linux-kernel - Re: [PATCH] drm: Reduce the number of retries whilst reading EDIDs

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Date:	Thu, 23 Feb 2012 19:36:41 -0200
From:	Eugeni Dodonov <eugeni.dodonov@...el.com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
CC:	Chris Wilson <chris@...is-wilson.co.uk>,
	linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org,
	Dave Airlie <airlied@...hat.com>,
	Alex Deucher <alexdeucher@...il.com>
Subject: Re: [PATCH] drm: Reduce the number of retries whilst reading EDIDs

On 02/23/2012 06:15 PM, Linus Torvalds wrote:
> On Thu, Feb 23, 2012 at 11:52 AM, Chris Wilson<chris@...is-wilson.co.uk>  wrote:
>>
>> i2c retries if sees an EGAIN, drm_do_probe_ddc_edid retries until it
>> gets a result and *then* drm_do_get_edid retries until it gets a result
>> it is happy with. All in all, that is a lot of processor intensive
>> looping in cases where we do not expect and cannot get valid data - for
>> example on Intel with disconnected hardware we will busy-spin until we
>> hit the i2c timeout. This is then repeated for every connector when
>> querying the current status of outputs.
>
> Sadly, this doesn't seem to make any difference to my case. My xrandr
> stays at 0.555s even with this patch.

Perhaps a stupid question, but does you tree has 
http://cgit.freedesktop.org/~airlied/linux/commit/?h=drm-next&id=9292f37e1f5c79400254dca46f83313488093825 
from Dave's drm-next?

If it has, it would be the 1st time that I see xrandr take longer than 
.5s with that patch on an Intel GPU. We even added a check for this into 
intel-gpu-tools to warn us if any machine takes that long, and none had 
hit it so far. So if this is the case here, there is something Mac 
Mini-specific indeed to investigate.

-Eugeni
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