Re: [PATCH] drm/amdgpu: Check if smu.ppt_funcs is initialized before accessing

[Alex Deucher <alexdeucher-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>]

On Thu, Apr 18, 2019 at 12:01 PM <sunpeng.li@amd.com> wrote:
>
> From: Leo Li <sunpeng.li@amd.com>
>
> smu.ppt_funcs is only initialized for specific SMU versions.
>
> On a Hawaii ASIC, attempting to access the udev attribute
> ATTRS{power_dpm_state} will cause a null pointer deref in
> amdgpu_get_dpm_state() because of this.
>
> Fix by checking that ppt_funcs is initialized first.
>
> CC: Chengming Gui <Jack.Gui@amd.com>
> Signed-off-by: Leo Li <sunpeng.li@amd.com>
> ---
>  drivers/gpu/drm/amd/amdgpu/amdgpu_pm.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_pm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_pm.c
> index 4b7a076..7993623 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_pm.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_pm.c
> @@ -144,7 +144,7 @@ static ssize_t amdgpu_get_dpm_state(struct device *dev,
>         struct amdgpu_device *adev = ddev->dev_private;
>         enum amd_pm_state_type pm;
>
> -       if (adev->smu.ppt_funcs->get_current_power_state)
> +       if (adev->smu.ppt_funcs && adev->smu.ppt_funcs->get_current_power_state)

For consistency, I think we probably want something like:
if (is_support_sw_smu(adev) && adev->smu.ppt_funcs->get_current_power_state)

Either way:
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>

>                 pm = amdgpu_smu_get_current_power_state(adev);
>         else if (adev->powerplay.pp_funcs->get_current_power_state)
>                 pm = amdgpu_dpm_get_current_power_state(adev);
> --
> 2.7.4
>
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