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

From: Jani Nikula <jani.nikula@intel.com>
To: Daniel Vetter <daniel@ffwll.ch>
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 19:40:00 +0300	[thread overview]
Message-ID: <8738fcu3a7.fsf@intel.com> (raw)
In-Reply-To: <20140610072536.GH5821@phenom.ffwll.local>

On Tue, 10 Jun 2014, Daniel Vetter <daniel@ffwll.ch> wrote:
> 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>

With that, pushed to -fixes.

BR,
Jani.

>
>> ---
>>  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
>> 
>> _______________________________________________
>> Intel-gfx mailing list
>> 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

-- 
Jani Nikula, Intel Open Source Technology Center