Re: [PATCH 2/2] iommu/arm-smmu-qcom: Move the adreno smmu specific impl earlier

[Jordan Crouse]

On Thu, Feb 25, 2021 at 03:54:10PM +0530, Sai Prakash Ranjan wrote:
> Adreno(GPU) SMMU and APSS(Application Processor SubSystem) SMMU
> both implement "arm,mmu-500" in some QTI SoCs and to run through
> adreno smmu specific implementation such as enabling split pagetables
> support, we need to match the "qcom,adreno-smmu" compatible first
> before apss smmu or else we will be running apps smmu implementation
> for adreno smmu and the additional features for adreno smmu is never
> set. For ex: we have "qcom,sc7280-smmu-500" compatible for both apps
> and adreno smmu implementing "arm,mmu-500", so the adreno smmu
> implementation is never reached because the current sequence checks
> for apps smmu compatible(qcom,sc7280-smmu-500) first and runs that
> specific impl and we never reach adreno smmu specific implementation.
> 
> Suggested-by: Akhil P Oommen <akhilpo@xxxxxxxxxxxxxx>
> Signed-off-by: Sai Prakash Ranjan <saiprakash.ranjan@xxxxxxxxxxxxxx>
> ---
> 
> Its either this or we add a new compatible for adreno smmu implementing
> arm,mmu-500 like "qcom,sc7280-adreno-smmu-500".
> 
> ---
>  drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c b/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c
> index bea3ee0dabc2..7d0fc2c8e72f 100644
> --- a/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c
> +++ b/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c
> @@ -345,11 +345,11 @@ struct arm_smmu_device *qcom_smmu_impl_init(struct arm_smmu_device *smmu)
>  {
>  	const struct device_node *np = smmu->dev->of_node;
>  
> -	if (of_match_node(qcom_smmu_impl_of_match, np))
> -		return qcom_smmu_create(smmu, &qcom_smmu_impl);
> -
>  	if (of_device_is_compatible(np, "qcom,adreno-smmu"))
>  		return qcom_smmu_create(smmu, &qcom_adreno_smmu_impl);
>  
> +	if (of_match_node(qcom_smmu_impl_of_match, np))
> +		return qcom_smmu_create(smmu, &qcom_smmu_impl);
> +

It would be good to add a comment here explaining the order here so we
don't accidentally reorganize ourselves back into a problem later.

Jordan

>  	return smmu;
>  }
> -- 
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