[PATCH] drm/edid: Add both 60Hz and 59.94Hz CEA modes to connector's mode list

[Daniel Vetter]

On Fri, May 31, 2013 at 8:56 PM, Andy Furniss <adf.lists at gmail.com> wrote:
> Daniel Vetter wrote:
>>
>> On Fri, May 31, 2013 at 03:23:41PM +0300, ville.syrjala at linux.intel.com
>> wrote:
>>>
>>> From: Ville Syrjälä <ville.syrjala at linux.intel.com>
>>>
>>> Having both modes can be beneficial for video playback cases. If you can
>>> match the video framerate exactly, and the audio and video clocks come
>>> from the same source, you should be able to avoid dropped/repeated
>>> frames without expensive operations such as resampling the audio to
>>> match video output rate.
>>>
>>> Rather than add both variants based on the CEA extension short video
>>> descriptors in do_cea_modes(), add only one variant there. Once all
>>> the EDID has been fully probed, do a loop over the entire probed mode
>>> list, during which we add the other variants for all modes that match
>>> CEA modes. This allows us to match modes that didn't come via the CEA
>>> short video descriptors. For example one Samsung TV here doesn't have
>>> the 640x480-60 mode as a SVD, but instead it's specified via a detailed
>>> timing descriptor.
>>>
>>> Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
>>> ---
>>> A few people requested this. Originally I was a bit opposed to it, but
>>> when I thought about it a bit more I figured if the audio and video
>>> clocks come from the same source (or happen to be close enough w/o
>>> significant drift), this could provide a better A/V sync w/o resampling
>>> tricks.
>>
>>
>> Yeah, I think this should be useful for a bunch of people. I've recently
>> chatted with a few xbmc folks on #irc and one thing they've requested is
>> mode fine-tuning. For DP we should have plenty of precision, but for HDMI
>> we'd need to (slightly) frob the vtotal ever so often to compensate. With
>> some runtime-tuning a la npt we should have perfect a/v sync without any
>> audio resampling.
>
>
> Apologies, for jumping in here, but assuming I haven't missed anything
> you've done already: do you have any plans for supporting CEA interlaced
> modes?
>
> That's assuming they actually need any more support - I only know that they
> are slightly wrong for me testing with radeon + my TV - are they tested and
> known to work / not work on intel hw?
>
> The symptom I get is not instantly obvious - the second half of the bottom
> line gets rendered and repeated as the top line.
>
> For me the reason that proper support could in theory be useful, is that
> were there in future a way to sync up properly,  my TV will do a nice "free"
> deinterlace. Even on a fast quad core PC doing one as good on cpu is not
> possible for HD 50i.

Interlaced modes are supported on all intel platforms (except i8xx, hw
can't do it there) and we have full support for CEA modes.
-Daniel
--
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch