[RFC 1/2] iommu: arm-smmu: Handoff SMR registers and context banks

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

Boot splash screen or EFI framebuffer requires the display hardware to
operate while the Linux iommu driver probes. Therefore, we cannot simply
wipe out the SMR register settings programmed by the bootloader.

Detect which SMR registers are in use during probe, and which context
banks they are associated with. Reserve these context banks for the
first Linux device whose stream-id matches the SMR register.

Any existing page-tables will be discarded.

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

Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
---
 drivers/iommu/arm-smmu-regs.h |  2 +
 drivers/iommu/arm-smmu.c      | 80 ++++++++++++++++++++++++++++++++---
 2 files changed, 77 insertions(+), 5 deletions(-)

diff --git a/drivers/iommu/arm-smmu-regs.h b/drivers/iommu/arm-smmu-regs.h
index e9132a926761..8c1fd84032a2 100644
--- a/drivers/iommu/arm-smmu-regs.h
+++ b/drivers/iommu/arm-smmu-regs.h
@@ -105,7 +105,9 @@
 #define ARM_SMMU_GR0_SMR(n)		(0x800 + ((n) << 2))
 #define SMR_VALID			(1 << 31)
 #define SMR_MASK_SHIFT			16
+#define SMR_MASK_MASK			0x7fff
 #define SMR_ID_SHIFT			0
+#define SMR_ID_MASK			0xffff
 
 #define ARM_SMMU_GR0_S2CR(n)		(0xc00 + ((n) << 2))
 #define S2CR_CBNDX_SHIFT		0
diff --git a/drivers/iommu/arm-smmu.c b/drivers/iommu/arm-smmu.c
index 5e54cc0a28b3..c8629a656b42 100644
--- a/drivers/iommu/arm-smmu.c
+++ b/drivers/iommu/arm-smmu.c
@@ -135,6 +135,7 @@ struct arm_smmu_s2cr {
 	enum arm_smmu_s2cr_type		type;
 	enum arm_smmu_s2cr_privcfg	privcfg;
 	u8				cbndx;
+	bool				handoff;
 };
 
 #define s2cr_init_val (struct arm_smmu_s2cr){				\
@@ -399,9 +400,22 @@ 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 cbndx;
 	int idx;
+	int i;
+
+	for_each_cfg_sme(fwspec, i, idx) {
+		if (smmu->s2crs[idx].handoff) {
+			cbndx = smmu->s2crs[idx].cbndx;
+			goto found_handoff;
+		}
+	}
 
 	do {
 		idx = find_next_zero_bit(map, end, start);
@@ -410,6 +424,17 @@ static int __arm_smmu_alloc_bitmap(unsigned long *map, int start, int end)
 	} while (test_and_set_bit(idx, map));
 
 	return idx;
+
+found_handoff:
+	for (i = 0; i < smmu->num_mapping_groups; i++) {
+		if (smmu->s2crs[i].cbndx == cbndx) {
+			smmu->s2crs[i].cbndx = 0;
+			smmu->s2crs[i].handoff = false;
+			smmu->s2crs[i].count--;
+		}
+	}
+
+	return cbndx;
 }
 
 static void __arm_smmu_free_bitmap(unsigned long *map, int idx)
@@ -759,7 +784,8 @@ 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;
@@ -873,8 +899,7 @@ 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;
 
@@ -1264,7 +1289,7 @@ 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;
 
@@ -1798,6 +1823,49 @@ static void arm_smmu_device_reset(struct arm_smmu_device *smmu)
 	writel(reg, ARM_SMMU_GR0_NS(smmu) + ARM_SMMU_GR0_sCR0);
 }
 
+static void arm_smmu_read_smr_state(struct arm_smmu_device *smmu)
+{
+	u32 privcfg;
+	u32 cbndx;
+	u32 mask;
+	u32 type;
+	u32 s2cr;
+	u32 smr;
+	u32 id;
+	int i;
+
+	for (i = 0; i < smmu->num_mapping_groups; i++) {
+		smr = readl_relaxed(ARM_SMMU_GR0(smmu) + ARM_SMMU_GR0_SMR(i));
+		mask = (smr >> SMR_MASK_SHIFT) & SMR_MASK_MASK;
+		id = smr & SMR_ID_MASK;
+		if (!(smr & SMR_VALID))
+			continue;
+
+		s2cr = readl_relaxed(ARM_SMMU_GR0(smmu) + ARM_SMMU_GR0_S2CR(i));
+		type = (s2cr >> S2CR_TYPE_SHIFT) & S2CR_TYPE_MASK;
+		cbndx = (s2cr >> S2CR_CBNDX_SHIFT) & S2CR_CBNDX_MASK;
+		privcfg = (s2cr >> S2CR_PRIVCFG_SHIFT) & S2CR_PRIVCFG_MASK;
+		if (type != S2CR_TYPE_TRANS)
+			continue;
+
+		/* Populate the SMR */
+		smmu->smrs[i].mask = mask;
+		smmu->smrs[i].id = id;
+		smmu->smrs[i].valid = true;
+
+		/* Populate the S2CR */
+		smmu->s2crs[i].group = NULL;
+		smmu->s2crs[i].count = 1;
+		smmu->s2crs[i].type = type;
+		smmu->s2crs[i].privcfg = privcfg;
+		smmu->s2crs[i].cbndx = cbndx;
+		smmu->s2crs[i].handoff = true;
+
+		/* Mark the context bank as busy */
+		bitmap_set(smmu->context_map, cbndx, 1);
+	}
+}
+
 static int arm_smmu_id_size_to_bits(int size)
 {
 	switch (size) {
@@ -2023,6 +2091,8 @@ static int arm_smmu_device_cfg_probe(struct arm_smmu_device *smmu)
 		dev_notice(smmu->dev, "\tStage-2: %lu-bit IPA -> %lu-bit PA\n",
 			   smmu->ipa_size, smmu->pa_size);
 
+	arm_smmu_read_smr_state(smmu);
+
 	return 0;
 }
 
-- 
2.18.0

_______________________________________________
iommu mailing list
iommu@lists.linux-foundation.org
https://lists.linuxfoundation.org/mailman/listinfo/iommu