Re: [PATCH v5 3/5] drm/msm: Improve the a6xx page fault handler

[Akhil P Oommen <akhilpo@codeaurora.org>]

On 6/11/2021 3:14 AM, Rob Clark wrote:
> From: Jordan Crouse <jcrouse@codeaurora.org>
> 
> Use the new adreno-smmu-priv fault info function to get more SMMU
> debug registers and print the current TTBR0 to debug per-instance
> pagetables and figure out which GPU block generated the request.
> 
> Signed-off-by: Jordan Crouse <jcrouse@codeaurora.org>
> Signed-off-by: Rob Clark <robdclark@chromium.org>
> ---
>   drivers/gpu/drm/msm/adreno/a5xx_gpu.c |  4 +-
>   drivers/gpu/drm/msm/adreno/a6xx_gpu.c | 76 +++++++++++++++++++++++++--
>   drivers/gpu/drm/msm/msm_iommu.c       | 11 +++-
>   drivers/gpu/drm/msm/msm_mmu.h         |  4 +-
>   4 files changed, 87 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/gpu/drm/msm/adreno/a5xx_gpu.c b/drivers/gpu/drm/msm/adreno/a5xx_gpu.c
> index f46562c12022..eb030b00bff4 100644
> --- a/drivers/gpu/drm/msm/adreno/a5xx_gpu.c
> +++ b/drivers/gpu/drm/msm/adreno/a5xx_gpu.c
> @@ -1075,7 +1075,7 @@ bool a5xx_idle(struct msm_gpu *gpu, struct msm_ringbuffer *ring)
>   	return true;
>   }
>   
> -static int a5xx_fault_handler(void *arg, unsigned long iova, int flags)
> +static int a5xx_fault_handler(void *arg, unsigned long iova, int flags, void *data)
>   {
>   	struct msm_gpu *gpu = arg;
>   	pr_warn_ratelimited("*** gpu fault: iova=%08lx, flags=%d (%u,%u,%u,%u)\n",
> @@ -1085,7 +1085,7 @@ static int a5xx_fault_handler(void *arg, unsigned long iova, int flags)
>   			gpu_read(gpu, REG_A5XX_CP_SCRATCH_REG(6)),
>   			gpu_read(gpu, REG_A5XX_CP_SCRATCH_REG(7)));
>   
> -	return -EFAULT;
> +	return 0;
Shall we return -ENOSYS here to let the smmu handler print the fault 
debugging info? Due to the change here: iommu/arm-smmu: Add support for 
driver IOMMU fault handlers - arm_smmu_context_fault()

>   }
>   
>   static void a5xx_cp_err_irq(struct msm_gpu *gpu)
> diff --git a/drivers/gpu/drm/msm/adreno/a6xx_gpu.c b/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
> index c7f0ddb12d8f..fc19db10bff1 100644
> --- a/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
> +++ b/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
> @@ -1032,18 +1032,88 @@ static void a6xx_recover(struct msm_gpu *gpu)
>   	msm_gpu_hw_init(gpu);
>   }
>   
> -static int a6xx_fault_handler(void *arg, unsigned long iova, int flags)
> +static const char *a6xx_uche_fault_block(struct msm_gpu *gpu, u32 mid)
> +{
> +	static const char *uche_clients[7] = {
> +		"VFD", "SP", "VSC", "VPC", "HLSQ", "PC", "LRZ",
> +	};
> +	u32 val;
> +
> +	if (mid < 1 || mid > 3)
> +		return "UNKNOWN";
> +
> +	/*
> +	 * The source of the data depends on the mid ID read from FSYNR1.
> +	 * and the client ID read from the UCHE block
> +	 */
> +	val = gpu_read(gpu, REG_A6XX_UCHE_CLIENT_PF);
Are you sure gx rail is up at this point?

> +
> +	/* mid = 3 is most precise and refers to only one block per client */
> +	if (mid == 3)
> +		return uche_clients[val & 7];
> +
> +	/* For mid=2 the source is TP or VFD except when the client id is 0 */
> +	if (mid == 2)
> +		return ((val & 7) == 0) ? "TP" : "TP|VFD";
> +
> +	/* For mid=1 just return "UCHE" as a catchall for everything else */
> +	return "UCHE";
> +}
UCHE decoding scheme is different for a660. I am not sure who should 
handle that. Jonathan?

> +
> +static const char *a6xx_fault_block(struct msm_gpu *gpu, u32 id)
> +{
> +	if (id == 0)
> +		return "CP";
> +	else if (id == 4)
> +		return "CCU";
> +	else if (id == 6)
> +		return "CDP Prefetch";
I guess id == 7 is not possible here.

> +
> +	return a6xx_uche_fault_block(gpu, id);
> +}
> +
> +#define ARM_SMMU_FSR_TF                 BIT(1)
> +#define ARM_SMMU_FSR_PF			BIT(3)
> +#define ARM_SMMU_FSR_EF			BIT(4)
> +
> +static int a6xx_fault_handler(void *arg, unsigned long iova, int flags, void *data)
>   {
>   	struct msm_gpu *gpu = arg;
> +	struct adreno_smmu_fault_info *info = data;
> +	const char *type = "UNKNOWN";
>   
> -	pr_warn_ratelimited("*** gpu fault: iova=%08lx, flags=%d (%u,%u,%u,%u)\n",
> +	/*
> +	 * Print a default message if we couldn't get the data from the
> +	 * adreno-smmu-priv
> +	 */
> +	if (!info) {
> +		pr_warn_ratelimited("*** gpu fault: iova=%.16lx flags=%d (%u,%u,%u,%u)\n",
>   			iova, flags,
>   			gpu_read(gpu, REG_A6XX_CP_SCRATCH_REG(4)),
>   			gpu_read(gpu, REG_A6XX_CP_SCRATCH_REG(5)),
>   			gpu_read(gpu, REG_A6XX_CP_SCRATCH_REG(6)),
>   			gpu_read(gpu, REG_A6XX_CP_SCRATCH_REG(7)));
>   
> -	return -EFAULT;
> +		return 0;
return -ENOSYS here so that the smmu driver prints some extra debug data?
> +	}
> +
> +	if (info->fsr & ARM_SMMU_FSR_TF)
> +		type = "TRANSLATION";
> +	else if (info->fsr & ARM_SMMU_FSR_PF)
> +		type = "PERMISSION";
> +	else if (info->fsr & ARM_SMMU_FSR_EF)
> +		type = "EXTERNAL";
> +
> +	pr_warn_ratelimited("*** gpu fault: ttbr0=%.16llx iova=%.16lx dir=%s type=%s source=%s (%u,%u,%u,%u)\n",
> +			info->ttbr0, iova,
> +			flags & IOMMU_FAULT_WRITE ? "WRITE" : "READ", type,
> +			a6xx_fault_block(gpu, info->fsynr1 & 0xff),
> +			gpu_read(gpu, REG_A6XX_CP_SCRATCH_REG(4)),
> +			gpu_read(gpu, REG_A6XX_CP_SCRATCH_REG(5)),
> +			gpu_read(gpu, REG_A6XX_CP_SCRATCH_REG(6)),
> +			gpu_read(gpu, REG_A6XX_CP_SCRATCH_REG(7)));
> +
> +	return 0;
>   }
>   
>   static void a6xx_cp_hw_err_irq(struct msm_gpu *gpu)
> diff --git a/drivers/gpu/drm/msm/msm_iommu.c b/drivers/gpu/drm/msm/msm_iommu.c
> index 50d881794758..6975b95c3c29 100644
> --- a/drivers/gpu/drm/msm/msm_iommu.c
> +++ b/drivers/gpu/drm/msm/msm_iommu.c
> @@ -211,8 +211,17 @@ static int msm_fault_handler(struct iommu_domain *domain, struct device *dev,
>   		unsigned long iova, int flags, void *arg)
>   {
>   	struct msm_iommu *iommu = arg;
> +	struct adreno_smmu_priv *adreno_smmu = dev_get_drvdata(iommu->base.dev);
> +	struct adreno_smmu_fault_info info, *ptr = NULL;
> +
> +	if (adreno_smmu->get_fault_info) {
> +		adreno_smmu->get_fault_info(adreno_smmu->cookie, &info);
> +		ptr = &info;
> +	}
> +
>   	if (iommu->base.handler)
> -		return iommu->base.handler(iommu->base.arg, iova, flags);
> +		return iommu->base.handler(iommu->base.arg, iova, flags, ptr);
> +
>   	pr_warn_ratelimited("*** fault: iova=%16lx, flags=%d\n", iova, flags);
>   	return 0;
>   }
> diff --git a/drivers/gpu/drm/msm/msm_mmu.h b/drivers/gpu/drm/msm/msm_mmu.h
> index 61ade89d9e48..a88f44c3268d 100644
> --- a/drivers/gpu/drm/msm/msm_mmu.h
> +++ b/drivers/gpu/drm/msm/msm_mmu.h
> @@ -26,7 +26,7 @@ enum msm_mmu_type {
>   struct msm_mmu {
>   	const struct msm_mmu_funcs *funcs;
>   	struct device *dev;
> -	int (*handler)(void *arg, unsigned long iova, int flags);
> +	int (*handler)(void *arg, unsigned long iova, int flags, void *data);
>   	void *arg;
>   	enum msm_mmu_type type;
>   };
> @@ -43,7 +43,7 @@ struct msm_mmu *msm_iommu_new(struct device *dev, struct iommu_domain *domain);
>   struct msm_mmu *msm_gpummu_new(struct device *dev, struct msm_gpu *gpu);
>   
>   static inline void msm_mmu_set_fault_handler(struct msm_mmu *mmu, void *arg,
> -		int (*handler)(void *arg, unsigned long iova, int flags))
> +		int (*handler)(void *arg, unsigned long iova, int flags, void *data))
Just curious, why hide the datatype of 'data' using 'void *' here?
>   {
>   	mmu->arg = arg;
>   	mmu->handler = handler;
>