[Intel-gfx] HDMI 4k modes VIC

[Damien Lespiau]

On Wed, Oct 28, 2015 at 01:58:55PM +0000, Sharma, Shashank wrote:
>    Hi Damien
> 
>    This is regarding one of the patches:
>    drm: Add support for alternate clocks of 4k modes
>    (3f2f653378112c1453c0d83c81746a9225e4bc75)
> 
>    I am seeing that from function drm_match_hdmi_mode we are not returning
>    correct VIC's for 4k modes (listed in edid_4k_modes[])
>    Looks like we are returning VIC=(1, 2, 3, 4) for 4K modes (3840x2160 at 30Hz,
>    3840x2160 at 25Hz, 3840x2160 at 24Hz and 4096x2160 at 24Hz)

drm_match_hdmi_mode() doesn't return the VIC for the AVI infoframe, but
the VIC for the HDMI vendor specific infoframe. See section 8.2.3 of the
HDMI 1.4 spec.

>    But as per the CEA-861-F specs, the respective VIC should be (95, 94 and
>    93). The VIC returned is being used for writing AVI IF in
>    drm_hdmi_vendor_infoframe_from_display_mode.

That's not the AVI infoframe, that's the HDMI vendor specific infoframe.

>    Please help me to understand if there any specific reason for this, or am
>    I missing something in interpretation ?

Are you seeing a bug? it's totally possible, I've never used an actual
conformance tool when I wrote that code, so it's likely buggy and the
VIC in the AVI infoframe may well be wrong.

-- 
Damien