Re: [Intel-gfx] [PATCH 3/7] drm: Extract page_flip_{internal, atomic}()

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Tue, Nov 19, 2019 at 11:14:43AM +0100, Daniel Vetter wrote:
> On Fri, Nov 15, 2019 at 09:42:00PM +0200, Ville Syrjala wrote:
> > From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > 
> > Yank out the code for the plane->fb/old_fb/crtc handling from
> > the page flip path into page_flip_internal(), and provide a
> > simpler variant for atomic drivers.
> > 
> > We'll also move the fb vs. src viewport checks into the new
> > functions as they are slightly different between the two paths.
> > If the atomic .page_flip() implementations are guaranteed
> > to call drm_atomic_plane_check() we could even drop the check
> > entirely from page_flip_atomic(). For now toss in a FIXME.
> > 
> > v2: Bit more polish in page_flip_internal()
> > 
> > Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > ---
> >  drivers/gpu/drm/drm_plane.c | 159 +++++++++++++++++++++++-------------
> >  1 file changed, 102 insertions(+), 57 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/drm_plane.c b/drivers/gpu/drm/drm_plane.c
> > index 38878da5b704..6052475a20a5 100644
> > --- a/drivers/gpu/drm/drm_plane.c
> > +++ b/drivers/gpu/drm/drm_plane.c
> > @@ -1031,13 +1031,109 @@ int drm_mode_cursor2_ioctl(struct drm_device *dev,
> >  	return drm_mode_cursor_common(dev, req, file_priv);
> >  }
> >  
> > +static int page_flip_check_fbs(const struct drm_framebuffer *fb,
> > +			       const struct drm_framebuffer *old_fb)
> > +{
> > +	/* The framebuffer is currently unbound, presumably
> > +	 * due to a hotplug event, that userspace has not
> > +	 * yet discovered.
> > +	 */
> > +	if (!old_fb)
> > +		return -EBUSY;
> > +
> > +	if (old_fb->format != fb->format) {
> > +		DRM_DEBUG_KMS("Page flip is not allowed to change frame buffer format.\n");
> > +		return -EINVAL;
> > +	}
> > +
> > +	return 0;
> > +}
> > +
> > +static int page_flip_internal(struct drm_crtc *crtc,
> > +			      struct drm_framebuffer *fb,
> > +			      struct drm_pending_vblank_event *e,
> > +			      u32 flags,
> > +			      u32 target_vblank,
> > +			      struct drm_modeset_acquire_ctx *ctx)
> > +{
> > +	struct drm_plane *plane = crtc->primary;
> > +	int ret;
> > +
> > +	WARN_ON(drm_drv_uses_atomic_modeset(crtc->dev));
> > +
> > +	ret = drm_crtc_check_viewport(crtc, crtc->x, crtc->y,
> > +				      &crtc->mode, fb);
> > +	if (ret)
> > +		return ret;
> > +
> > +	ret = page_flip_check_fbs(fb, plane->fb);
> > +	if (ret)
> > +		return ret;
> > +
> > +	plane->old_fb = plane->fb;
> > +	if (crtc->funcs->page_flip_target)
> > +		ret = crtc->funcs->page_flip_target(crtc, fb, e, flags,
> > +						    target_vblank, ctx);
> > +	else
> > +		ret = crtc->funcs->page_flip(crtc, fb, e, flags, ctx);
> > +	if (ret) {
> > +		plane->old_fb = NULL;
> > +		return ret;
> > +	}
> > +
> > +	plane->fb = fb;
> > +	drm_framebuffer_get(plane->fb);
> > +
> > +	drm_framebuffer_put(plane->old_fb);
> > +	plane->old_fb = NULL;
> > +
> > +	return 0;
> > +}
> > +
> > +static int page_flip_atomic(struct drm_crtc *crtc,
> > +			    struct drm_framebuffer *fb,
> > +			    struct drm_pending_vblank_event *e,
> > +			    u32 flags,
> > +			    u32 target_vblank,
> > +			    struct drm_modeset_acquire_ctx *ctx)
> > +{
> > +	struct drm_plane *plane = crtc->primary;
> > +	struct drm_plane_state *plane_state = plane->state;
> > +	int ret;
> > +
> > +	WARN_ON(!drm_drv_uses_atomic_modeset(crtc->dev));
> > +
> > +	/*
> > +	 * FIXME: Can we assume all drivers end up calling
> > +	 * drm_atomic_plane_check() in their page flip paths?
> > +	 * If so we could remove this.
> > +	 */
> 
> This is definitely wrong, core has to check these. Currently no driver
> checks this at all. I think you're thinking of
> drm_atomic_helper_check_plane_state().

No, I'm thinking of drm_atomic_plane_check(). That one already does the
"does the src rect fit into the fb" check. It gets called from
drm_atomic_commit()->drm_atomic_check_only() but I wasn't sure if some
drivers might take some short circuit path past that for page_flip().

> 
> That aside I'm kinda not getting the point of the shuffling/cleanup in the
> first 4 patches here, so will skip them.

The point was to get that legacy plane->fb/old_fb stuff totally
out from the atomic codepath. Right now it's polluting the
supposedly higher level code shared by both atomic and legacy
drivers.

> -Daniel
> 
> > +	ret = drm_framebuffer_check_src_coords(plane_state->src_x,
> > +					       plane_state->src_y,
> > +					       plane_state->src_w,
> > +					       plane_state->src_h,
> > +					       fb);
> > +	if (ret)
> > +		return ret;
> > +
> > +	ret = page_flip_check_fbs(fb, plane_state->fb);
> > +	if (ret)
> > +		return ret;
> > +
> > +	if (crtc->funcs->page_flip_target)
> > +		return crtc->funcs->page_flip_target(crtc, fb, e, flags,
> > +						     target_vblank, ctx);
> > +	else
> > +		return crtc->funcs->page_flip(crtc, fb, e, flags, ctx);
> > +}
> > +
> >  int drm_mode_page_flip_ioctl(struct drm_device *dev,
> >  			     void *data, struct drm_file *file_priv)
> >  {
> >  	struct drm_mode_crtc_page_flip_target *page_flip = data;
> >  	struct drm_crtc *crtc;
> >  	struct drm_plane *plane;
> > -	struct drm_framebuffer *fb, *old_fb;
> > +	struct drm_framebuffer *fb;
> >  	struct drm_pending_vblank_event *e = NULL;
> >  	u32 target_vblank = page_flip->sequence;
> >  	struct drm_modeset_acquire_ctx ctx;
> > @@ -1145,65 +1241,14 @@ int drm_mode_page_flip_ioctl(struct drm_device *dev,
> >  	if (ret)
> >  		goto out;
> >  
> > -	if (plane->state)
> > -		old_fb = plane->state->fb;
> > +	if (drm_drv_uses_atomic_modeset(dev))
> > +		ret = page_flip_atomic(crtc, fb, e, page_flip->flags,
> > +				       target_vblank, &ctx);
> >  	else
> > -		old_fb = plane->fb;
> > -
> > -	if (old_fb == NULL) {
> > -		/* The framebuffer is currently unbound, presumably
> > -		 * due to a hotplug event, that userspace has not
> > -		 * yet discovered.
> > -		 */
> > -		ret = -EBUSY;
> > -		goto out;
> > -	}
> > -
> > -	if (plane->state) {
> > -		const struct drm_plane_state *state = plane->state;
> > -
> > -		ret = drm_framebuffer_check_src_coords(state->src_x,
> > -						       state->src_y,
> > -						       state->src_w,
> > -						       state->src_h,
> > -						       fb);
> > -	} else {
> > -		ret = drm_crtc_check_viewport(crtc, crtc->x, crtc->y,
> > -					      &crtc->mode, fb);
> > -	}
> > -	if (ret)
> > -		goto out;
> > -
> > -	if (old_fb->format != fb->format) {
> > -		DRM_DEBUG_KMS("Page flip is not allowed to change frame buffer format.\n");
> > -		ret = -EINVAL;
> > -		goto out;
> > -	}
> > -
> > -	plane->old_fb = plane->fb;
> > -	if (crtc->funcs->page_flip_target)
> > -		ret = crtc->funcs->page_flip_target(crtc, fb, e,
> > -						    page_flip->flags,
> > -						    target_vblank,
> > -						    &ctx);
> > -	else
> > -		ret = crtc->funcs->page_flip(crtc, fb, e, page_flip->flags,
> > -					     &ctx);
> > -	if (ret) {
> > -		/* Keep the old fb, don't unref it. */
> > -		plane->old_fb = NULL;
> > -	} else {
> > -		if (!plane->state) {
> > -			plane->fb = fb;
> > -			drm_framebuffer_get(fb);
> > -		}
> > -	}
> > +		ret = page_flip_internal(crtc, fb, e, page_flip->flags,
> > +					 target_vblank, &ctx);
> >  
> >  out:
> > -	if (plane->old_fb)
> > -		drm_framebuffer_put(plane->old_fb);
> > -	plane->old_fb = NULL;
> > -
> >  	if (ret == -EDEADLK) {
> >  		ret = drm_modeset_backoff(&ctx);
> >  		if (!ret)
> > -- 
> > 2.23.0
> > 
> > _______________________________________________
> > Intel-gfx mailing list
> > Intel-gfx@lists.freedesktop.org
> > https://lists.freedesktop.org/mailman/listinfo/intel-gfx
> 
> -- 
> Daniel Vetter
> Software Engineer, Intel Corporation
> http://blog.ffwll.ch

-- 
Ville Syrjälä
Intel
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