Re: [PATCH 7/7] drm/atomic: Reduce setplane locking

[Daniel Vetter <daniel@ffwll.ch>]

On Fri, Nov 15, 2019 at 09:42:04PM +0200, Ville Syrjala wrote:
> From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> 
> Currently setplane grabs all modeset locks, which seems a bit
> excessive. Let's reduce that to just the locks we really need
> on atomic drivers. For non-atomic drivers let's stick to the
> current scheme for now.
> 
> Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> ---
>  drivers/gpu/drm/drm_plane.c | 56 +++++++++++++++++++------------------
>  1 file changed, 29 insertions(+), 27 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_plane.c b/drivers/gpu/drm/drm_plane.c
> index ef0cc33b43ce..e40d8a93294b 100644
> --- a/drivers/gpu/drm/drm_plane.c
> +++ b/drivers/gpu/drm/drm_plane.c
> @@ -680,10 +680,14 @@ static int __setplane_internal(struct drm_plane *plane,
>  			       uint32_t src_w, uint32_t src_h,
>  			       struct drm_modeset_acquire_ctx *ctx)
>  {
> -	int ret = 0;
> +	int ret;
>  
>  	WARN_ON(drm_drv_uses_atomic_modeset(plane->dev));
>  
> +	ret = drm_modeset_lock_all_ctx(plane->dev, ctx);
> +	if (ret)
> +		return ret;

There's pre-nv50 nouveau and shmob which have planes and aren't atomic (if
I checked correctly), so we could probably forgo this, but also feels
like totally not worth the audit trouble.

Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>

> +
>  	/* No fb means shut it down */
>  	if (!fb) {
>  		plane->old_fb = plane->fb;
> @@ -767,32 +771,24 @@ static int setplane_internal(struct drm_plane *plane,
>  			     uint32_t crtc_w, uint32_t crtc_h,
>  			     /* src_{x,y,w,h} values are 16.16 fixed point */
>  			     uint32_t src_x, uint32_t src_y,
> -			     uint32_t src_w, uint32_t src_h)
> +			     uint32_t src_w, uint32_t src_h,
> +			     struct drm_modeset_acquire_ctx *ctx)
>  {
> -	struct drm_modeset_acquire_ctx ctx;
> -	int ret;
> -
> -	DRM_MODESET_LOCK_ALL_BEGIN(plane->dev, ctx,
> -				   DRM_MODESET_ACQUIRE_INTERRUPTIBLE, ret);
> -
>  	if (drm_drv_uses_atomic_modeset(plane->dev))
> -		ret = __setplane_atomic(plane, crtc, fb,
> -					crtc_x, crtc_y, crtc_w, crtc_h,
> -					src_x, src_y, src_w, src_h, &ctx);
> +		return __setplane_atomic(plane, crtc, fb,
> +					 crtc_x, crtc_y, crtc_w, crtc_h,
> +					 src_x, src_y, src_w, src_h, ctx);
>  	else
> -		ret = __setplane_internal(plane, crtc, fb,
> -					  crtc_x, crtc_y, crtc_w, crtc_h,
> -					  src_x, src_y, src_w, src_h, &ctx);
> -
> -	DRM_MODESET_LOCK_ALL_END(ctx, ret);
> -
> -	return ret;
> +		return __setplane_internal(plane, crtc, fb,
> +					   crtc_x, crtc_y, crtc_w, crtc_h,
> +					   src_x, src_y, src_w, src_h, ctx);
>  }
>  
>  int drm_mode_setplane(struct drm_device *dev, void *data,
>  		      struct drm_file *file_priv)
>  {
>  	struct drm_mode_set_plane *plane_req = data;
> +	struct drm_modeset_acquire_ctx ctx;
>  	struct drm_plane *plane;
>  	struct drm_crtc *crtc = NULL;
>  	struct drm_framebuffer *fb = NULL;
> @@ -829,11 +825,22 @@ int drm_mode_setplane(struct drm_device *dev, void *data,
>  		}
>  	}
>  
> +	drm_modeset_acquire_init(&ctx, DRM_MODESET_ACQUIRE_INTERRUPTIBLE);
> +
> +retry:
>  	ret = setplane_internal(plane, crtc, fb,
>  				plane_req->crtc_x, plane_req->crtc_y,
>  				plane_req->crtc_w, plane_req->crtc_h,
>  				plane_req->src_x, plane_req->src_y,
> -				plane_req->src_w, plane_req->src_h);
> +				plane_req->src_w, plane_req->src_h, &ctx);
> +	if (ret == -EDEADLK) {
> +		ret = drm_modeset_backoff(&ctx);
> +		if (!ret)
> +			goto retry;
> +	}
> +
> +	drm_modeset_drop_locks(&ctx);
> +	drm_modeset_acquire_fini(&ctx);
>  
>  	if (fb)
>  		drm_framebuffer_put(fb);
> @@ -907,14 +914,9 @@ static int drm_mode_cursor_universal(struct drm_crtc *crtc,
>  		src_h = fb->height << 16;
>  	}
>  
> -	if (drm_drv_uses_atomic_modeset(dev))
> -		ret = __setplane_atomic(plane, crtc, fb,
> -					crtc_x, crtc_y, crtc_w, crtc_h,
> -					0, 0, src_w, src_h, ctx);
> -	else
> -		ret = __setplane_internal(plane, crtc, fb,
> -					  crtc_x, crtc_y, crtc_w, crtc_h,
> -					  0, 0, src_w, src_h, ctx);
> +	ret = setplane_internal(plane, crtc, fb,
> +				crtc_x, crtc_y, crtc_w, crtc_h,
> +				0, 0, src_w, src_h, ctx);
>  
>  	if (fb)
>  		drm_framebuffer_put(fb);
> -- 
> 2.23.0
> 
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-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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