Re: [PATCH] drm/i915: bdw does not have pch backlight override bit

From: "Ville Syrjälä" <ville.syrjala@linux.intel.com>
To: Jani Nikula <jani.nikula@intel.com>
Cc: intel-gfx@lists.freedesktop.org
Subject: Re: [PATCH] drm/i915: bdw does not have pch backlight override bit
Date: Thu, 4 Sep 2014 16:07:32 +0300	[thread overview]
Message-ID: <20140904130732.GH4193@intel.com> (raw)
In-Reply-To: <87y4tzefmz.fsf@intel.com>

On Thu, Sep 04, 2014 at 03:25:56PM +0300, Jani Nikula wrote:
> On Thu, 04 Sep 2014, Ville Syrjälä <ville.syrjala@linux.intel.com> wrote:
> > On Thu, Sep 04, 2014 at 02:56:09PM +0300, Jani Nikula wrote:
> >> BDW is always in the PCH override mode, and the bit MBZ.
> >
> > BSpec doesn't seem to agree. In fact it says the override must be
> > enabled on bdw.
> 
> Gah, I was looking at the skl bspec, which said bdw+. Oh well, how about
> this one instead:
> 
> 
> >From 53db5d77cf8e959ed65535f2d80f721baf74d93a Mon Sep 17 00:00:00 2001
> From: Jani Nikula <jani.nikula@intel.com>
> Date: Thu, 4 Sep 2014 14:54:34 +0300
> Subject: [PATCH] drm/i915: skl does not have pch backlight override bit
> Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo
> Cc: Jani Nikula <jani.nikula@intel.com>
> 
> SKL is always in the PCH override mode, and the bit MBZ.
> 
> Signed-off-by: Jani Nikula <jani.nikula@intel.com>
> ---
>  drivers/gpu/drm/i915/intel_panel.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_panel.c b/drivers/gpu/drm/i915/intel_panel.c
> index 18784470a760..bc3e74eaf52e 100644
> --- a/drivers/gpu/drm/i915/intel_panel.c
> +++ b/drivers/gpu/drm/i915/intel_panel.c
> @@ -781,7 +781,8 @@ static void bdw_enable_backlight(struct intel_connector *connector)
>  		pch_ctl1 |= BLM_PCH_POLARITY;
>  
>  	/* BDW always uses the pch pwm controls. */
> -	pch_ctl1 |= BLM_PCH_OVERRIDE_ENABLE;
> +	if (IS_BROADWELL(dev))
> +		pch_ctl1 |= BLM_PCH_OVERRIDE_ENABLE;

I guess this should really check for the PCH version instead. I'm
slightly concerned about early SKLs being equipped with WPT where
this might cause problems.

>  
>  	I915_WRITE(BLC_PWM_PCH_CTL1, pch_ctl1);
>  	POSTING_READ(BLC_PWM_PCH_CTL1);
> -- 
> 1.9.1
> 
> 
> 
> 
> >
> >> 
> >> Signed-off-by: Jani Nikula <jani.nikula@intel.com>
> >> ---
> >>  drivers/gpu/drm/i915/intel_panel.c | 3 ---
> >>  1 file changed, 3 deletions(-)
> >> 
> >> diff --git a/drivers/gpu/drm/i915/intel_panel.c b/drivers/gpu/drm/i915/intel_panel.c
> >> index 18784470a760..066a66165cf1 100644
> >> --- a/drivers/gpu/drm/i915/intel_panel.c
> >> +++ b/drivers/gpu/drm/i915/intel_panel.c
> >> @@ -780,9 +780,6 @@ static void bdw_enable_backlight(struct intel_connector *connector)
> >>  	if (panel->backlight.active_low_pwm)
> >>  		pch_ctl1 |= BLM_PCH_POLARITY;
> >>  
> >> -	/* BDW always uses the pch pwm controls. */
> >> -	pch_ctl1 |= BLM_PCH_OVERRIDE_ENABLE;
> >> -
> >>  	I915_WRITE(BLC_PWM_PCH_CTL1, pch_ctl1);
> >>  	POSTING_READ(BLC_PWM_PCH_CTL1);
> >>  	I915_WRITE(BLC_PWM_PCH_CTL1, pch_ctl1 | BLM_PCH_PWM_ENABLE);
> >> -- 
> >> 1.9.1
> >> 
> >> _______________________________________________
> >> Intel-gfx mailing list
> >> Intel-gfx@lists.freedesktop.org
> >> http://lists.freedesktop.org/mailman/listinfo/intel-gfx
> >
> > -- 
> > Ville Syrjälä
> > Intel OTC
> 
> -- 
> Jani Nikula, Intel Open Source Technology Center

-- 
Ville Syrjälä
Intel OTC