Re: [PATCH 3/4] drm/i915: add quirk to indicate that an alt bit is used for brightness inversion

Daniel Vetter
2012-04-26T17:07:48Z

On Thu, Apr 26, 2012 at 06:48:36PM +0200, Carsten Emde wrote:
> Bit #28 of the backlight control BLC_PWM_CTL2 is normally used
> to indicate whether the brightness of the panel backlight is
> inverted. Sometimes, however, bit #29 is used for this purpose.
> Add a quirk to mark machines that do so.
>
> Signed-off-by: Carsten Emde <C.Emde@osadl.org>
>
> ---
> drivers/gpu/drm/i915/i915_drv.h | 1 +
> drivers/gpu/drm/i915/i915_reg.h | 1 +
> drivers/gpu/drm/i915/intel_display.c | 10 ++++++++++
> drivers/gpu/drm/i915/intel_panel.c | 12 ++++++++++--
> 4 files changed, 22 insertions(+), 2 deletions(-)
>
> Index: linux-tip/drivers/gpu/drm/i915/i915_drv.h
> ===================================================================
> --- linux-tip.orig/drivers/gpu/drm/i915/i915_drv.h
> +++ linux-tip/drivers/gpu/drm/i915/i915_drv.h
> @@ -295,6 +295,7 @@ enum intel_pch {
>
> #define QUIRK_PIPEA_FORCE (1<<0)
> #define QUIRK_LVDS_SSC_DISABLE (1<<1)
> +#define QUIRK_ALT_BIT_FOR_BRIGHTNESS_INVERSION (2<<1)
>
> struct intel_fbdev;
> struct intel_fbc_work;
> Index: linux-tip/drivers/gpu/drm/i915/i915_reg.h
> ===================================================================
> --- linux-tip.orig/drivers/gpu/drm/i915/i915_reg.h
> +++ linux-tip/drivers/gpu/drm/i915/i915_reg.h
> @@ -1685,6 +1685,7 @@
> /* Backlight control */
> #define BLC_PWM_CTL2 0x61250 /* 965+ only */
> #define BLM_COMBINATION_MODE (1 << 30)
> +#define BLM_ALT_POLARITY_I965 (1 << 29) /* quirk only */

bit29 is the pipe select bit, i.e. the backlight controller uses the pixel
clock from this pipe as the signal to module the backlight.

I need to look some more into this.
-Daniel

> #define BLM_POLARITY_I965 (1 << 28) /* gen4 only */
> #define BLC_PWM_CTL 0x61254
> /*
> Index: linux-tip/drivers/gpu/drm/i915/intel_display.c
> ===================================================================
> --- linux-tip.orig/drivers/gpu/drm/i915/intel_display.c
> +++ linux-tip/drivers/gpu/drm/i915/intel_display.c
> @@ -9101,6 +9101,16 @@ static void quirk_ssc_force_disable(stru
> dev_priv->quirks |= QUIRK_LVDS_SSC_DISABLE;
> }
>
> +/*
> + * A machine may use an alternate bit to indicate panel backlight brightness
> + * inversion
> + */
> +static void quirk_alt_bit_for_brightness_inversion(struct drm_device *dev)
> +{
> + struct drm_i915_private *dev_priv = dev->dev_private;
> + dev_priv->quirks |= QUIRK_ALT_BIT_FOR_BRIGHTNESS_INVERSION;
> +}
> +
> struct intel_quirk {
> int device;
> int subsystem_vendor;
> Index: linux-tip/drivers/gpu/drm/i915/intel_panel.c
> ===================================================================
> --- linux-tip.orig/drivers/gpu/drm/i915/intel_panel.c
> +++ linux-tip/drivers/gpu/drm/i915/intel_panel.c
> @@ -208,9 +208,17 @@ static u32 intel_panel_compute_brightnes
> 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))
> + if (IS_GEN4(dev)) {
> + /* gen4 has a - possibly quirked - polarity bit */
> + int mask;
> +
> + if (dev_priv->quirks & QUIRK_ALT_BIT_FOR_BRIGHTNESS_INVERSION)
> + mask = BLM_ALT_POLARITY_I965;
> + else
> + mask = BLM_POLARITY_I965;
> + if (I915_READ(BLC_PWM_CTL2) & mask)
> return intel_panel_get_max_backlight(dev) - val;
> + }
>
> return val;
> }
>

--
Daniel Vetter
Mail: daniel@ffwll.ch
Mobile: +41 (0)79 365 57 48