linux-kernel - Re: [PATCH] iommu/arm-smmu-qcom: Work around SDM845 Adreno SMMU w/ 16K pages

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Message-ID: <CAF6AEGsV7xfknnJ+-sQdHvzqCMc9=TFy6L3e6cM52MaaE3HNfw@mail.gmail.com>
Date: Tue, 30 Jul 2024 09:39:42 -0700
From: Rob Clark <robdclark@...il.com>
To: Konrad Dybcio <konradybcio@...nel.org>
Cc: Bjorn Andersson <andersson@...nel.org>, Will Deacon <will@...nel.org>, 
	Robin Murphy <robin.murphy@....com>, Joerg Roedel <joro@...tes.org>, 
	Marijn Suijten <marijn.suijten@...ainline.org>, iommu@...ts.linux.dev, 
	linux-arm-msm@...r.kernel.org, linux-arm-kernel@...ts.infradead.org, 
	linux-kernel@...r.kernel.org, Konrad Dybcio <konrad.dybcio@...aro.org>, 
	Sumit Semwal <sumit.semwal@...aro.org>
Subject: Re: [PATCH] iommu/arm-smmu-qcom: Work around SDM845 Adreno SMMU w/
 16K pages

On Mon, Jul 29, 2024 at 1:37 AM Konrad Dybcio <konradybcio@...nel.org> wrote:
>
> From: Konrad Dybcio <konrad.dybcio@...aro.org>
>
> SDM845's Adreno SMMU is unique in that it actually advertizes support
> for 16K (and 32M) pages, which doesn't hold for newer SoCs.
>
> This however, seems either broken in the hardware implementation, the
> hypervisor middleware that abstracts the SMMU, or there's a bug in the
> Linux kernel somewhere down the line that nobody managed to track down.
>
> Booting SDM845 with 16K page sizes and drm/msm results in:
>
> *** gpu fault: ttbr0=0000000000000000 iova=000100000000c000 dir=READ
> type=TRANSLATION source=CP (0,0,0,0)
>
> right after loading the firmware. The GPU then starts spitting out
> illegal intstruction errors, as it's quite obvious that it got a
> bogus pointer.
>
> Hide 16K support on SDM845's Adreno SMMU to work around this.
>
> Reported-by: Sumit Semwal <sumit.semwal@...aro.org>
> Signed-off-by: Konrad Dybcio <konrad.dybcio@...aro.org>
> ---
> There's a mismatch in sender/committer addresses but that's "fine":
> https://lore.kernel.org/linux-usb/2024072734-scenic-unwilling-71ea@gregkh/
> ---
>  drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c | 10 ++++++++++
>  1 file changed, 10 insertions(+)
>
> diff --git a/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c b/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c
> index 36c6b36ad4ff..d25825c05817 100644
> --- a/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c
> +++ b/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c
> @@ -338,6 +338,15 @@ static int qcom_smmu_cfg_probe(struct arm_smmu_device *smmu)
>         return 0;
>  }
>
> +static int qcom_adreno_smmuv2_cfg_probe(struct arm_smmu_device *smmu)
> +{
> +       /* SDM845 Adreno SMMU advertizes 16K pages support, but something is broken */
> +       if (of_device_is_compatible(smmu->dev->of_node, "qcom,sdm845-smmu-v2"))
> +               smmu->features &= ~ARM_SMMU_FEAT_FMT_AARCH64_16K;

jfwiw, it looks like we need this for sc7180 as well.. probably just
remove the "if" and mask out 16K for all smmu-v2, until we know that
there is somewhere that it _does_ work?

BR,
-R


> +
> +       return 0;
> +}
> +
>  static void qcom_smmu_write_s2cr(struct arm_smmu_device *smmu, int idx)
>  {
>         struct arm_smmu_s2cr *s2cr = smmu->s2crs + idx;
> @@ -436,6 +445,7 @@ static const struct arm_smmu_impl sdm845_smmu_500_impl = {
>
>  static const struct arm_smmu_impl qcom_adreno_smmu_v2_impl = {
>         .init_context = qcom_adreno_smmu_init_context,
> +       .cfg_probe = qcom_adreno_smmuv2_cfg_probe,
>         .def_domain_type = qcom_smmu_def_domain_type,
>         .alloc_context_bank = qcom_adreno_smmu_alloc_context_bank,
>         .write_sctlr = qcom_adreno_smmu_write_sctlr,
>
> ---
> base-commit: 931a3b3bccc96e7708c82b30b2b5fa82dfd04890
> change-id: 20240726-topic-845_gpu_smmu-ab738f7a013c
>
> Best regards,
> --
> Konrad Dybcio <konradybcio@...nel.org>
>