Re: [PATCH] drm/i915: Set edid from init and not from detect

From: Daniel Vetter <daniel@ffwll.ch>
To: "Sharma, Shashank" <shashank.sharma@intel.com>
Cc: "intel-gfx@lists.freedesktop.org" <intel-gfx@lists.freedesktop.org>
Subject: Re: [PATCH] drm/i915: Set edid from init and not from detect
Date: Tue, 14 Jul 2015 09:59:12 +0200	[thread overview]
Message-ID: <20150714075912.GE3736@phenom.ffwll.local> (raw)
In-Reply-To: <FF3DDC77922A8A4BB08A3BC48A1EA8CB09957FCC@BGSMSX101.gar.corp.intel.com>

On Tue, Jul 14, 2015 at 03:48:36AM +0000, Sharma, Shashank wrote:
> 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. 

I have a gen7 machine here which is currently (and it's somewhat random)
broken wrt hpd and hdmi. And afaics this patch series doesn't have the
bugfix for the hpd handling - or did I miss it?
-Daniel

> 
> Regards
> Shashank
> -----Original Message-----
> From: Daniel Vetter [mailto:daniel.vetter@ffwll.ch] On Behalf Of Daniel Vetter
> Sent: Monday, July 13, 2015 8:27 PM
> To: Jindal, Sonika
> Cc: Chris Wilson; intel-gfx@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

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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