[PATCH] drm/drm_edid: correct VIC and HDMI_VIC under HDMI 2.0

[Lin, Wayne]

> -----Original Message-----
> From: Ville Syrjälä <ville.syrjala at linux.intel.com>
> Sent: Friday, October 4, 2019 10:24 PM
> To: Lin, Wayne <Wayne.Lin at amd.com>
> Cc: dri-devel at lists.freedesktop.org; amd-gfx at lists.freedesktop.org; Li, Sun
> peng (Leo) <Sunpeng.Li at amd.com>; Kazlauskas, Nicholas
> <Nicholas.Kazlauskas at amd.com>
> Subject: Re: [PATCH] drm/drm_edid: correct VIC and HDMI_VIC under HDMI
> 2.0
> 
> On Fri, Oct 04, 2019 at 10:41:20AM +0000, Lin, Wayne wrote:
> >
> >
> > ________________________________
> > From: Ville Syrjälä <ville.syrjala at linux.intel.com>
> > Sent: Thursday, October 3, 2019 21:29
> > To: Lin, Wayne <Wayne.Lin at amd.com>
> > Cc: dri-devel at lists.freedesktop.org <dri-devel at lists.freedesktop.org>;
> > amd-gfx at lists.freedesktop.org <amd-gfx at lists.freedesktop.org>; Li, Sun
> > peng (Leo) <Sunpeng.Li at amd.com>; Kazlauskas, Nicholas
> > <Nicholas.Kazlauskas at amd.com>
> > Subject: Re: [PATCH] drm/drm_edid: correct VIC and HDMI_VIC under HDMI
> > 2.0
> >
> > On Thu, Oct 03, 2019 at 06:49:05AM +0000, Lin, Wayne wrote:
> > >
> > >
> > > ________________________________
> > > From: Ville Syrjälä <ville.syrjala at linux.intel.com>
> > > Sent: Wednesday, October 2, 2019 19:58
> > > To: Lin, Wayne <Wayne.Lin at amd.com>
> > > Cc: dri-devel at lists.freedesktop.org
> > > <dri-devel at lists.freedesktop.org>; amd-gfx at lists.freedesktop.org
> > > <amd-gfx at lists.freedesktop.org>; Li, Sun peng (Leo)
> > > <Sunpeng.Li at amd.com>; Kazlauskas, Nicholas
> > > <Nicholas.Kazlauskas at amd.com>
> > > Subject: Re: [PATCH] drm/drm_edid: correct VIC and HDMI_VIC under
> > > HDMI 2.0
> > >
> > > On Tue, Sep 24, 2019 at 01:26:21PM +0800, Wayne Lin wrote:
> > > > In HDMI 1.4 defines 4k modes without specific aspect ratio.
> > > > However, in HDMI 2.0, adds aspect ratio attribute to distinguish
> > > > different 4k modes.
> > > >
> > > > According to Appendix E of HDMI 2.0 spec, source should use VSIF
> > > > to indicate VIC mode only when the mode is one defined in HDMI 1.4b 4K
> modes.
> > > > Otherwise, use AVI infoframes to convey VIC.
> > > >
> > > > eg: VIC_103 should use AVI infoframes and VIC_93 use VSIF
> > > >
> > > > When the sink is HDMI 2.0, current code in
> > > > drm_hdmi_avi_infoframe_from_display_mode will also force mode
> > > > VIC_103 to have VIC value 0. This violates the spec and needs to be
> corrected.
> > >
> > > > Where is that being done? We only set the AVI VIC to zero if we're
> > > > going to use the HDMI VIC instead.
> > >
> > > Appreciate for your time and apologize for not explaining it clearly.
> > > Current code in drm_hdmi_avi_infoframe_from_display_mode() will call
> > > drm_match_hdmi_mode() to set up vendor_if_vic. By checking
> > > drm_valid_hdmi_vic(vendor_if_vic) to see if the vic info should be
> > > conveyed by avi or not.
> > >
> > > But in drm_match_hdmi_mode(), code doesn't enable match_flags with
> > > DRM_MODE_MATCH_ASPECT_RATIO. I think it's due to HDMI1.4b doesn't
> > > specify 4K mode conveyed by HDMI VIC with particular aspect ratio.
> > > But in Appendix E of HDMI 2.0 spec, it specify only 4k modes with
> particular aspect ratio should use VSIF to convey.
> > > Hence, when the sink support HDMI 2.0 and set the mode to be
> > > VIC_103, calling
> > > drm_match_hdmi_mode(mode) will return vendor_if_vic = 3 (VIC_93 and
> > > VIC_103 are having the same timing but different aspect ratio). Thereafter
> will set the  frame->video_code to 0.
> > > However, VIC_103 should use AVI VIC according to HDMI 2.0 spec (only
> > > VIC: 93, 94, 95 &
> > > 98 should use VSIF).
> > >
> > > This patch try to revise that, when the sink support HDMI 2.0,
> > > drm_match_hdmi_mode() should also take aspect ratio into consideration.
> > > But for easy reading, I add another function
> "drm_match_hdmi_1_4_mode" to do so.
> >
> > > Seems rather convoluted. I think we should just add the aspect
> > > ratios to edid_4k_modes[]. Or is there some problem with that approach?
> >
> > Thanks for your time.
> >
> > Since HDMI 1.4b doesn't require edid_4k_modes[] with specific aspect
> > ratio, modes as the same timing in edid_4k_modes[] but with different
> > aspect ratios are also expected to convey VIC by VSIF to HDMI 1.4
> > sink. Might can't guarantee that there wont't be any compatibility side effect
> with that approach when the sink is HDMI 1.4b .
> 
> I think adding them should be fine. But while checking the existing code I
> noticed a few problems, so I sent out some fixes (cc:d you).

Thanks for your time and sorry for late reply.
I will try out those received fixes and leave messages there.

> 
> --
> Ville Syrjälä
> Intel

--
Wayne Lin