On 08.08.2018 10:00, Leonard Crestez wrote: > On Tue, 2018-08-07 at 21:01 +0200, Stefan Agner wrote: >> On 06.08.2018 21:31, Leonard Crestez wrote: >> > The lcdif block is only powered on when display is active so plane >> > updates when not enabled are not valid. Writing to an unpowered IP block >> > is mostly ignored but can trigger bus errors on some chips. >> > >> > Prevent this situation by switching to drm_atomic_helper_commit_tail_rpm >> > and having the drm core ensure atomic_plane_update is only called while >> > the crtc is active. This avoids having to keep track of "enabled" bits >> > inside the mxsfb driver. >> > >> > This also requires handling the vblank event for disable from >> > ~~mxsfb_pipe_update~~ **mxsfb_pipe_disable**. >> >> Hm, I don't think this is a new requirement. Simple KMS Helper Reference >> clearly states that it should be called from update. >> >> Probably using drm_atomic_helper_commit_tail_rpm just exacerbates an >> issue which we haven't seen before... >> >> Since I think it is a general fix, I'd rather prefer have it in a >> separate commit. > > I wrote the commit message wrong, what I meant is that it requires > handling the vblank event from *disable*. > > Switching to atomic_helper_commit_tail_rpm means atomic_update is no > longer called when !state->active so nobody dispatches the last vblank > event for disabling the crtc. This causes a warning in > drm_atomic_helper_commit_hw_done on disable. Hm, I see, atomic_helper_commit_tail_rpm() uses DRM_PLANE_COMMIT_ACTIVE_ONLY, which leads to update() not being called for Simple KMS (since simple KMS uses the plane atomic_update() hook). I was looking in other drivers such as drivers/gpu/drm/pl111/pl111_display.c and was wondering why they do not need that in disable. But it makes sense since they do not use atomic_helper_commit_tail_rpm(), update does get called. Also note that pl111_display_update() uses drm_crtc_send_vblank_event() too if the crtc gets disabled: if (crtc->state->active && drm_crtc_vblank_get(crtc) == 0) drm_crtc_arm_vblank_event(crtc, event); else drm_crtc_send_vblank_event(crtc, event); The other users of atomic_helper_commit_tail_rpm(), exynos and sun4i, call drm_crtc_send_vblank_event() in the CRTC atomic_disable() hook. The Simple KMS equivalent of that is the disable hook. So it is really the change to _rpm() which requires to add drm_crtc_send_vblank_event() in disable. Having this two changes in a single commit indeed makes sense and is correct, sorry about the noise! Just fix the commit, and than I am fine with this. Reviewed-by: Stefan Agner <stefan@xxxxxxxx> -- Stefan > > Looking through the docs there seems to be a lot of complexity behind > vblank events so maybe I'm missing something. _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
