On Mon, Aug 22, 2016 at 04:23:36PM +0800, Ying Liu wrote:
> On Mon, Aug 22, 2016 at 3:53 PM, Daniel Vetter <daniel@xxxxxxxx> wrote:
> > On Mon, Aug 22, 2016 at 9:43 AM, Ying Liu <gnuiyl@xxxxxxxxx> wrote:
> >>>> +
> >>>> + /*
> >>>> + * The relevant plane's ->atomic_check callback may set
> >>>> + * crtc_state->mode_changed to be true when the active
> >>>> + * plane needs to be reconfigured. In this case and only
> >>>> + * this case, active_changed is false - we disable all the
> >>>> + * appropriate active planes here.
> >>>> + */
> >>>> + if (!crtc->state->active_changed) {
> >>>> + struct drm_plane *plane;
> >>>> +
> >>>> + drm_atomic_crtc_state_for_each_plane(plane, old_crtc_state) {
> >>>> + const struct drm_plane_helper_funcs *plane_funcs =
> >>>> + plane->helper_private;
> >>>> +
> >>>> + /*
> >>>> + * Filter out the plane which is explicitly required
> >>>> + * to be disabled by the user via atomic commit
> >>>> + * so that it won't be accidentally disabled twice.
> >>>> + */
> >>>> + if (!plane->state->crtc)
> >>>> + continue;
> >>>
> >>> I think the better place would be to do the filtering in commit_planes(),
> >>> not here. And would be great to include your patch to fix up
> >>> disable_planes_on_crtc(), too.
> >>
> >> Do you mean we can do the filtering by checking (!plane->state->crtc)
> >> right before plane_funcs->atomic_disable in commit_planes()?
> >> Won't it filter out all the apples?
> >> commit_planes() doesn't know whether the driver calls
> >> disable_planes_on_crtc() or not.
> >
> > You need to filter on needs_modeset(crtc_state), and it needs to be
> > optional like active_only, using a flag.
>
> Then, IIUC, the flag will be CRTC specific and be dynamically
> changeable. I'm not clear about the way to implement this.
>
> >
> >> imo, doing the filtering in crtc_funcs->atomic_disable is sane.
> >
> > It is not sane in general, since usually you need to call
> > disable_planes_on_crtc to avoid upsetting your hardware. And for that
>
> Calling disable_planes_on_crtc() in crtc_funcs->atomic_disable is
> a bit over-kill and will cause the issue of disabling plane twice, unless
> the filtering is done in disable_planes_on_crtc() (which was rejected
> by you on irc) or in commit_planes()?(which I'm not clear about
> the way to implement, as I mentioned before). So I chose to do the
> filtering in the imx-drm specific crtc_funcs->atomic_disable function.
For filtering in commit_planes I think the best plane is to
- add a new flag NO_DISABLE_AFTER_MODESET
- which does exactly what it says on the tin: If the commmit_planes helper
would call plane_funcs->atomic_disable, but
drm_atomic_crtc_needs_modeset() for that crtc is true then you skip the
->atomic_disable call.
This assumes that all disables have already been committed when disabling
the crtc. For a lot of hardware it only makes sense to set both this flag
and ACTIVE_ONLY, but there's probably some fun hardware out there where
this is not the case (yours seems to be one example).
Now it's not pretty to have 2 boolean arguments for the same function, so
we also need to convert that into a bitflag field. End result:
#define COMMIT_ACTIVE_ONLY BIT(0)
#define COMMIT_NO_DISABLE_AFTER_MODESET BIT(1)
Ofc kernel-doc should explain what the flags are for and when to use them.
void drm_atomic_helper_commit_planes(struct drm_device *dev,
struct drm_atomic_state *state,
unsigned flags);
A bit more work, but I think overall worth it.
> > use-case filtering in disable will lead to hung hardware. Which really
>
> Hung hardware due to filtering? How?
If you shut down the crtc and keep the planes running the hw dies. Yup,
this happens.
> > means that you need to filter in commit_planes.
>
> Really don't understand the rational for filtering in commit_planes...
> Did I miss anything?
See above, it might work for your driver, but it definitely restricts the
usefulness of the helpers in general. And helpers which are only useful
for 1 driver aren't useful.
I hope this explains my idea a bit better, otherwise probably best if you
ping me on irc.
-Daniel
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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