[Intel-gfx] [PATCH v2] drm/i915: Fix eDP blank screen after S3 resume on HP desktops

[Paul Menzel]

Am Donnerstag, den 21.06.2012, 15:30 +0200 schrieb Takashi Iwai:
> This patch fixes the problem on some HP desktop machines with eDP
> which give blank screens after S3 resume.
> 
> It turned out that BLC_PWM_CPU_CTL must be written after
> BLC_PWM_CPU_CTL2.  Otherwise it doesn't take effect on these
> SNB machines.
> 
> Tested with 3.5-rc3 kernel.
> 
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=49233

Hmm, the bug entry does not contain a link to the discussion on
intel-gfx.

http://lists.freedesktop.org/archives/intel-gfx/2012-June/018418.html

Maybe add it there or to the commit message.

> Cc: <stable at vger.kernel.org>
> Signed-off-by: Takashi Iwai <tiwai at suse.de>
> ---
>  drivers/gpu/drm/i915/i915_suspend.c |    5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_suspend.c b/drivers/gpu/drm/i915/i915_suspend.c
> index 0ede02a..a748e5c 100644
> --- a/drivers/gpu/drm/i915/i915_suspend.c
> +++ b/drivers/gpu/drm/i915/i915_suspend.c
> @@ -740,8 +740,11 @@ static void i915_restore_display(struct drm_device *dev)
>  	if (HAS_PCH_SPLIT(dev)) {
>  		I915_WRITE(BLC_PWM_PCH_CTL1, dev_priv->saveBLC_PWM_CTL);
>  		I915_WRITE(BLC_PWM_PCH_CTL2, dev_priv->saveBLC_PWM_CTL2);
> -		I915_WRITE(BLC_PWM_CPU_CTL, dev_priv->saveBLC_CPU_PWM_CTL);
> +		/* NOTE: BLC_PWM_CPU_CTL must be written after BLC_PWM_CPU_CTL2;
> +		 * otherwise we get blank eDP screen after S3 on some machines

Full stop at the end? Also add a reference to the list discussion or
Bugzilla entry?

> +		 */
>  		I915_WRITE(BLC_PWM_CPU_CTL2, dev_priv->saveBLC_CPU_PWM_CTL2);
> +		I915_WRITE(BLC_PWM_CPU_CTL, dev_priv->saveBLC_CPU_PWM_CTL);
>  		I915_WRITE(PCH_PP_ON_DELAYS, dev_priv->savePP_ON_DELAYS);
>  		I915_WRITE(PCH_PP_OFF_DELAYS, dev_priv->savePP_OFF_DELAYS);
>  		I915_WRITE(PCH_PP_DIVISOR, dev_priv->savePP_DIVISOR);

With or without these changes above, this patch is

Acked-by: Paul Menzel <paulepanter at users.sourceforge.net>


Thanks,

Paul
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