On 10/02/2020 15:21, Ville Syrjälä wrote: > 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? > If (by using the drm_atomic_state pointer in old_crtc_state paremeter) I loop the planes trough with for_each_oldnew_plane_in_state(), I will only see the planes that were part of the drm atomic request sent from the user-space. I just tested that again. But is it a requirement that an user-space applications should always send the full state, and that the driver should assume that all mode_config objects that are not there in drm_atomic_state should be disabled? At least the implementation of drm_atomic_get_plane_state() (used by at least drm_atomic_normalize_zpos() and drm_mode_config_helper_suspend()) seems to suggest otherwise. When getting the plane state it first tries drm_atomic_get_existing_plane_state(), but if it can not find the state from the given drm_atomic_state, it goes down to the actual plane and calls plane->funcs->atomic_duplicate_state(plane) to get it from the plane-object itself. >> >>>> >>>> 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. > -- Texas Instruments Finland Oy, Porkkalankatu 22, 00180 Helsinki. Y-tunnus/Business ID: 0615521-4. Kotipaikka/Domicile: Helsinki _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
