linux-kernel - Re: [PATCH] drm/i915: quirk no PCH_PWM

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Message-ID: <20130720085339.GS5615@phenom.ffwll.local>
Date:	Sat, 20 Jul 2013 10:53:39 +0200
From:	Daniel Vetter <daniel@...ll.ch>
To:	Kamal Mostafa <kamal@...onical.com>
Cc:	Daniel Vetter <daniel.vetter@...ll.ch>,
	David Airlie <airlied@...ux.ie>,
	intel-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drm/i915: quirk no PCH_PWM_ENABLE for Dell XPS13
 backlight

On Fri, Jul 19, 2013 at 03:02:01PM -0700, Kamal Mostafa wrote:
> BugLink: https://bugzilla.kernel.org/show_bug.cgi?id=47941
> BugLink: https://bugs.launchpad.net/bugs/1163720
> BugLink: https://bugs.launchpad.net/bugs/1162026
> 
> Some machines suffer from non-functional backlight controls if
> BLM_PCH_PWM_ENABLE is set, so provide a quirk to avoid doing so.
> Apply this quirk to Dell XPS 13 models.
> 
> Tested-by: Eric Griffith <EGriffith92@...il.com>
> Tested-by: Kent Baxley <kent.baxley@...onical.com>
> Cc: <stable@...r.kernel.org> # v3.8+
> Signed-off-by: Kamal Mostafa <kamal@...onical.com>

I still wonder what exactly's going on here, but for backlight stuff I've
given up on avoiding quirks ;-) Thanks for digging into this, patch
applied to -fixes.
-Daniel

> ---
>  drivers/gpu/drm/i915/i915_drv.h      |  1 +
>  drivers/gpu/drm/i915/intel_display.c | 16 ++++++++++++++++
>  drivers/gpu/drm/i915/intel_panel.c   |  3 ++-
>  3 files changed, 19 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
> index a416645..204c3ec 100644
> --- a/drivers/gpu/drm/i915/i915_drv.h
> +++ b/drivers/gpu/drm/i915/i915_drv.h
> @@ -555,6 +555,7 @@ enum intel_sbi_destination {
>  #define QUIRK_PIPEA_FORCE (1<<0)
>  #define QUIRK_LVDS_SSC_DISABLE (1<<1)
>  #define QUIRK_INVERT_BRIGHTNESS (1<<2)
> +#define QUIRK_NO_PCH_PWM_ENABLE (1<<3)
>  
>  struct intel_fbdev;
>  struct intel_fbc_work;
> diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
> index 85f3eb7..42e207e 100644
> --- a/drivers/gpu/drm/i915/intel_display.c
> +++ b/drivers/gpu/drm/i915/intel_display.c
> @@ -9398,6 +9398,17 @@ static void quirk_invert_brightness(struct drm_device *dev)
>  	DRM_INFO("applying inverted panel brightness quirk\n");
>  }
>  
> +/*
> + * Some machines (Dell XPS13) suffer broken backlight controls if
> + * BLM_PCH_PWM_ENABLE is set.
> + */
> +static void quirk_no_pcm_pwm_enable(struct drm_device *dev)
> +{
> +	struct drm_i915_private *dev_priv = dev->dev_private;
> +	dev_priv->quirks |= QUIRK_NO_PCH_PWM_ENABLE;
> +	DRM_INFO("applying no-PCH_PWM_ENABLE quirk\n");
> +}
> +
>  struct intel_quirk {
>  	int device;
>  	int subsystem_vendor;
> @@ -9467,6 +9478,11 @@ static struct intel_quirk intel_quirks[] = {
>  
>  	/* Acer Aspire 4736Z */
>  	{ 0x2a42, 0x1025, 0x0260, quirk_invert_brightness },
> +
> +	/* Dell XPS13 HD Sandy Bridge */
> +	{ 0x0116, 0x1028, 0x052e, quirk_no_pcm_pwm_enable },
> +	/* Dell XPS13 HD and XPS13 FHD Ivy Bridge */
> +	{ 0x0166, 0x1028, 0x058b, quirk_no_pcm_pwm_enable },
>  };
>  
>  static void intel_init_quirks(struct drm_device *dev)
> diff --git a/drivers/gpu/drm/i915/intel_panel.c b/drivers/gpu/drm/i915/intel_panel.c
> index 80bea1d..01b5a51 100644
> --- a/drivers/gpu/drm/i915/intel_panel.c
> +++ b/drivers/gpu/drm/i915/intel_panel.c
> @@ -580,7 +580,8 @@ void intel_panel_enable_backlight(struct drm_device *dev,
>  		POSTING_READ(reg);
>  		I915_WRITE(reg, tmp | BLM_PWM_ENABLE);
>  
> -		if (HAS_PCH_SPLIT(dev)) {
> +		if (HAS_PCH_SPLIT(dev) &&
> +		    !(dev_priv->quirks & QUIRK_NO_PCH_PWM_ENABLE)) {
>  			tmp = I915_READ(BLC_PWM_PCH_CTL1);
>  			tmp |= BLM_PCH_PWM_ENABLE;
>  			tmp &= ~BLM_PCH_OVERRIDE_ENABLE;
> -- 
> 1.8.1.2
> 

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