From: Manivannan Sadhasivam manivannan.sadhasivam@linaro.org
[ Upstream commit 12261134732689b7e30c59db9978f81230965181 ]
Some platforms support more than 128 stream matching groups than what is defined by the ARM SMMU architecture specification. But due to some unknown reasons, those additional groups don't exhibit the same behavior as the architecture supported ones.
For instance, the additional groups will not detect the quirky behavior of some firmware versions intercepting writes to S2CR register, thus skipping the quirk implemented in the driver and causing boot crash.
So let's limit the groups to 128 for now until the issue with those groups are fixed and issue a notice to users in that case.
Reviewed-by: Johan Hovold johan+linaro@kernel.org Tested-by: Johan Hovold johan+linaro@kernel.org Signed-off-by: Manivannan Sadhasivam manivannan.sadhasivam@linaro.org Link: https://lore.kernel.org/r/20230327080029.11584-1-manivannan.sadhasivam@linar... [will: Reworded the comment slightly] Signed-off-by: Will Deacon will@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c | 16 +++++++++++++++- 1 file changed, 15 insertions(+), 1 deletion(-)
diff --git a/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c b/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c index 63f7173b241f0..1598a1ddbf694 100644 --- a/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c +++ b/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c @@ -32,12 +32,26 @@ static const struct of_device_id qcom_smmu_client_of_match[] __maybe_unused = {
static int qcom_smmu_cfg_probe(struct arm_smmu_device *smmu) { - unsigned int last_s2cr = ARM_SMMU_GR0_S2CR(smmu->num_mapping_groups - 1); struct qcom_smmu *qsmmu = to_qcom_smmu(smmu); + unsigned int last_s2cr; u32 reg; u32 smr; int i;
+ /* + * Some platforms support more than the Arm SMMU architected maximum of + * 128 stream matching groups. For unknown reasons, the additional + * groups don't exhibit the same behavior as the architected registers, + * so limit the groups to 128 until the behavior is fixed for the other + * groups. + */ + if (smmu->num_mapping_groups > 128) { + dev_notice(smmu->dev, "\tLimiting the stream matching groups to 128\n"); + smmu->num_mapping_groups = 128; + } + + last_s2cr = ARM_SMMU_GR0_S2CR(smmu->num_mapping_groups - 1); + /* * With some firmware versions writes to S2CR of type FAULT are * ignored, and writing BYPASS will end up written as FAULT in the