Re: [PATCH 0/2] Optimization on intel HDMI detect and get_modes

["Kumar, Shobhit" <shobhit.kumar@intel.com>]

On 4/11/2014 8:18 PM, Sharma, Shashank wrote:
> Ok, I will change the implementation.
>
> Regards
> Shashank
> -----Original Message-----
> From: Daniel Vetter [mailto:daniel.vetter@ffwll.ch] On Behalf Of Daniel Vetter
> Sent: Friday, April 11, 2014 7:53 PM
> To: Sharma, Shashank
> Cc: Daniel Vetter; C, Ramalingam; Wang, Quanxian; intel-gfx
> Subject: Re: [Intel-gfx] [PATCH 0/2] Optimization on intel HDMI detect and get_modes
>
> On Fri, Apr 11, 2014 at 01:23:43PM +0000, Sharma, Shashank wrote:
>> Thanks for the comments,
>> Actually, we are not using live_status at all.
>>
>> The check for < gen6 is only for EDID caching. So if the HW is >= gen6 cache_edid.
>> Else do not cache EDID, so that we will not block any of the old HW, which might not be HPD capable.
>
> Oh, I've thought that this is incremental on top of something you already have.
>>
>> Does it sound ok now :) ?
>
> No. HPD is _NOT_ I repeat _NOT_ reliably. Not even on gen6+. live status simply reflects the hpd pin, if either doesn't work, then neither does the other one.
>
> Nacked-with-prejudice-by: Daniel Vetter <daniel.vetter@ffwll.ch>

Again re-starting the thread on this. Discussed this with Daniel on IRC 
and want to put the design agreed here for any further comments if any -

On detect call if no edid cached, then read full edid and cache. 
Assumption is that usermode will do the processing within 1s and we can 
just maintain this cache for 1s and clear. This will work also for 
panels which do not reliably assert HPD/Live status and also we get 
benefit of caching.

This will still fail compliance where we should not read any thing on 
ddc if live status is not detected. So plan is to add a compliance mode 
by way of module param which will be by default off. This code path will 
rely on HPD and Live status.

Regards
Shobhit