu-qcom.c
@@ -3,6 +3,7 @@
  * Copyright (c) 2019, The Linux Foundation. All rights reserved.
  */
 
+#include <linux/bitfield.h>
 #include <linux/qcom_scm.h>
 
 #include "arm-smmu.h"
@@ -11,6 +12,39 @@ struct qcom_smmu {
 	struct arm_smmu_device smmu;
 };
 
+static int qcom_sdm845_smmu500_cfg_probe(struct arm_smmu_device *smmu)
+{
+	u32 s2cr;
+	u32 smr;
+	int i;
+
+	for (i = 0; i < smmu->num_mapping_groups; i++) {
+		smr = arm_smmu_gr0_read(smmu, ARM_SMMU_GR0_SMR(i));
+		s2cr = arm_smmu_gr0_read(smmu, ARM_SMMU_GR0_S2CR(i));
+
+		smmu->smrs[i].mask = FIELD_GET(SMR_MASK, smr);
+		smmu->smrs[i].id = FIELD_GET(SMR_ID, smr);
+		if (smmu->features & ARM_SMMU_FEAT_EXIDS)
+			smmu->smrs[i].valid = FIELD_GET(S2CR_EXIDVALID, s2cr);
+		else
+			smmu->smrs[i].valid = FIELD_GET(SMR_VALID, smr);
+
+		smmu->s2crs[i].group = NULL;
+		smmu->s2crs[i].count = 0;
+		smmu->s2crs[i].type = FIELD_GET(S2CR_TYPE, s2cr);
+		smmu->s2crs[i].privcfg = FIELD_GET(S2CR_PRIVCFG, s2cr);
+		smmu->s2crs[i].cbndx = FIELD_GET(S2CR_CBNDX, s2cr);
+
+		if (!smmu->smrs[i].valid)
+			continue;
+
+		smmu->s2crs[i].pinned = true;
+		bitmap_set(smmu->context_map, smmu->s2crs[i].cbndx, 1);
+	}
+
+	return 0;
+}
+
 static int qcom_sdm845_smmu500_reset(struct arm_smmu_device *smmu)
 {
 	int ret;
@@ -31,6 +65,7 @@ static int qcom_sdm845_smmu500_reset(struct arm_smmu_device *smmu)
 }
 
 static const struct arm_smmu_impl qcom_smmu_impl = {
+	.cfg_probe = qcom_sdm845_smmu500_cfg_probe,
 	.reset = qcom_sdm845_smmu500_reset,
 };
 
diff --git a/drivers/iommu/arm-smmu.c b/drivers/iommu/arm-smmu.c
index 9a9091b9dcc7..01f22eff2ec5 100644
--- a/drivers/iommu/arm-smmu.c
+++ b/drivers/iommu/arm-smmu.c
@@ -206,9 +206,19 @@ static int arm_smmu_register_legacy_master(struct device *dev,
 	return err;
 }
 
-static int __arm_smmu_alloc_bitmap(unsigned long *map, int start, int end)
+static int __arm_smmu_alloc_cb(struct arm_smmu_device *smmu, int start,
+			       struct device *dev)
 {
+	struct iommu_fwspec *fwspec = dev_iommu_fwspec_get(dev);
+	unsigned long *map = smmu->context_map;
+	int end = smmu->num_context_banks;
 	int idx;
+	int i;
+
+	for_each_cfg_sme(fwspec, i, idx) {
+		if (smmu->s2crs[idx].pinned)
+			return smmu->s2crs[idx].cbndx;
+	}
 
 	do {
 		idx = find_next_zero_bit(map, end, start);
@@ -628,7 +638,8 @@ 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,
+					struct device *dev)
 {
 	int irq, start, ret = 0;
 	unsigned long ias, oas;
@@ -742,8 +753,7 @@ static int arm_smmu_init_domain_context(struct iommu_domain *domain,
 		ret = -EINVAL;
 		goto out_unlock;
 	}
-	ret = __arm_smmu_alloc_bitmap(smmu->context_map, start,
-				      smmu->num_context_banks);
+	ret = __arm_smmu_alloc_cb(smmu, start, dev);
 	if (ret < 0)
 		goto out_unlock;
 
@@ -1015,12 +1025,19 @@ static int arm_smmu_find_sme(struct arm_smmu_device *smmu, u16 id, u16 mask)
 
 static bool arm_smmu_free_sme(struct arm_smmu_device *smmu, int idx)
 {
+	bool pinned = smmu->s2crs[idx].pinned;
+	u8 cbndx = smmu->s2crs[idx].cbndx;;
+
 	if (--smmu->s2crs[idx].count)
 		return false;
 
 	smmu->s2crs[idx] = s2cr_init_val;
-	if (smmu->smrs)
+	if (pinned) {
+		smmu->s2crs[idx].pinned = true;
+		smmu->s2crs[idx].cbndx = cbndx;
+	} else if (smmu->smrs) {
 		smmu->smrs[idx].valid = false;
+	}
 
 	return true;
 }
@@ -1154,7 +1171,7 @@ 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, dev);
 	if (ret < 0)
 		goto rpm_put;
 
diff --git a/drivers/iommu/arm-smmu.h b/drivers/iommu/arm-smmu.h
index 73f94579b926..0701e6875964 100644
--- a/drivers/iommu/arm-smmu.h
+++ b/drivers/iommu/arm-smmu.h
@@ -230,6 +230,7 @@ struct arm_smmu_s2cr {
 	enum arm_smmu_s2cr_type		type;
 	enum arm_smmu_s2cr_privcfg	privcfg;
 	u8				cbndx;
+	bool				pinned;
 };
 
 struct arm_smmu_smr {
-- 
2.24.0