[RFC 09/13] iommu/arm-smmu: Make use of dev_64bit_mmio_supported()

[Nicolas Saenz Julienne]

Some arm SMMU implementations might sit on a bus that doesn't support
64bit memory accesses. In that case default to using hi_lo_{readq,
writeq}() and BUG if such platform tries to use AArch64 formats as they
rely on writeq()'s atomicity.

Signed-off-by: Nicolas Saenz Julienne <nsaenzjulienne@xxxxxxx>
---
 drivers/iommu/arm/arm-smmu/arm-smmu.c | 9 +++++++++
 drivers/iommu/arm/arm-smmu/arm-smmu.h | 9 +++++++--
 2 files changed, 16 insertions(+), 2 deletions(-)

diff --git a/drivers/iommu/arm/arm-smmu/arm-smmu.c b/drivers/iommu/arm/arm-smmu/arm-smmu.c
index d8c6bfde6a61..239ff42b20c3 100644
--- a/drivers/iommu/arm/arm-smmu/arm-smmu.c
+++ b/drivers/iommu/arm/arm-smmu/arm-smmu.c
@@ -1889,6 +1889,15 @@ static int arm_smmu_device_cfg_probe(struct arm_smmu_device *smmu)
 			smmu->features |= ARM_SMMU_FEAT_FMT_AARCH64_64K;
 	}
 
+	/*
+	 * 64bit accesses not possible through the interconnect, AArch64
+	 * formats depend on it.
+	 */
+	BUG_ON(!dev_64bit_mmio_supported(smmu->dev) &&
+	       smmu->features & (ARM_SMMU_FEAT_FMT_AARCH64_4K |
+				ARM_SMMU_FEAT_FMT_AARCH64_16K |
+				ARM_SMMU_FEAT_FMT_AARCH64_64K));
+
 	if (smmu->impl && smmu->impl->cfg_probe) {
 		ret = smmu->impl->cfg_probe(smmu);
 		if (ret)
diff --git a/drivers/iommu/arm/arm-smmu/arm-smmu.h b/drivers/iommu/arm/arm-smmu/arm-smmu.h
index d2a2d1bc58ba..997d13a21717 100644
--- a/drivers/iommu/arm/arm-smmu/arm-smmu.h
+++ b/drivers/iommu/arm/arm-smmu/arm-smmu.h
@@ -477,15 +477,20 @@ static inline void arm_smmu_writel(struct arm_smmu_device *smmu, int page,
 {
 	if (smmu->impl && unlikely(smmu->impl->write_reg))
 		smmu->impl->write_reg(smmu, page, offset, val);
-	else
+	else if (dev_64bit_mmio_supported(smmu->dev))
 		writel_relaxed(val, arm_smmu_page(smmu, page) + offset);
+	else
+		hi_lo_writeq_relaxed(val, arm_smmu_page(smmu, page) + offset);
 }
 
 static inline u64 arm_smmu_readq(struct arm_smmu_device *smmu, int page, int offset)
 {
 	if (smmu->impl && unlikely(smmu->impl->read_reg64))
 		return smmu->impl->read_reg64(smmu, page, offset);
-	return readq_relaxed(arm_smmu_page(smmu, page) + offset);
+	else if (dev_64bit_mmio_supported(smmu->dev))
+		return readq_relaxed(arm_smmu_page(smmu, page) + offset);
+	else
+		return hi_lo_readq_relaxed(arm_smmu_page(smmu, page) + offset);
 }
 
 static inline void arm_smmu_writeq(struct arm_smmu_device *smmu, int page,
-- 
2.30.1