[PATCH 05/14] drm/crtc_helper: Disable and reenable primary plane in drm_helper_crtc_mode_set

[Daniel Vetter]

On Thu, May 26, 2016 at 11:02:55AM +0800, Ying Liu wrote:
> On Wed, May 25, 2016 at 6:30 PM, Daniel Vetter <daniel at ffwll.ch> wrote:
> > On Wed, May 25, 2016 at 05:37:41PM +0800, Ying Liu wrote:
> >> On Tue, May 24, 2016 at 6:57 PM, Daniel Vetter <daniel at ffwll.ch> wrote:
> >> > On Tue, May 24, 2016 at 06:10:44PM +0800, Liu Ying wrote:
> >> >> Since CRTC has already been disabled in crtc_funcs->prepare(), it doesn't hurt
> >> >> to disable the primary plane in drm_helper_crtc_mode_set() before enabling it
> >> >> in drm_helper_crtc_mode_set_base().  This makes those who reject active plane
> >> >> update in plane_funcs->atomic_check() happy.
> >> >
> >> > How/where exactly do you blow up?
> >> >>
> >> >> Signed-off-by: Liu Ying <gnuiyl at gmail.com>
> >> >> ---
> >> >>  drivers/gpu/drm/drm_crtc_helper.c | 9 +++++++++
> >> >>  1 file changed, 9 insertions(+)
> >> >>
> >> >> diff --git a/drivers/gpu/drm/drm_crtc_helper.c b/drivers/gpu/drm/drm_crtc_helper.c
> >> >> index 79555d2..7fabcd7 100644
> >> >> --- a/drivers/gpu/drm/drm_crtc_helper.c
> >> >> +++ b/drivers/gpu/drm/drm_crtc_helper.c
> >> >> @@ -1013,6 +1013,15 @@ int drm_helper_crtc_mode_set(struct drm_crtc *crtc, struct drm_display_mode *mod
> >> >>                       goto out;
> >> >>       }
> >> >>
> >> >> +     /*
> >> >> +      * It doesn't hurt to disable primary plane here since crtc is off
> >> >> +      * and we'll enable it again in drm_helper_crtc_mode_set_base()
> >> >> +      * below soon.
> >> >> +      */
> >> >> +     ret = drm_plane_helper_disable(crtc->primary);
> >> >
> >> > You can't call this helper from crtc helpers. drm_plane_helper_disable
> >> > assumes that a) you've already extracted universal plane support for the
> >> > primary plane by registering a proper drm_plane for it b) that you're
> >> > driver is at least partially using atomic hooks already.
> >> >
> >> > Both assumptions are wrong for all current users of this function.
> >> > drm_helper_crtc_mode_set() is purely a legacy helper for legecy drivers.
> >>
> >> Isn't the function a transitional helper, just as the kdoc claims?
> >> It looks all current users are sort of atomic users already.
> >
> > drm_helper_crtc_mode_set is exclusively used by legacy drivers.
> > drm_plane_helper_disable can be used for transitioning to atomic.
> 
> Again, please take a look at the kdoc of drm_helper_crtc_mode_set.
> It reads 'Besides the atomic plane helper functions for the primary
> plane the driver must also provide the ->mode_set_nofb callback
> to set up the CRTC.  This is a transitional helper useful for converting
> drivers to the atomic interfaces.'

Oops, my apologies, I mixed it all up in my head. Sorry for all the mess,
I'll start a new thread since this discussion here is a bit confusion now.
-Daniel


> > Calling the latter from the former means you break every non-transition
> > legacy driver.
> 
> drm_helper_crtc_mode_set calls drm_helper_crtc_mode_set_base.
> Both drm_helper_crtc_mode_set_base and drm_plane_helper_disable
> call drm_plane_helper_commit, so they are somewhat counterparts,
> that is to say,  drm_helper_crtc_mode_set may call
> drm_plane_helper_disable technically.
> 
> Regards,
> Liu Ying
> 
> > -Daniel
> >
> >>
> >> Regards,
> >> Liu Ying
> >>
> >> > -Daniel
> >> >
> >> >> +     if (ret)
> >> >> +             goto out;
> >> >> +
> >> >>       swap(crtc->state, crtc_state);
> >> >>
> >> >>       crtc_funcs->mode_set_nofb(crtc);
> >> >> --
> >> >> 2.7.4
> >> >>
> >> >> _______________________________________________
> >> >> dri-devel mailing list
> >> >> dri-devel at lists.freedesktop.org
> >> >> https://lists.freedesktop.org/mailman/listinfo/dri-devel
> >> >
> >> > --
> >> > Daniel Vetter
> >> > Software Engineer, Intel Corporation
> >> > http://blog.ffwll.ch
> >
> > --
> > Daniel Vetter
> > Software Engineer, Intel Corporation
> > http://blog.ffwll.ch

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch