From: Daniel Vetter <daniel.vetter@ffwll.ch>
Date: Thu, 10 May 2012 13:21:57 +0200
Subject: [PATCH] drm/i915: be more careful when returning -ENXIO in gmbus
transfer
... 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@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@chromium.org>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=49518
Reported-and-not-yet-Tested-by: Julian Simioni <julian.simioni@gmail.com>
Signed-Off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
---
drivers/gpu/drm/i915/intel_i2c.c | 21 ++++++++++++---------
1 file changed, 12 insertions(+), 9 deletions(-)