On Sun, Jun 19, 2016 at 9:57 PM, Jyri Sarha <jsarha@xxxxxx> wrote: > Hi, > The documentation of drm_atomic_helper_check_modeset() says: > > "Drivers which update ->mode_changed (e.g. in their ->atomic_check hooks > if a plane update can't be done without a full modeset) _must_ call this > function afterwards after that change. It is permitted to call this > function multiple times for the same update, e.g. when the > ->atomic_check functions depend upon the adjusted dotclock for fifo > space allocation and watermark computation." > > Then drm_crtc_helper_funcs mode_fixup() callback documentations says: > > "Atomic drivers which need to inspect and adjust more state should > instead use the @atomic_check callback." > > Now an atomic driver that needs to do the both in the check phase: > update ->mode_changed and inspect and adjust the mode, is in trouble. > This is because any adjusted_mode modifications are reset by the > afterwards call of drm_atomic_helper_check_modeset(). > > I can get the atomic tilcdc driver working either: by using the > crtc_helper mode_fixup() calback, tuning the mode once more in > mode_set_nofb(), or calling drm_atomic_helper_check_modeset() last in > drm_mode_config_funcs atomic_check() callback. > > What is the right thing to do? Any of these three approaches (and > possibly updating the documentation), or some other option that I did > not think of? Tuning the mode once more in mode_set_nofb is no-go - that's in the commit phase, you're not allowed to change state objects then any more. Also note that the hint for mode_fixup is just a "should", and meant that way. You can split things up between mode_fixup and atomic_check callbacks. Pick whatever works best for you from the other 2 options. -Daniel -- Daniel Vetter Software Engineer, Intel Corporation +41 (0) 79 365 57 48 - http://blog.ffwll.ch _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
