Re: [PATCH v3 01/10] drm: Add atomic variants of enable/disable to encoder helper funcs

From: Daniel Vetter <daniel@ffwll.ch>
To: Sean Paul <sean@poorly.run>
Cc: dri-devel <dri-devel@lists.freedesktop.org>,
	"Sean Paul" <seanpaul@chromium.org>,
	"Ville Syrjälä" <ville.syrjala@linux.intel.com>,
	"Maarten Lankhorst" <maarten.lankhorst@linux.intel.com>,
	"Maxime Ripard" <maxime.ripard@bootlin.com>,
	"David Airlie" <airlied@linux.ie>,
	"Linux Kernel Mailing List" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v3 01/10] drm: Add atomic variants of enable/disable to encoder helper funcs
Date: Fri, 3 May 2019 16:08:14 +0200	[thread overview]
Message-ID: <CAKMK7uHO6rT=khqFrG7Saxxk_NZCC=rCYwATLUt1Cd_z+gh4rQ@mail.gmail.com> (raw)
In-Reply-To: <20190503123452.GG17077@art_vandelay>

On Fri, May 3, 2019 at 2:34 PM Sean Paul <sean@poorly.run> wrote:
>
> On Fri, May 03, 2019 at 09:51:30AM +0200, Daniel Vetter wrote:
> > On Thu, May 02, 2019 at 03:49:43PM -0400, Sean Paul wrote:
> > > From: Sean Paul <seanpaul@chromium.org>
> > >
> > > This patch adds atomic_enable and atomic_disable callbacks to the
> > > encoder helpers. This will allow encoders to make informed decisions in
> > > their start-up/shutdown based on the committed state.
> > >
> > > Aside from the new hooks, this patch also introduces the new signature
> > > for .atomic_* functions going forward. Instead of passing object state
> > > (well, encoders don't have atomic state, but let's ignore that), we pass
> > > the entire atomic state so the driver can inspect more than what's
> > > happening locally.
> > >
> > > This is particularly important for the upcoming self refresh helpers.
> > >
> > > Changes in v3:
> > > - Added patch to the set
> > >
> > > Cc: Daniel Vetter <daniel@ffwll.ch>
> > > Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > > Signed-off-by: Sean Paul <seanpaul@chromium.org>
> > > ---
> > >  drivers/gpu/drm/drm_atomic_helper.c      |  6 +++-
> > >  include/drm/drm_modeset_helper_vtables.h | 45 ++++++++++++++++++++++++
> > >  2 files changed, 50 insertions(+), 1 deletion(-)
>
> /snip
>
> > > diff --git a/include/drm/drm_modeset_helper_vtables.h b/include/drm/drm_modeset_helper_vtables.h
> > > index 8f3602811eb5..de57fb40cb6e 100644
> > > --- a/include/drm/drm_modeset_helper_vtables.h
> > > +++ b/include/drm/drm_modeset_helper_vtables.h
> > > @@ -675,6 +675,51 @@ struct drm_encoder_helper_funcs {
> > >     enum drm_connector_status (*detect)(struct drm_encoder *encoder,
> > >                                         struct drm_connector *connector);
> > >
> > > +   /**
> > > +    * @atomic_disable:
> > > +    *
> > > +    * This callback should be used to disable the encoder. With the atomic
> > > +    * drivers it is called before this encoder's CRTC has been shut off
> > > +    * using their own &drm_crtc_helper_funcs.atomic_disable hook. If that
> > > +    * sequence is too simple drivers can just add their own driver private
> > > +    * encoder hooks and call them from CRTC's callback by looping over all
> > > +    * encoders connected to it using for_each_encoder_on_crtc().
> > > +    *
> > > +    * This callback is a variant of @disable that provides the atomic state
> > > +    * to the driver. It takes priority over @disable during atomic commits.
> > > +    *
> > > +    * This hook is used only by atomic helpers. Atomic drivers don't need
> > > +    * to implement it if there's no need to disable anything at the encoder
> > > +    * level. To ensure that runtime PM handling (using either DPMS or the
> > > +    * new "ACTIVE" property) works @atomic_disable must be the inverse of
> > > +    * @atomic_enable.
> > > +    */
> >
> > I'd add something like "For atomic drivers also consider @atomic_disable"
> > to the kerneldoc of @disable (before the NOTE: which is only relevant for
> > pre-atomic). Same for the enable side.
> >
> > > +   void (*atomic_disable)(struct drm_encoder *encoder,
> > > +                          struct drm_atomic_state *state);
> > > +
> > > +   /**
> > > +    * @atomic_enable:
> > > +    *
> > > +    * This callback should be used to enable the encoder. It is called
> > > +    * after this encoder's CRTC has been enabled using their own
> > > +    * &drm_crtc_helper_funcs.atomic_enable hook. If that sequence is
> > > +    * too simple drivers can just add their own driver private encoder
> > > +    * hooks and call them from CRTC's callback by looping over all encoders
> > > +    * connected to it using for_each_encoder_on_crtc().
> > > +    *
> > > +    * This callback is a variant of @enable that provides the atomic state
> > > +    * to the driver. It is called in place of @enable during atomic
> > > +    * commits.
> >
> > needs to be adjusted here for "takes priority".
>
> Can you clarify this comment? I'm a little fuzzy on what it means.

Further up I suggest that @atomic_disable should take priority over
all the others (plus explain why @disable is lower than @prepare,
because of the special semantics this has in legacy crtc helpers).
Once you do that you also need to adjust the wording in the kerneldoc
here (same wording as in @atomic_enable sounds good to me), i.e.
explain that @atomic_disable takes priority over all other hooks.
-Daniel

>
>
>
> > > +    *
> > > +    * This hook is used only by atomic helpers, for symmetry with @disable.
> > > +    * Atomic drivers don't need to implement it if there's no need to
> > > +    * enable anything at the encoder level. To ensure that runtime PM
> > > +    * handling (using either DPMS or the new "ACTIVE" property) works
> > > +    * @enable must be the inverse of @disable for atomic drivers.
> > > +    */
> > > +   void (*atomic_enable)(struct drm_encoder *encoder,
> > > +                         struct drm_atomic_state *state);
> > > +
> >
> > With the nits:
> >
> > Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
>
> Thanks!
>
> Sean
>
> >
> > >     /**
> > >      * @disable:
> > >      *
> > > --
> > > Sean Paul, Software Engineer, Google / Chromium OS
> > >
> >
> > --
> > Daniel Vetter
> > Software Engineer, Intel Corporation
> > http://blog.ffwll.ch
>
> --
> Sean Paul, Software Engineer, Google / Chromium OS
> _______________________________________________
> dri-devel mailing list
> dri-devel@lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/dri-devel


-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch