[PATCH] drm/amdgpu/ctx: only reset stable pstate if the user changed it

[Lazar, Lijo]

On 5/10/2022 1:33 AM, Alex Deucher wrote:
> Track whether the user requested a stable pstate via the ctx
> IOCTL and only reset the pstate on context destroy if the user
> actually changed it.  This avoids changing the pstate on contex
> destroy if the user never changed it in the first place via the
> IOCTL.
> 
> Fixes: 8cda7a4f96e435 ("drm/amdgpu/UAPI: add new CTX OP to get/set stable pstates")
> Signed-off-by: Alex Deucher <alexander.deucher at amd.com>
> ---
>   drivers/gpu/drm/amd/amdgpu/amdgpu_ctx.c | 5 ++++-
>   drivers/gpu/drm/amd/amdgpu/amdgpu_ctx.h | 1 +
>   2 files changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ctx.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_ctx.c
> index 5981c7d9bd48..e4b0c6ec227c 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ctx.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ctx.c
> @@ -330,6 +330,8 @@ static int amdgpu_ctx_set_stable_pstate(struct amdgpu_ctx *ctx,
>   		adev->pm.stable_pstate_ctx = NULL;
>   	else
>   		adev->pm.stable_pstate_ctx = ctx;
> +
> +	ctx->stable_pstate_requested = true;
>   done:
>   	mutex_unlock(&adev->pm.stable_pstate_ctx_lock);
>   
> @@ -353,7 +355,8 @@ static void amdgpu_ctx_fini(struct kref *ref)
>   	}
>   
>   	if (drm_dev_enter(&adev->ddev, &idx)) {
> -		amdgpu_ctx_set_stable_pstate(ctx, AMDGPU_CTX_STABLE_PSTATE_NONE);
> +		if (ctx->stable_pstate_requested)
> +			amdgpu_ctx_set_stable_pstate(ctx, AMDGPU_CTX_STABLE_PSTATE_NONE);

Why not have the check inside amdgpu_ctx_set_stable_pstate - if current 
stable pstate is not the same as the requested one, then only switch. If 
the user has not made a request, it will be NONE and the call doesn't 
have any effect.

Thanks,
Lijo

>   		drm_dev_exit(idx);
>   	}
>   
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ctx.h b/drivers/gpu/drm/amd/amdgpu/amdgpu_ctx.h
> index d0cbfcea90f7..f03e842209b8 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ctx.h
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ctx.h
> @@ -53,6 +53,7 @@ struct amdgpu_ctx {
>   	unsigned long			ras_counter_ce;
>   	unsigned long			ras_counter_ue;
>   	uint32_t			stable_pstate;
> +	bool				stable_pstate_requested;
>   };
>   
>   struct amdgpu_ctx_mgr {
>