Re: [PATCH] drm/i915: set backlight duty cycle after backlight enable for gen4

From: Daniel Vetter <daniel@ffwll.ch>
To: Jani Nikula <jani.nikula@intel.com>
Cc: intel-gfx@lists.freedesktop.org, Stable <stable@vger.kernel.org>,
	Marc Milgram <mmilgram@redhat.com>,
	mcy@lm7.fr
Subject: Re: [PATCH] drm/i915: set backlight duty cycle after backlight enable for gen4
Date: Tue, 10 Jun 2014 09:25:36 +0200	[thread overview]
Message-ID: <20140610072536.GH5821@phenom.ffwll.local> (raw)
In-Reply-To: <1402327474-27930-1-git-send-email-jani.nikula@intel.com>

On Mon, Jun 09, 2014 at 06:24:34PM +0300, Jani Nikula wrote:
> For reasons I can't claim to fully understand gen4 seems to require
> backlight duty cycle setting after the backlight has been enabled, or
> else black screen follows. I don't have documentation for the correct
> sequence on gen4 either. Confirmed on Dell Latitude D630 and MacBook4,1.
> 
> This fixes a regression introduced by
> commit b35684b8fa94e04f55fd38bf672b737741d2f9e2
> Author: Jani Nikula <jani.nikula@intel.com>
> Date:   Thu Nov 14 12:13:41 2013 +0200
> 
>     drm/i915: do full backlight setup at enable time
> 
> Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=75791
> Reported-and-tested-by: mcy@lm7.fr
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=79423
> Reported-and-tested-by: Marc Milgram <mmilgram@redhat.com>
> Cc: Stable <stable@vger.kernel.org> # 3.14+
> Signed-off-by: Jani Nikula <jani.nikula@intel.com>

Yeah, docs don't mention anything. But if it works it's fine, so
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>

> ---
>  drivers/gpu/drm/i915/intel_panel.c | 5 ++---
>  1 file changed, 2 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_panel.c b/drivers/gpu/drm/i915/intel_panel.c
> index 5e6c888b4928..38a98570d10c 100644
> --- a/drivers/gpu/drm/i915/intel_panel.c
> +++ b/drivers/gpu/drm/i915/intel_panel.c
> @@ -798,9 +798,6 @@ static void i965_enable_backlight(struct intel_connector *connector)
>  	ctl = freq << 16;
>  	I915_WRITE(BLC_PWM_CTL, ctl);
>  
> -	/* XXX: combine this into above write? */
> -	intel_panel_actually_set_backlight(connector, panel->backlight.level);
> -
>  	ctl2 = BLM_PIPE(pipe);
>  	if (panel->backlight.combination_mode)
>  		ctl2 |= BLM_COMBINATION_MODE;
> @@ -809,6 +806,8 @@ static void i965_enable_backlight(struct intel_connector *connector)
>  	I915_WRITE(BLC_PWM_CTL2, ctl2);
>  	POSTING_READ(BLC_PWM_CTL2);
>  	I915_WRITE(BLC_PWM_CTL2, ctl2 | BLM_PWM_ENABLE);
> +
> +	intel_panel_actually_set_backlight(connector, panel->backlight.level);
>  }
>  
>  static void vlv_enable_backlight(struct intel_connector *connector)
> -- 
> 1.9.1
> 
> _______________________________________________
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> Intel-gfx@lists.freedesktop.org
> http://lists.freedesktop.org/mailman/listinfo/intel-gfx

-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch