Re: [PATCH 2/4] drm/i915: Adding Panel Filter function for DP

From: "Ville Syrjälä" <ville.syrjala@linux.intel.com>
To: "Zhang, Xiong Y" <xiong.y.zhang@intel.com>
Cc: "intel-gfx@lists.freedesktop.org" <intel-gfx@lists.freedesktop.org>
Subject: Re: [PATCH 2/4] drm/i915: Adding Panel Filter function for DP
Date: Tue, 18 Aug 2015 15:38:59 +0300	[thread overview]
Message-ID: <20150818123859.GJ5176@intel.com> (raw)
In-Reply-To: <20150814162844.GB5176@intel.com>

On Fri, Aug 14, 2015 at 07:28:44PM +0300, Ville Syrjälä wrote:
> 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@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

It occurs to me that we might actually go about this in a way that's
more like what you did. That is, we could expose the fixed mode as a
separate property from the user mode. That way the user could choose any
mode as the fixed mode, keeping the policy out from the kernel, and it
would be more in line with that we already do on LVDS/eDP. Obviously
we'd still need to add new border properties to give userspace full
freedom in setting up the pfit.

Another thing we could do with this approach is expose the pipe PF-ID
mode when the fixed mode is interlaced and the user mode is progressive.
And if both are interlaced, or there's just an interlaced used mode w/o
a fixed mode, we'd keep using IF-ID like we do today.

-- 
Ville Syrjälä
Intel OTC
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