[Intel-gfx] [RFC 1/3] drm/i915: Roll intel_crtc->atomic into intel_crtc_state

[Maarten Lankhorst]

Op 01-09-15 om 17:48 schreef Ville Syrjälä:
> On Tue, Sep 01, 2015 at 08:30:05AM -0700, Matt Roper wrote:
>> On Tue, Sep 01, 2015 at 07:24:19AM +0200, Maarten Lankhorst wrote:
>>> Op 29-08-15 om 01:57 schreef Matt Roper:
>>>> Way back at the beginning of i915's atomic conversion I added
>>>> intel_crtc->atomic as a temporary dumping ground for "stuff to do
>>>> outside vblank evasion" flags since CRTC states weren't properly wired
>>>> up and tracked at that time.  We've had proper CRTC state tracking for a
>>>> while now, so there's really no reason for this hack to continue to
>>>> exist.  Moving forward we want to store intermediate crtc/plane state
>>>> data for modesets in addition to the final state, so moving these fields
>>>> into the proper state object allows us to properly compute them for both
>>>> the intermediate and final state.
>>>>
>>>> Signed-off-by: Matt Roper <matthew.d.roper at intel.com>
>>>> ---
>>> Can I shoot this patch down? It's better to add a field 'wm_changed'
>>> to the crtc_state, which gets reset to false for each crtc_state
>>> duplication. It's needed for checking if a cs pageflip can be done for
>>> atomic. It would remove the duplication of some checks there.
>>>
>>> The other atomic state members will die soon. I already have some
>>> patches to achieve that. :)
>>>
>>> I'm not sure if an intermediate state is a good idea. Any code that
>>> disables a crtc should only be looking at the old state.
>>> pre_plane_update runs all stuff in preparation for disabling planes,
>>> while post_plane_update runs everything needed for enabling planes. So
>>> no need to split it up I think, maybe put in some intermediate
>>> watermarks in intel_atomic_state, but no need for a full crtc_state.
>> Well, the intermediate state stuff was requested by Ville in response to
>> my watermark series, so I posted these patches as an RFC to make sure I
>> was understanding what he was looking for properly.
>>
>> Ville, can you comment?
> My opinion is that the current "disable is special" way of doing things
> is quite horrible. For one it makes it really hard to reason about what
> happens to a plane or crtc during the modeset. It's not just off->on,
> on->off, or same->same, but can be on->off->on. With the intermediate
> state in place, there can only be one transition, so really easy to
> think about what's going on.
pre_plane_update deals with all stuff related to disabling planes, while post_plane_update deals with changes after enabling.

If the crtc goes from on -> off only you could just hammer in the final values after the disable.

While for off->on or on->off->on you can put in the final values in .crtc_enable before lighting the pipe. I don't see why wm's would need more transitions.
> It'll also mean don't have to sprinkle silly wm update calls all over
> the modeset path. They will just get updated in response to the plane
> state changes. Same for IPS/FBC etc.
IPS and FBC are already calculated correctly in response to modesets.

~Maarten