[Intel-gfx] [PATCH] drm/i915: be more careful when returning -ENXIO in gmbus transfer

[Chris Wilson]

On Mon, 21 May 2012 20:19:48 +0200, Daniel Vetter <daniel.vetter at ffwll.ch> wrote:
> ... flaky ddc hardware can cause a spurious NAK, resulting in the i2c
> core and drm edid functions not trying to retry the edid transfer.
> 
> Luckily the gmbus quiescenting also times out for these cases, so we
> can get out of this mess by returning -ETIMEDOUT for this specific
> case. This way we keep the fast-fail of returning -ENXIO if there is
> no device present, speeding up the boot process.
> 
> This regression has been introduced in
> 
> commit e646d5773572bf52017983d758bdf05777dc5600
> Author: Daniel Kurtz <djkurtz at chromium.org>
> Date:   Fri Mar 30 19:46:38 2012 +0800
> 
>     drm/i915/intel_i2c: always wait for IDLE before clearing NAK
> 
> v2: Return -ETIMEDOUT for this case and keep the -ENXIO for real NAKs,
> suggested by Daniel Kurtz.
> 
> Cc: Daniel Kurtz <djkurtz at chromium.org>
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=49518
> Reported-and-Tested-by: Julian Simioni <julian.simioni at gmail.com>
> Signed-Off-by: Daniel Vetter <daniel.vetter at ffwll.ch>

Acked-by: Chris Wilson <chris at chris-wilson.co.uk>
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre