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

From: Linus Torvalds
Date: Thu Feb 23 2012 - 15:36:49 EST


On Thu, Feb 23, 2012 at 12:15 PM, Linus Torvalds
<torvalds@xxxxxxxxxxxxxxxxxxxx> 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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