[PATCH 07/10] drm/edid: Don't send bogus aspect ratios in AVI infoframes

[Ville Syrjälä]

On Thu, Nov 16, 2017 at 08:31:36PM +0530, Sharma, Shashank wrote:
> Regards
> 
> Shashank
> 
> 
> On 11/13/2017 10:34 PM, Ville Syrjala wrote:
> > From: Ville Syrjälä <ville.syrjala at linux.intel.com>
> >
> > If the user mode would specify an aspect ratio other than 4:3 or 16:9
> > we now silently ignore it. Maybe a better apporoach is to return an
> > error? Let's try that.
> >
> > Also we must be careful that we don't try to send illegal picture
> > aspect in the infoframe as it's only capable of signalling none,
> > 4:3, and 16:9. Currently we're sending these bogus infoframes
> > whenever the cea mode specifies some other aspect ratio.
> >
> > Cc: Shashank Sharma <shashank.sharma at intel.com>
> > Cc: Sean Paul <seanpaul at chromium.org>
> > Cc: Jose Abreu <Jose.Abreu at synopsys.com>
> > Cc: Daniel Vetter <daniel.vetter at ffwll.ch>
> > Cc: Emil Velikov <emil.l.velikov at gmail.com>
> > Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
> > ---
> >   drivers/gpu/drm/drm_edid.c | 23 +++++++++++++++++------
> >   1 file changed, 17 insertions(+), 6 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
> > index 00aa98f3e55d..bafb3ee4ea97 100644
> > --- a/drivers/gpu/drm/drm_edid.c
> > +++ b/drivers/gpu/drm/drm_edid.c
> > @@ -4786,6 +4786,7 @@ drm_hdmi_avi_infoframe_from_display_mode(struct hdmi_avi_infoframe *frame,
> >   					 const struct drm_display_mode *mode,
> >   					 bool is_hdmi2_sink)
> >   {
> > +	enum hdmi_picture_aspect picture_aspect;
> >   	int err;
> >   
> >   	if (!frame || !mode)
> > @@ -4828,13 +4829,23 @@ drm_hdmi_avi_infoframe_from_display_mode(struct hdmi_avi_infoframe *frame,
> >   	 * Populate picture aspect ratio from either
> >   	 * user input (if specified) or from the CEA mode list.
> >   	 */
> > -	if (mode->picture_aspect_ratio == HDMI_PICTURE_ASPECT_4_3 ||
> > -		mode->picture_aspect_ratio == HDMI_PICTURE_ASPECT_16_9)
> > -		frame->picture_aspect = mode->picture_aspect_ratio;
> > -	else if (frame->video_code > 0)
> > -		frame->picture_aspect = drm_get_cea_aspect_ratio(
> > -						frame->video_code);
> > +	picture_aspect = mode->picture_aspect_ratio;
> > +	if (picture_aspect == HDMI_PICTURE_ASPECT_NONE)
> > +		picture_aspect = drm_get_cea_aspect_ratio(frame->video_code);
> This is slightly going in the loop.
> - During the modeset the driver cant specify the aspect ratio 
> information, as DRM layer lacks this support.
> - So we fill the VIC field, by comparing the mode with the 
> DRM_CEA_MODES[] list. This will pick the first mode
>    available in the list (regardless of its aspect ratio), and fill the 
> VIC, as we don't consider aspect ratio while comparing timings.
> - Again, now while sending the aspect ratio, we are picking up the VIC, 
> which may not be correct.
> 
> So if we have 720x480(4:3) and 720x480(16:9) in the list, as 4:3 is 
> first in list, we will always pick 4:3 aspect ratio.

Yes. The user didn't care about the aspect ratio (or rather couldn't
specify one) so we just pick one. Which is exactly what we've been
doing ever since we started sending the VIC in the infoframe.

> 
> - Shashank
> >   
> > +	/*
> > +	 * The infoframe can't convey anything but none, 4:3
> > +	 * and 16:9, so if the user has asked for anything else
> > +	 * we can only satisfy it by specifying the right VIC.
> > +	 */
> > +	if (picture_aspect > HDMI_PICTURE_ASPECT_16_9) {
> > +		if (picture_aspect !=
> > +		    drm_get_cea_aspect_ratio(frame->video_code))
> > +			return -EINVAL;
> > +		picture_aspect = HDMI_PICTURE_ASPECT_NONE;
> > +	}
> > +
> > +	frame->picture_aspect = picture_aspect;
> >   	frame->active_aspect = HDMI_ACTIVE_ASPECT_PICTURE;
> >   	frame->scan_mode = HDMI_SCAN_MODE_UNDERSCAN;
> >   

-- 
Ville Syrjälä
Intel OTC