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

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Date:	Thu, 23 Feb 2012 12:36:30 -0800
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Chris Wilson <chris@...is-wilson.co.uk>
Cc:	linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org,
	Eugeni Dodonov <eugeni.dodonov@...el.com>,
	Dave Airlie <airlied@...hat.com>,
	Alex Deucher <alexdeucher@...il.com>
Subject: Re: [PATCH] drm: Reduce the number of retries whilst reading EDIDs

On Thu, Feb 23, 2012 at 12:15 PM, Linus Torvalds
<torvalds@...ux-foundation.org> wrote:
>
> Sadly, this doesn't seem to make any difference to my case. My xrandr
> stays at 0.555s even with this patch.

Btw, profiling with call chains seems to say that it all comes from
intel_sdvo_get_analog_edid() (about half from  intel_sdvo_get_modes()
and half from intel_sdvo_tmds_sink_detect()).

All called through drm_ioctl() -> drm_mode_getconnector() ->
drm_helper_probe_single_connector_modes().

Which I guess isn't anything interesting, but that
intel_sdvo_get_analog_edid() thing seems to be very much a Mac mini
hack. There's a comment about that in the sources too:

        /*
         * Mac mini hack.  On this device, the DVI-I connector shares one DDC
         * link between analog and digital outputs. So, if the regular SDVO
         * DDC fails, check to see if the analog output is disconnected, in
         * which case we'll look there for the digital DDC data.
         */

and maybe that mac mini hack ends up interacting badly with something
else? I'll happily test patches if people have any ideas.

                  Linus
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