[Intel-gfx] [PATCH] drm/i915: Set edid from init and not from detect

[Sharma, Shashank]

Hi Daniel, Chris  

Gen7 and Gen8 platforms have a different live status register (0x61114) and we need not to rely on ISR on that. 
As Sonika mentioned, We have been using this register for our commercial releases, and found them reliable across a wide range of monitors. 

On the other hand, Bsepc clearly mentions, to check the live status before even try to read EDID. 
The current DRM nightly code doesn't do that, and we have received few errors from Gen7 Chromebooks where you can still read valid EDID on HDMI hot-unplug. 

So I think this patch and solution is ready, and it should go in. 

Regards
Shashank
-----Original Message-----
From: Daniel Vetter [mailto:daniel.vetter at ffwll.ch] On Behalf Of Daniel Vetter
Sent: Monday, July 13, 2015 8:27 PM
To: Jindal, Sonika
Cc: Chris Wilson; intel-gfx at lists.freedesktop.org; Sharma, Shashank
Subject: Re: [Intel-gfx] [PATCH] drm/i915: Set edid from init and not from detect

On Mon, Jul 13, 2015 at 05:29:12PM +0530, Jindal, Sonika wrote:
> 
> 
> On 7/13/2015 5:10 PM, Chris Wilson wrote:
> >On Mon, Jul 13, 2015 at 04:19:15PM +0530, Sonika Jindal wrote:
> >>During init_connector set the edid, then edid will be set/unset only 
> >>during hotplug. For the sake of older platforms where HPD is not 
> >>stable, let edid read happen from detect as well only if it is forced to do so.
> >>
> >>v2: Removing the 'force' check, instead let detect call read the 
> >>edid for platforms older than gen 7 (Shashank)
> >
> >That's enough worse. We now have a random gen check with no rationale 
> >for why you suddenly believe all manufacturers have fixed their wiring.
> >There is no reason to believe that gen7 suddenly works is there? If 
> >there is, why don't you mention it?
> >-Chris
> >
> This gen7 check is to be on the safer side not to affect older paltforms.
> For CHV/VLV, already the live status check is stable enough to 
> determine if we can read edid or not. In VPG production branches we 
> have this patch already available and it was tested with variety of 
> monitors extensively. So we now read the edid only during init and during hotplug.
> For SKL, the "[PATCH] drm/i915: Handle HPD when it has actually occurred"
> patch makes HPD stable enough.
> So, we can rely on the edid read from init_connector instead of 
> reading edid on every detect call.

Again, not going to take this with random gen checks. I want your fix for handling hpd on other platforms, then roll this out everywhere.
-Daniel
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch