Re: [PATCH 1/2] iommu/arm-smmu-qcom: Skip the TTBR1 quirk for db820c.

[Bjorn Andersson]

On Fri 26 Mar 18:13 CDT 2021, Eric Anholt wrote:

> db820c wants to use the qcom smmu path to get HUPCF set (which keeps
> the GPU from wedging and then sometimes wedging the kernel after a
> page fault), but it doesn't have separate pagetables support yet in
> drm/msm so we can't go all the way to the TTBR1 path.
> 
> Signed-off-by: Eric Anholt <eric@xxxxxxxxxx>

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

Regards,
Bjorn

> ---
> 
> We've been seeing a flaky test per day or so in Mesa CI where the
> kernel gets wedged after an iommu fault turns into CP errors.  With
> this patch, the CI isn't throwing the string of CP errors on the
> faults in any of the ~10 jobs I've run so far.
> 
>  drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c | 13 ++++++++++++-
>  1 file changed, 12 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 bcda17012aee..51f22193e456 100644
> --- a/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c
> +++ b/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c
> @@ -130,6 +130,16 @@ static int qcom_adreno_smmu_alloc_context_bank(struct arm_smmu_domain *smmu_doma
>  	return __arm_smmu_alloc_bitmap(smmu->context_map, start, count);
>  }
>  
> +static bool qcom_adreno_can_do_ttbr1(struct arm_smmu_device *smmu)
> +{
> +	const struct device_node *np = smmu->dev->of_node;
> +
> +	if (of_device_is_compatible(np, "qcom,msm8996-smmu-v2"))
> +		return false;
> +
> +	return true;
> +}
> +
>  static int qcom_adreno_smmu_init_context(struct arm_smmu_domain *smmu_domain,
>  		struct io_pgtable_cfg *pgtbl_cfg, struct device *dev)
>  {
> @@ -144,7 +154,8 @@ static int qcom_adreno_smmu_init_context(struct arm_smmu_domain *smmu_domain,
>  	 * be AARCH64 stage 1 but double check because the arm-smmu code assumes
>  	 * that is the case when the TTBR1 quirk is enabled
>  	 */
> -	if ((smmu_domain->stage == ARM_SMMU_DOMAIN_S1) &&
> +	if (qcom_adreno_can_do_ttbr1(smmu_domain->smmu) &&
> +	    (smmu_domain->stage == ARM_SMMU_DOMAIN_S1) &&
>  	    (smmu_domain->cfg.fmt == ARM_SMMU_CTX_FMT_AARCH64))
>  		pgtbl_cfg->quirks |= IO_PGTABLE_QUIRK_ARM_TTBR1;
>  
> -- 
> 2.31.0
>