linux-kernel - Re: [PATCH] drm/msm: adreno: fix deferencing ifpc

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Message-ID: <04aec988-59ba-4c98-b922-510d86b10ea5@oss.qualcomm.com>
Date: Mon, 17 Nov 2025 16:02:25 +0100
From: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
To: Neil Armstrong <neil.armstrong@...aro.org>,
        Rob Clark <robin.clark@....qualcomm.com>, Sean Paul <sean@...rly.run>,
        Konrad Dybcio <konradybcio@...nel.org>,
        Dmitry Baryshkov <lumag@...nel.org>,
        Abhinav Kumar <abhinav.kumar@...ux.dev>,
        Jessica Zhang <jessica.zhang@....qualcomm.com>,
        Marijn Suijten <marijn.suijten@...ainline.org>,
        David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
        Akhil P Oommen <akhilpo@....qualcomm.com>
Cc: linux-arm-msm@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        freedreno@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drm/msm: adreno: fix deferencing ifpc_reglist when not
 declared

On 11/17/25 3:51 PM, Neil Armstrong wrote:
> On plaforms with an a7xx GPU not supporting IFPC, the ifpc_reglist
> if still deferenced in a7xx_patch_pwrup_reglist() which causes
> a kernel crash:
> Unable to handle kernel NULL pointer dereference at virtual address 0000000000000008
> ...
> pc : a6xx_hw_init+0x155c/0x1e4c [msm]
> lr : a6xx_hw_init+0x9a8/0x1e4c [msm]
> ...
> Call trace:
>   a6xx_hw_init+0x155c/0x1e4c [msm] (P)
>   msm_gpu_hw_init+0x58/0x88 [msm]
>   adreno_load_gpu+0x94/0x1fc [msm]
>   msm_open+0xe4/0xf4 [msm]
>   drm_file_alloc+0x1a0/0x2e4 [drm]
>   drm_client_init+0x7c/0x104 [drm]
>   drm_fbdev_client_setup+0x94/0xcf0 [drm_client_lib]
>   drm_client_setup+0xb4/0xd8 [drm_client_lib]
>   msm_drm_kms_post_init+0x2c/0x3c [msm]
>   msm_drm_init+0x1a4/0x228 [msm]
>   msm_drm_bind+0x30/0x3c [msm]
> ...
> 
> Check the validity of ifpc_reglist before deferencing the table
> to setup the register values.
> 
> Fixes: a6a0157cc68e ("drm/msm/a6xx: Enable IFPC on Adreno X1-85")
> Signed-off-by: Neil Armstrong <neil.armstrong@...aro.org>
> ---

I think it should be fine to skip calling this func altogether
if !ifpc || !pwrup_reglist

Although ifpc && !pwrup_reglist should probably scream very loud

Konrad