linux-kernel - Re: [PATCH v2 4/7] drm/i915/display: Add handling for new "active bpc" property

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Message-ID: <YMIaqZnWTAiixwXJ@intel.com>
Date:   Thu, 10 Jun 2021 16:59:05 +0300
From:   Ville Syrjälä <ville.syrjala@...ux.intel.com>
To:     Maxime Ripard <maxime@...no.tech>
Cc:     Werner Sembach <wse@...edocomputers.com>, tzimmermann@...e.de,
        intel-gfx@...ts.freedesktop.org, sunpeng.li@....com,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        airlied@...ux.ie, amd-gfx@...ts.freedesktop.org,
        rodrigo.vivi@...el.com, alexander.deucher@....com,
        christian.koenig@....com
Subject: Re: [PATCH v2 4/7] drm/i915/display: Add handling for new "active
 bpc" property

On Thu, Jun 10, 2021 at 02:50:36PM +0200, Maxime Ripard wrote:
> Hi
> 
> On Tue, Jun 08, 2021 at 07:43:17PM +0200, Werner Sembach wrote:
> > This commits implements the "active bpc" drm property for the Intel GPU driver.
> > 
> > Signed-off-by: Werner Sembach <wse@...edocomputers.com>
> > ---
> >  drivers/gpu/drm/i915/display/intel_display.c | 14 ++++++++++++++
> >  drivers/gpu/drm/i915/display/intel_dp.c      |  8 ++++++--
> >  drivers/gpu/drm/i915/display/intel_dp_mst.c  |  4 +++-
> >  drivers/gpu/drm/i915/display/intel_hdmi.c    |  4 +++-
> >  4 files changed, 26 insertions(+), 4 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/i915/display/intel_display.c b/drivers/gpu/drm/i915/display/intel_display.c
> > index 64e9107d70f7..50c11b8770a7 100644
> > --- a/drivers/gpu/drm/i915/display/intel_display.c
> > +++ b/drivers/gpu/drm/i915/display/intel_display.c
> > @@ -10388,6 +10388,9 @@ static int intel_atomic_commit(struct drm_device *dev,
> >  {
> >  	struct intel_atomic_state *state = to_intel_atomic_state(_state);
> >  	struct drm_i915_private *dev_priv = to_i915(dev);
> > +	struct drm_connector *connector;
> > +	struct drm_connector_state *new_conn_state;
> > +	int i;
> >  	int ret = 0;
> >  
> >  	state->wakeref = intel_runtime_pm_get(&dev_priv->runtime_pm);
> > @@ -10456,6 +10459,17 @@ static int intel_atomic_commit(struct drm_device *dev,
> >  	intel_shared_dpll_swap_state(state);
> >  	intel_atomic_track_fbs(state);
> >  
> > +	/* Extract information from crtc to communicate it to userspace as connector properties */
> > +	for_each_new_connector_in_state(&state->base, connector, new_conn_state, i) {
> > +		struct intel_crtc *crtc = to_intel_crtc(new_conn_state->crtc);
> > +		if (crtc) {
> > +			struct intel_crtc_state *new_crtc_state = intel_atomic_get_new_crtc_state(state, crtc);
> > +			new_conn_state->active_bpc = new_crtc_state->pipe_bpp / 3;
> > +		}
> > +		else
> > +			new_conn_state->active_bpc = 0;
> > +	}
> > +
> 
> This seems fairly intrusive, but also commit / commit_tail might not be
> the best place to put this, we want to support it at the connector
> level.
> 
> Indeed, this will cause some issue if your HDMI output is a bridge for
> example, where the commit will be in an entirely different driver that
> has no dependency on the HDMI controller one.
> 
> I think it would be best to do that assignment in atomic_check. That
> way, if the userspace does a commit with DRM_MODE_ATOMIC_TEST_ONLY it
> would know what the output state would have been like.

DRM_MODE_ATOMIC_TEST_ONLY isn't allowed to change anything.

-- 
Ville Syrjälä
Intel