[Intel-gfx] [PATCH 2/4] drm/i915: Adding Panel Filter function for DP

[Ville Syrjälä]

On Fri, Aug 14, 2015 at 05:12:57AM +0000, Zhang, Xiong Y wrote:
> > On Mon, Aug 10, 2015 at 03:26:09PM +0800, Xiong Zhang wrote:
> > > Only internal eDP, LVDS, DVI screen could set scalling mode, some
> > > customers need to set scalling mode for external DP, HDMI, VGA screen.
> > > Let's fulfill this.
> > >
> > > bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=90989
> > >
> > > Signed-off-by: Xiong Zhang <xiong.y.zhang at intel.com>
> > > ---
> > >  drivers/gpu/drm/i915/intel_dp.c | 63
> > > ++++++++++++++++++++++++++++-------------
> > >  1 file changed, 44 insertions(+), 19 deletions(-)
> > >
> > > diff --git a/drivers/gpu/drm/i915/intel_dp.c
> > > b/drivers/gpu/drm/i915/intel_dp.c index f1b9f93..2da334b 100644
> > > --- a/drivers/gpu/drm/i915/intel_dp.c
> > > +++ b/drivers/gpu/drm/i915/intel_dp.c
> > > @@ -207,7 +207,13 @@ intel_dp_mode_valid(struct drm_connector
> > *connector,
> > >  	int target_clock = mode->clock;
> > >  	int max_rate, mode_rate, max_lanes, max_link_clock;
> > >
> > > -	if (is_edp(intel_dp) && fixed_mode) {
> > > +	if (mode->clock < 10000)
> > > +		return MODE_CLOCK_LOW;
> > > +
> > > +	if (mode->flags & DRM_MODE_FLAG_DBLCLK)
> > > +		return MODE_H_ILLEGAL;
> > > +
> > > +	if (!intel_panel_scale_none(&intel_connector->panel)) {
> > >  		if (mode->hdisplay > fixed_mode->hdisplay)
> > >  			return MODE_PANEL;
> > >
> > > @@ -226,12 +232,6 @@ intel_dp_mode_valid(struct drm_connector
> > *connector,
> > >  	if (mode_rate > max_rate)
> > >  		return MODE_CLOCK_HIGH;
> > >
> > > -	if (mode->clock < 10000)
> > > -		return MODE_CLOCK_LOW;
> > > -
> > > -	if (mode->flags & DRM_MODE_FLAG_DBLCLK)
> > > -		return MODE_H_ILLEGAL;
> > > -
> > >  	return MODE_OK;
> > >  }
> > >
> > > @@ -1378,7 +1378,7 @@ intel_dp_compute_config(struct intel_encoder
> > *encoder,
> > >  	pipe_config->has_drrs = false;
> > >  	pipe_config->has_audio = intel_dp->has_audio && port != PORT_A;
> > >
> > > -	if (is_edp(intel_dp) && intel_connector->panel.fixed_mode) {
> > > +	if (!intel_panel_scale_none(&intel_connector->panel)) {
> > >  		intel_fixed_panel_mode(intel_connector->panel.fixed_mode,
> > >  				       adjusted_mode);
> > >
> > > @@ -4592,6 +4592,23 @@ static int intel_dp_get_modes(struct
> > drm_connector *connector)
> > >  	edid = intel_connector->detect_edid;
> > >  	if (edid) {
> > >  		int ret = intel_connector_update_modes(connector, edid);
> > > +
> > > +		if (ret && intel_connector->panel.fixed_mode == NULL) {
> > > +			/* init fixed mode as preferred mode for DP */
> > > +			struct drm_display_mode *fixed_mode = NULL;
> > > +			struct drm_display_mode *scan;
> > > +
> > > +			list_for_each_entry(scan, &connector->probed_modes, head) {
> > > +				if (scan->type & DRM_MODE_TYPE_PREFERRED)
> > > +					fixed_mode = drm_mode_duplicate(connector->dev,
> > > +									scan);
> > > +			}
> > > +
> > > +			if (fixed_mode)
> > > +				intel_panel_init(&intel_connector->panel,
> > > +						 fixed_mode, NULL);
> > > +		}
> > 
> > How are we supposed to get rid of a stale fixed_mode when some other
> > display gets plugged in?
> [Zhang, Xiong Y] Thanks so much for your good question. Yes, we should clear the
> stale fitting_mode and fixed_mode when display is disconnect in 
> intel_dp_hpd_pulse() function.
> > 
> > Also what would happen if the preferred mode can't be supported due to some
> > source limitation?
> [Zhang, Xiong Y] In this case, which mode should be selected as fixed_mode ?

At the very least we should make sure it's a mode we can use.

> As you said maybe kernel isn't the right place to do such decision.

There are a lot of options how we could pick the mode. Eg. might want to
pick the next largest mode, and if there is none try to pick the largest
smaller mode (since pfit can't downscale by much). Also should we try to
pick an intelaced mode if the user requested one etc. Lots of open
questions how this policy should be handled. Would be easier to punt it
all to userspace, which would also avoid the kernel policy doing the
wrong thing when userspace knows what it wants.

> > 
> > In general I'm not entirely happy with having this kind of policy in the kernel.
> > I'd much prefer if we could get crtc size and border properties done so that
> > userspace could set up the scaling any which way it chooses.
> [Zhang, Xiong Y] Could you give more detail about your preference ?

The idea would be to expose some sort of crtc size properties that would
provide pipe_src_{w,h}, and the mode would provide the actual display
timings as it does today. And if we add some kind of border properties
to control the output size of the pfit (since the mode doesn't have that
information) userspace could do whatever it pleased.

I think the last attempt just sort of died out during review:
http://lists.freedesktop.org/archives/intel-gfx/2014-August/050732.html

-- 
Ville Syrjälä
Intel OTC