[Intel-gfx] [PATCH v3 7/7] drm: Allow drivers to leave encoder->possible_crtcs==0

[Daniel Vetter]

On Wed, Feb 12, 2020 at 10:07:55AM +0100, Daniel Vetter wrote:
> On Tue, Feb 11, 2020 at 07:14:51PM +0200, Ville Syrjälä wrote:
> > On Tue, Feb 11, 2020 at 06:05:45PM +0100, Daniel Vetter wrote:
> > > On Tue, Feb 11, 2020 at 06:22:08PM +0200, Ville Syrjala wrote:
> > > > From: Ville Syrjälä <ville.syrjala at linux.intel.com>
> > > > 
> > > > Let's simplify life of driver by allowing them to leave
> > > > encoder->possible_crtcs unset if they have no restrictions
> > > > in crtc<->encoder linkage. We'll just populate possible_crtcs
> > > > with the full crtc mask when registering the encoder so that
> > > > userspace doesn't have to deal with drivers not populating
> > > > this correctly.
> > > > 
> > > > Cc: Thomas Zimmermann <tzimmermann at suse.de>
> > > > Cc: Daniel Vetter <daniel at ffwll.ch>
> > > > Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
> > > > ---
> > > > We might not actually need/want this, but included it here for
> > > > future reference if that assumption turns out to be wrong.
> > > 
> > > I think this one is most definitely needed. _Lots_ of drivers get this
> > > toally wrong and just leave the value blank. It's encoded as official
> > > fallback in most userspace compositors.
> > 
> > OK. It's been a while since I dug around so can't really remmber how
> > this was being handled. I'll reorder before pushing.
> 
> Hm otoh having "works with all crtcs" as default is a bit dangerous,
> whereas the "cannot be cloned" default for possible_clones is perfectly
> safe.
> 
> So now I'm kinda not sure whether this is a bright idea, and we shouldn't
> just eat the cost of fixing up all the various WARNING backtraces your
> previous patch triggers. I've done a full review and the following look
> suspect:
> 
> - tegara/sor.c Strangely it's the only one, the other output drivers do
>   seem to set the possible_crtcs mask to something useful.

Strike that, it sets it using tegra_output_find_possible_crtcs().

I think everything is good and we really don't need this patch here to fix
up possible_crtcs.
-Daniel

> 
> Everything else seems to be fine. I'd say let's drop this patch, and I'm
> adding Thierry to shed some light on what's going on in tegra/sor.c.
> -Daniel
> 
> > 
> > > 
> > > Reviewed-by: Daniel Vetter <daniel.vetter at ffwll.ch>
> > > 
> > > > ---
> > > >  drivers/gpu/drm/drm_mode_config.c | 15 ++++++++++++++-
> > > >  include/drm/drm_encoder.h         |  4 ++++
> > > >  2 files changed, 18 insertions(+), 1 deletion(-)
> > > > 
> > > > diff --git a/drivers/gpu/drm/drm_mode_config.c b/drivers/gpu/drm/drm_mode_config.c
> > > > index 4c1b350ddb95..ce18c3dd0bde 100644
> > > > --- a/drivers/gpu/drm/drm_mode_config.c
> > > > +++ b/drivers/gpu/drm/drm_mode_config.c
> > > > @@ -592,6 +592,17 @@ static u32 full_crtc_mask(struct drm_device *dev)
> > > >  	return crtc_mask;
> > > >  }
> > > >  
> > > > +/*
> > > > + * Make life easy for drivers by allowing them to leave
> > > > + * possible_crtcs unset if there are not crtc<->encoder
> > > > + * restrictions.
> > > > + */
> > > > +static void fixup_encoder_possible_crtcs(struct drm_encoder *encoder)
> > > > +{
> > > > +	if (encoder->possible_crtcs == 0)
> > > > +		encoder->possible_crtcs = full_crtc_mask(encoder->dev);
> > > > +}
> > > > +
> > > >  static void validate_encoder_possible_crtcs(struct drm_encoder *encoder)
> > > >  {
> > > >  	u32 crtc_mask = full_crtc_mask(encoder->dev);
> > > > @@ -608,8 +619,10 @@ void drm_mode_config_validate(struct drm_device *dev)
> > > >  {
> > > >  	struct drm_encoder *encoder;
> > > >  
> > > > -	drm_for_each_encoder(encoder, dev)
> > > > +	drm_for_each_encoder(encoder, dev) {
> > > >  		fixup_encoder_possible_clones(encoder);
> > > > +		fixup_encoder_possible_crtcs(encoder);
> > > > +	}
> > > >  
> > > >  	drm_for_each_encoder(encoder, dev) {
> > > >  		validate_encoder_possible_clones(encoder);
> > > > diff --git a/include/drm/drm_encoder.h b/include/drm/drm_encoder.h
> > > > index b236269f41ac..bd033c5618bf 100644
> > > > --- a/include/drm/drm_encoder.h
> > > > +++ b/include/drm/drm_encoder.h
> > > > @@ -142,6 +142,10 @@ struct drm_encoder {
> > > >  	 * the bits for all &drm_crtc objects this encoder can be connected to
> > > >  	 * before calling drm_dev_register().
> > > >  	 *
> > > > +	 * As an exception to the above rule if any crtc can be connected to
> > > > +	 * the encoder the driver can leave @possible_crtcs set to 0. The core
> > > > +	 * will automagically fix this up by setting the bit for every crtc.
> > > > +	 *
> > > >  	 * You will get a WARN if you get this wrong in the driver.
> > > >  	 *
> > > >  	 * Note that since CRTC objects can't be hotplugged the assigned indices
> > > > -- 
> > > > 2.24.1
> > > > 
> > > 
> > > -- 
> > > Daniel Vetter
> > > Software Engineer, Intel Corporation
> > > http://blog.ffwll.ch
> > 
> > -- 
> > Ville Syrjälä
> > Intel
> 
> -- 
> Daniel Vetter
> Software Engineer, Intel Corporation
> http://blog.ffwll.ch

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