linux-kernel - [bisected] drm/ksm: fbdev blanking regression in 2.6.33

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Date:	Wed,  6 Jan 2010 18:00:25 +0100
From:	Johan Hovold <jhovold@...il.com>
To:	Dave Airlie <airlied@...hat.com>
Cc:	James Simmons <jsimmons@...radead.org>,
	dri-devel@...ts.sourceforge.net, linux-kernel@...r.kernel.org
Subject: [bisected] drm/ksm: fbdev blanking regression in 2.6.33

Hi,

Console blanking broke on my laptop with GM45 chipset with 2.6.33. Instead of
blanking, the screen was dimmed and the backlight started glowing in the lower
edges of the screen. The glowing then slowly spread upwards. Did not look
healthy at all.

Easily reproduced by issuing "setterm -blank force".

I bisected it down to 731b5a15a3b1474a41c2ca29b4c32b0f21bc852e (drm/kms:
properly handle fbdev blanking). Which instead of going directly to
DPMS_STANDBY now calls the encoder dpms helper with DRM_MODE_DPMS_ON and the
crtc dpms helper with DRM_MODE_DPMS_OFF. I've verified that is this combination
that triggers the bug. 

If I don't call crtc_funcs->dpms(crtc, DRM_MODE_DPMS_OFF) on FB_BLANK_NORMAL
but still encoder_funcs->dpms(encoder, DRM_MODE_DPMS_ON), the bug is not
triggered, but the screen is not cleared either.

For now, I simply reverted to the old behaviour of going directly to
DPMS_STANDBY (see follow-up patch).  

Thanks,
Johan

Johan Hovold (1):
  drm/kms: fix fbdev blanking regression

 drivers/gpu/drm/drm_fb_helper.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

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