Re: [PATCH] drm/msm/gpu: Fix crash when throttling GPU immediately during boot

[Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>]

On 4/29/25 10:33 AM, Stephan Gerhold wrote:
> There is a small chance that the GPU is already hot during boot. In that
> case, the call to of_devfreq_cooling_register() will immediately try to
> apply devfreq cooling, as seen in the following crash:
> 
>   Unable to handle kernel paging request at virtual address 0000000000014110
>   pc : a6xx_gpu_busy+0x1c/0x58 [msm]
>   lr : msm_devfreq_get_dev_status+0xbc/0x140 [msm]
>   Call trace:
>    a6xx_gpu_busy+0x1c/0x58 [msm] (P)
>    devfreq_simple_ondemand_func+0x3c/0x150
>    devfreq_update_target+0x44/0xd8
>    qos_max_notifier_call+0x30/0x84
>    blocking_notifier_call_chain+0x6c/0xa0
>    pm_qos_update_target+0xd0/0x110
>    freq_qos_apply+0x3c/0x74
>    apply_constraint+0x88/0x148
>    __dev_pm_qos_update_request+0x7c/0xcc
>    dev_pm_qos_update_request+0x38/0x5c
>    devfreq_cooling_set_cur_state+0x98/0xf0
>    __thermal_cdev_update+0x64/0xb4
>    thermal_cdev_update+0x4c/0x58
>    step_wise_manage+0x1f0/0x318
>    __thermal_zone_device_update+0x278/0x424
>    __thermal_cooling_device_register+0x2bc/0x308
>    thermal_of_cooling_device_register+0x10/0x1c
>    of_devfreq_cooling_register_power+0x240/0x2bc
>    of_devfreq_cooling_register+0x14/0x20
>    msm_devfreq_init+0xc4/0x1a0 [msm]
>    msm_gpu_init+0x304/0x574 [msm]
>    adreno_gpu_init+0x1c4/0x2e0 [msm]
>    a6xx_gpu_init+0x5c8/0x9c8 [msm]
>    adreno_bind+0x2a8/0x33c [msm]
>    ...
> 
> At this point we haven't initialized the GMU at all yet, so we cannot read
> the GMU registers inside a6xx_gpu_busy(). A similar issue was fixed before
> in commit 6694482a70e9 ("drm/msm: Avoid unclocked GMU register access in
> 6xx gpu_busy"): msm_devfreq_init() does call devfreq_suspend_device(), but
> unlike msm_devfreq_suspend(), it doesn't set the df->suspended flag
> accordingly. This means the df->suspended flag does not match the actual
> devfreq state after initialization and msm_devfreq_get_dev_status() will
> end up accessing GMU registers, causing the crash.
> 
> Fix this by setting df->suspended correctly during initialization.
> 
> Cc: stable@vger.kernel.org
> Fixes: 6694482a70e9 ("drm/msm: Avoid unclocked GMU register access in 6xx gpu_busy")
> Signed-off-by: Stephan Gerhold <stephan.gerhold@linaro.org>
> ---

Reviewed-by: Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>

Konrad