linux-kernel - Re: [PATCH v2] drm/msm/a6xx+: Don't let IB

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Message-ID: <4525d045-745a-4d8b-987e-45d3fa9917b5@quicinc.com>
Date: Sat, 15 Mar 2025 01:37:05 +0530
From: Akhil P Oommen <quic_akhilpo@...cinc.com>
To: Rob Clark <robdclark@...il.com>, <dri-devel@...ts.freedesktop.org>
CC: <linux-arm-msm@...r.kernel.org>, <freedreno@...ts.freedesktop.org>,
        "Rob
 Clark" <robdclark@...omium.org>,
        Connor Abbott <cwabbott0@...il.com>, "Sean
 Paul" <sean@...rly.run>,
        Konrad Dybcio <konradybcio@...nel.org>,
        Abhinav
 Kumar <quic_abhinavk@...cinc.com>,
        Dmitry Baryshkov <lumag@...nel.org>,
        "Marijn Suijten" <marijn.suijten@...ainline.org>,
        David Airlie
	<airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
        Jordan Crouse
	<jordan@...micpenguin.net>,
        Jonathan Marek <jonathan@...ek.ca>,
        open list
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] drm/msm/a6xx+: Don't let IB_SIZE overflow

On 3/15/2025 12:04 AM, Rob Clark wrote:
> From: Rob Clark <robdclark@...omium.org>
> 
> IB_SIZE is only b0..b19.  Starting with a6xx gen3, additional fields
> were added above the IB_SIZE.  Accidentially setting them can cause
> badness.  Fix this by properly defining the CP_INDIRECT_BUFFER packet
> and using the generated builder macro to ensure unintended bits are not
> set.
> 
> v2: add missing type attribute for IB_BASE
> 
> Reported-by: Connor Abbott <cwabbott0@...il.com>
> Fixes: a83366ef19ea ("drm/msm/a6xx: add A640/A650 to gpulist")
> Signed-off-by: Rob Clark <robdclark@...omium.org>
> ---
> Backport notes, prior to commit ae22a94997b8 ("drm/msm: import A2xx-A4xx
> XML display registers database"), just open code, ie:
> 
>    OUT_RING(ring, submit->cmd[i].size & 0xfffff);
> 
> Prior to commit af66706accdf ("drm/msm/a6xx: Add skeleton A7xx
> support"), a7xx_submit() did not exist so that hunk can be dropped.
> 
>  drivers/gpu/drm/msm/adreno/a6xx_gpu.c               | 8 ++++----
>  drivers/gpu/drm/msm/registers/adreno/adreno_pm4.xml | 7 +++++++
>  2 files changed, 11 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/gpu/drm/msm/adreno/a6xx_gpu.c b/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
> index d3978cfa3f20..ea52b7d0b212 100644
> --- a/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
> +++ b/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
> @@ -245,10 +245,10 @@ static void a6xx_submit(struct msm_gpu *gpu, struct msm_gem_submit *submit)
>  				break;
>  			fallthrough;
>  		case MSM_SUBMIT_CMD_BUF:
> -			OUT_PKT7(ring, CP_INDIRECT_BUFFER_PFE, 3);
> +			OUT_PKT7(ring, CP_INDIRECT_BUFFER, 3);
>  			OUT_RING(ring, lower_32_bits(submit->cmd[i].iova));
>  			OUT_RING(ring, upper_32_bits(submit->cmd[i].iova));
> -			OUT_RING(ring, submit->cmd[i].size);
> +			OUT_RING(ring, A5XX_CP_INDIRECT_BUFFER_3_IB_SIZE(submit->cmd[i].size));
>  			ibs++;
>  			break;
>  		}
> @@ -382,10 +382,10 @@ static void a7xx_submit(struct msm_gpu *gpu, struct msm_gem_submit *submit)
>  				break;
>  			fallthrough;
>  		case MSM_SUBMIT_CMD_BUF:
> -			OUT_PKT7(ring, CP_INDIRECT_BUFFER_PFE, 3);
> +			OUT_PKT7(ring, CP_INDIRECT_BUFFER, 3);
>  			OUT_RING(ring, lower_32_bits(submit->cmd[i].iova));
>  			OUT_RING(ring, upper_32_bits(submit->cmd[i].iova));
> -			OUT_RING(ring, submit->cmd[i].size);
> +			OUT_RING(ring, A5XX_CP_INDIRECT_BUFFER_3_IB_SIZE(submit->cmd[i].size));
>  			ibs++;
>  			break;
>  		}
> diff --git a/drivers/gpu/drm/msm/registers/adreno/adreno_pm4.xml b/drivers/gpu/drm/msm/registers/adreno/adreno_pm4.xml
> index 55a35182858c..a71bc6f16cbf 100644
> --- a/drivers/gpu/drm/msm/registers/adreno/adreno_pm4.xml
> +++ b/drivers/gpu/drm/msm/registers/adreno/adreno_pm4.xml
> @@ -2259,5 +2259,12 @@ opcode: CP_LOAD_STATE4 (30) (4 dwords)
>  	</reg32>
>  </domain>
>  
> +<domain name="CP_INDIRECT_BUFFER" width="32" varset="chip" prefix="chip" variants="A5XX-">
> +	<reg64 offset="0" name="IB_BASE" type="address"/>
> +	<reg32 offset="3" name="3">

Why is the offset 3 here? It looks to me that it doesn't match the code
above.

-Akhil.

> +		<bitfield name="IB_SIZE" low="0" high="19"/>
> +	</reg32>
> +</domain>
> +
>  </database>
>