On Sun, Feb 09, 2020 at 02:50:09PM +0200, Jyri Sarha wrote: > On 07/02/2020 20:45, Ville Syrjälä wrote: > > On Fri, Feb 07, 2020 at 08:26:17PM +0200, Jyri Sarha wrote: > >> On 07/02/2020 20:18, Jyri Sarha wrote: > >>> The old implementation of placing planes on the CRTC while configuring > >>> the planes was naive and relied on the order in which the planes were > >>> configured, enabled, and disabled. The situation where a plane's zpos > >>> was changed on the fly was completely broken. The usual symptoms of > >>> this problem was scrambled display and a flood of sync lost errors, > >>> when a plane was active in two layers at the same time, or a missing > >>> plane, in case when a layer was accidentally disabled. > >>> > >>> The rewrite takes a more straight forward approach when when HW is > >>> concerned. The plane positioning registers are in the CRTC (or > >>> actually OVR) register space and it is more natural to configure them > >>> in a one go when configuring the CRTC. This is easy since we have > >>> access to the whole atomic state when updating the CRTC configuration. > >>> > >> > >> While implementing this fix it caught me by surprise that > >> crtc->state->state (pointer up to full atomic state) is NULL when > >> crtc_enable() or -flush() is called. So I take the plane-state directly > >> from the plane->state and just assume that it is pointing to the same > >> atomic state with the crtc state I am having. I that alraight? > > > > IMO you should never use plane->state etc. Better pass down the > > full atomic state everywhere. Otherwise you can never even consider > > increasing the commit queue depth since you'd end up accessing the > > wrong state. > > > > Ok. I did explore this a bit and it starts to look like that I have to > store the planes' zpos values in the driver after all. Only the changes > are available in the drm_atomic_state being commited so I have to > maintain the full state myself. That is if I should not use plane->state > in crtc_enable() or -flush(). You have the full old and new states around for each crtc/plane/connector in the state. So not sure what you mean by having only the changes available? > > >> > >> Why is the crtc->state->state NULL? Is it a bug or is there some reason > >> to it? > > > > Currently swap_state() moves that state pointer from the new obj state > > to the old obj state, and clears the one in the new obj state. Not entirely > > sure why, but maybe just so there isn't a stale ->state pointer hanging > > around in the obj->state after the swap? > > > > I think a better way could be to not clobber the old obj state at > > all, leave the new_obj_state->state alone, and just clear the ->state > > pointer .duplicate_state(). But that would require reviewing a bunch > > of code to find all the places where old_obj_state->state gets used > > during the commit. > > > > I think those places are many, since at least I did not figure out any > other way to access the full commit behind the atomic helpers. I haven't examined how many drivers depend on the current behaviour. But fixing up the core/helpers should be pretty trivial. -- Ville Syrjälä Intel _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
