Re: [PATCH 2/2] drm/i915: pnv has a backlight polarity control bit, too

[Chris Wilson <chris@chris-wilson.co.uk>]

On Mon, 23 Apr 2012 11:32:15 +0200, Daniel Vetter <daniel.vetter@ffwll.ch> wrote:
> So let's use it.
> 
> We already correctly ignore bit0 on gen < 4, now we also now why ;-)
> I've decided that losing that single bit of precision isn't worth the
> trouble to sprinkle IS_PINEVIEW checks all over the backlight control
> code - that code is way too fragile imo.
> 
> Cc: Chris Wilson <chris@chris-wilson.co.uk>
> Signed-Off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
> ---
>  drivers/gpu/drm/i915/i915_reg.h    |    2 ++
>  drivers/gpu/drm/i915/intel_panel.c |    5 +++--
>  2 files changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
> index 67c4ca0..45d5568 100644
> --- a/drivers/gpu/drm/i915/i915_reg.h
> +++ b/drivers/gpu/drm/i915/i915_reg.h
> @@ -1805,6 +1805,8 @@
>   */
>  #define   BACKLIGHT_DUTY_CYCLE_SHIFT		(0)
>  #define   BACKLIGHT_DUTY_CYCLE_MASK		(0xffff)
> +#define   BACKLIGHT_DUTY_CYCLE_MASK_PNV		(0xfffe)
> +#define   BLM_POLARITY_PNV			(1 << 0) /* pnv only */
>  
>  #define BLC_HIST_CTL		0x61260
>  
> diff --git a/drivers/gpu/drm/i915/intel_panel.c b/drivers/gpu/drm/i915/intel_panel.c
> index 1874517..e519221 100644
> --- a/drivers/gpu/drm/i915/intel_panel.c
> +++ b/drivers/gpu/drm/i915/intel_panel.c
> @@ -212,8 +212,9 @@ static u32 intel_panel_compute_brightness(struct drm_device *dev, u32 val)
>  	    dev_priv->quirks & QUIRK_INVERT_BRIGHTNESS)
>  		return intel_panel_get_max_backlight(dev) - val;
>  
> -	/* gen4 has a polarity bit */
> -	if (IS_GEN4(dev) && (I915_READ(BLC_PWM_CTL2) & BLM_POLARITY_I965))
> +	/* gen4/pnv has a polarity bit */
> +	if (IS_GEN4(dev) && (I915_READ(BLC_PWM_CTL2) & BLM_POLARITY_I965) ||
> +	    IS_PINEVIEW(dev) && (I915_READ(BLC_PWM_CTL) & BLM_POLARITY_PNV))

Now that is just getting ugly. Break this out into a simple and readable
predicate function intel_panel_backlight_is_inverted().

>  			return intel_panel_get_max_backlight(dev) - val;
Tabtastic.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre