[RFC 2/2] iommu: arm-smmu: Don't blindly use first SMR to calculate mask

Bjorn Andersson
2019-06-05T21:09:14Z

With the SMRs inherited from the bootloader the first SMR might actually
be valid and in use. As such probing the SMR mask using the first SMR
might break a stream in use. Search for an unused stream and use this to
probe the SMR mask.

Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
---
drivers/iommu/arm-smmu.c | 20 ++++++++++++++++----
1 file changed, 16 insertions(+), 4 deletions(-)

diff --git a/drivers/iommu/arm-smmu.c b/drivers/iommu/arm-smmu.c
index c8629a656b42..0c6f5fe6f382 100644
--- a/drivers/iommu/arm-smmu.c
+++ b/drivers/iommu/arm-smmu.c
@@ -1084,23 +1084,35 @@ static void arm_smmu_test_smr_masks(struct arm_smmu_device *smmu)
{
void __iomem *gr0_base = ARM_SMMU_GR0(smmu);
u32 smr;
+ int idx;

if (!smmu->smrs)
return;

+ for (idx = 0; idx < smmu->num_mapping_groups; idx++) {
+ smr = readl_relaxed(gr0_base + ARM_SMMU_GR0_SMR(idx));
+ if (!(smr & SMR_VALID))
+ break;
+ }
+
+ if (idx == smmu->num_mapping_groups) {
+ dev_err(smmu->dev, "Unable to compute streamid_mask\n");
+ return;
+ }
+
/*
* SMR.ID bits may not be preserved if the corresponding MASK
* bits are set, so check each one separately. We can reject
* masters later if they try to claim IDs outside these masks.
*/
smr = smmu->streamid_mask << SMR_ID_SHIFT;
- writel_relaxed(smr, gr0_base + ARM_SMMU_GR0_SMR(0));
- smr = readl_relaxed(gr0_base + ARM_SMMU_GR0_SMR(0));
+ writel_relaxed(smr, gr0_base + ARM_SMMU_GR0_SMR(idx));
+ smr = readl_relaxed(gr0_base + ARM_SMMU_GR0_SMR(idx));
smmu->streamid_mask = smr >> SMR_ID_SHIFT;

smr = smmu->streamid_mask << SMR_MASK_SHIFT;
- writel_relaxed(smr, gr0_base + ARM_SMMU_GR0_SMR(0));
- smr = readl_relaxed(gr0_base + ARM_SMMU_GR0_SMR(0));
+ writel_relaxed(smr, gr0_base + ARM_SMMU_GR0_SMR(idx));
+ smr = readl_relaxed(gr0_base + ARM_SMMU_GR0_SMR(idx));
smmu->smr_mask_mask = smr >> SMR_MASK_SHIFT;
}

--
2.18.0