linux-kernel - Re: [PATCH v2] iommu/arm-smmu: disable PRR on SM8250

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Message-ID: <c20a9713-6f8d-4c20-a031-dc448404d073@oss.qualcomm.com>
Date: Sun, 6 Jul 2025 19:51:55 +0530
From: Akhil P Oommen <akhilpo@....qualcomm.com>
To: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>,
        Rob Clark <robin.clark@....qualcomm.com>,
        Will Deacon <will@...nel.org>, Robin Murphy <robin.murphy@....com>,
        Joerg Roedel <joro@...tes.org>,
        Bibek Kumar Patro <quic_bibekkum@...cinc.com>
Cc: iommu@...ts.linux.dev, linux-arm-msm@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Akhil P Oommen <akhilpo@....qualcomm.com>
Subject: Re: [PATCH v2] iommu/arm-smmu: disable PRR on SM8250

On 7/5/2025 9:38 PM, Dmitry Baryshkov wrote:
> On SM8250 / QRB5165-RB5 using PRR bits resets the device, most likely
> because of the hyp limitations. Disable PRR support on that platform.
> 
> Fixes: 7f2ef1bfc758 ("iommu/arm-smmu: Add support for PRR bit setup")
> Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>

Reviewed-by: Akhil P Oommen <akhilpo@....qualcomm.com>

Unfortunately, there is no way to detect firmware support for PRR safely
from KMD.

-Akhil.

> ---
> I currently don't have access to other devices from these generations.
> It might be necessary to apply the same workaround to other platforms.
> ---
> Changes in v2:
> - Simplify the workaround as the issue seems to be limited to SM8250
>   only (Rob)
> - Link to v1: https://lore.kernel.org/r/20250705-iommu-fix-prr-v1-1-ef725033651c@oss.qualcomm.com
> ---
>  drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c | 3 ++-
>  1 file changed, 2 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 62874b18f6459ad9a8b0542ab81c24e3e745c53d..53d88646476e9f193a6275d9c3ee3d084c215362 100644
> --- a/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c
> +++ b/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c
> @@ -355,7 +355,8 @@ static int qcom_adreno_smmu_init_context(struct arm_smmu_domain *smmu_domain,
>  	priv->set_prr_addr = NULL;
>  
>  	if (of_device_is_compatible(np, "qcom,smmu-500") &&
> -			of_device_is_compatible(np, "qcom,adreno-smmu")) {
> +	    !of_device_is_compatible(np, "qcom,sm8250-smmu-500") &&
> +	    of_device_is_compatible(np, "qcom,adreno-smmu")) {
>  		priv->set_prr_bit = qcom_adreno_smmu_set_prr_bit;
>  		priv->set_prr_addr = qcom_adreno_smmu_set_prr_addr;
>  	}
> 
> ---
> base-commit: 7244e36657076b597ac21d118be9c0b0f15fc622
> change-id: 20250705-iommu-fix-prr-600451b1d304
> 
> Best regards,