On Fri, Sep 30, 2022 at 11:01:52AM +0200, Thomas Zimmermann wrote: > Hi, > > thanks for reviewing. > > Am 29.09.22 um 21:03 schrieb Ville Syrjälä: > > On Thu, Sep 29, 2022 at 04:07:14PM +0200, Thomas Zimmermann wrote: > >> In drm_atomic_helper_check_crtc_state(), do not add a new plane state > >> to the global state if it does not exist already. Adding a new plane > >> state will results in overhead for the plane during the atomic-commit > >> step. > >> > >> For the test in drm_atomic_helper_check_crtc_state() to succeed, it is > >> important that the CRTC has an enabled primary plane after the commit. > >> This can be a newly enabled plane or an already enabled plane. So if a > >> plane is not part of the commit, use the plane's existing state. The new > >> helper drm_atomic_get_next_plane_state() returns the correct instance. > >> > >> Signed-off-by: Thomas Zimmermann <tzimmermann@xxxxxxx> > >> Fixes: d6b9af1097fe ("drm/atomic-helper: Add helper drm_atomic_helper_check_crtc_state()") > >> Cc: Thomas Zimmermann <tzimmermann@xxxxxxx> > >> Cc: Jocelyn Falempe <jfalempe@xxxxxxxxxx> > >> Cc: Maarten Lankhorst <maarten.lankhorst@xxxxxxxxxxxxxxx> > >> Cc: Maxime Ripard <mripard@xxxxxxxxxx> > >> Cc: David Airlie <airlied@xxxxxxxx> > >> Cc: Daniel Vetter <daniel@xxxxxxxx> > >> Cc: dri-devel@xxxxxxxxxxxxxxxxxxxxx > >> --- > >> drivers/gpu/drm/drm_atomic_helper.c | 4 +--- > >> include/drm/drm_atomic.h | 20 ++++++++++++++++++++ > >> 2 files changed, 21 insertions(+), 3 deletions(-) > >> > >> diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c > >> index 98cc3137c062..463d4f3fa443 100644 > >> --- a/drivers/gpu/drm/drm_atomic_helper.c > >> +++ b/drivers/gpu/drm/drm_atomic_helper.c > >> @@ -960,9 +960,7 @@ int drm_atomic_helper_check_crtc_state(struct drm_crtc_state *crtc_state, > >> > >> if (plane->type != DRM_PLANE_TYPE_PRIMARY) > >> continue; > >> - plane_state = drm_atomic_get_plane_state(state, plane); > >> - if (IS_ERR(plane_state)) > >> - return PTR_ERR(plane_state); > >> + plane_state = drm_atomic_get_next_plane_state(state, plane); > >> if (plane_state->fb && plane_state->crtc) { > > > > Hmm. Why this is even looking at these. If the plane is in the crtc's > > plane_mask then surely plane_state->crtc must already point to this > > crtc? And I don't think ->fb and ->crtc are allowed to disagree, so > > if one is set then surely the other one must be as well or we'd > > return an error at some point somewhere? > > Yeah, the crtc test is done for keeping consistency. Other places also > sometimes validate that these fields don't disagree. I'll remove the > crtc test in the next version. The fb test is the important one. What I'm asking how can you have crtc!=NULL && fb==NULL at all here? Some other plane state check function (can't remember which one specifically) should have rejected that. So either you're checking for impossible things, or there is a bug somewhere else. So to me it looks like it should be enough to just check the plane_mask and not even bother looking at the plane state at all. > > > > >> has_primary_plane = true; > >> break; > >> diff --git a/include/drm/drm_atomic.h b/include/drm/drm_atomic.h > >> index 10b1990bc1f6..4006f2d459e3 100644 > >> --- a/include/drm/drm_atomic.h > >> +++ b/include/drm/drm_atomic.h > >> @@ -623,6 +623,26 @@ drm_atomic_get_new_plane_state(struct drm_atomic_state *state, > >> return state->planes[drm_plane_index(plane)].new_state; > >> } > >> > >> +/** > >> + * drm_atomic_get_next_plane_state - get plane state after atomic commit > >> + * @state: global atomic state object > >> + * @plane: plane to grab > >> + * > >> + * This function returns the plane state that the given plane will have > >> + * after the atomic commit. This will be the new plane state if the plane > >> + * is part of the global atomic state, or the current state otherwise. > >> + */ > >> +static inline struct drm_plane_state * > >> +drm_atomic_get_next_plane_state(struct drm_atomic_state *state, > >> + struct drm_plane *plane) > >> +{ > >> + struct drm_plane_state *plane_state = drm_atomic_get_new_plane_state(state, plane); > >> + > >> + if (plane_state) > >> + return plane_state; > >> + return plane->state; > > > > You're not holding the appropriate lock so that does not look safe. Even > > if you know somewhere, somehow this sort of thing to be safe I don't > > think it's a good idea to promote this with any kind of official > > function because someone will shoot themselves in the foot with it. > > OK. It'll be inlined with locking added. > > Best regards > Thomas > > > > >> +} > >> + > >> /** > >> * drm_atomic_get_existing_connector_state - get connector state, if it exists > >> * @state: global atomic state object > >> -- > >> 2.37.3 > > > > -- > Thomas Zimmermann > Graphics Driver Developer > SUSE Software Solutions Germany GmbH > Maxfeldstr. 5, 90409 Nürnberg, Germany > (HRB 36809, AG Nürnberg) > Geschäftsführer: Ivo Totev -- Ville Syrjälä Intel