Re: [PATCH for stable 3.14 only 1/1] drm/i915: restore QUIRK_NO_PCH_PWM_ENABLE

[Daniel Vetter <daniel@ffwll.ch>]

On Mon, Apr 28, 2014 at 01:10:07PM +0300, Jani Nikula wrote:
> This reverts the bisected regressing
> 
> commit bc0bb9fd1c7810407ab810d204bbaecb255fddde
> Author: Jani Nikula <jani.nikula@intel.com>
> Date:   Thu Nov 14 12:14:29 2013 +0200
> 
>     drm/i915: remove QUIRK_NO_PCH_PWM_ENABLE
> 
> restoring QUIRK_NO_PCH_PWM_ENABLE for a couple of Dell XPS models which
> broke in 3.14.
> 
> There is no such revert upstream. We have root caused and fixed the
> issue upstream, without the quirk, with:
> 
> commit 39fbc9c8f6765959b55e0b127dd5c57df5a47d67
> Author: Jani Nikula <jani.nikula@intel.com>
> Date:   Wed Apr 9 11:22:06 2014 +0300
> 
>     drm/i915: check VBT for supported backlight type
> 
> and
> 
> commit c675949ec58ca50d5a3ae3c757892f1560f6e896
> Author: Jani Nikula <jani.nikula@intel.com>
> Date:   Wed Apr 9 11:31:37 2014 +0300
> 
>     drm/i915: do not setup backlight if not available according to VBT
> 
> While the commits are within the stable rules otherwise, and fix more
> machines than just the regressed Dell XPS models, we feel backporting
> them to stable may be too risky. The revert is limited to the broken
> machines, and the impact should be effectively the same as what the
> upstream commits do more generally.
> 
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=76276
> Reported-by: Romain Francoise <romain@orebokech.com>
> CC: Kamal Mostafa <kamal@canonical.com>
> CC: Daniel Vetter <daniel@ffwll.ch>
> CC: stable@vger.kernel.org (3.14 only)
> Signed-off-by: Jani Nikula <jani.nikula@intel.com>

Ack from my side since the VBT-based fix we have in 3.15 really is a bit
too risky for backporting and should get the full -rc cycle for testing.
But we just can't let existing users on affected hw hang in there for 2
months.
-Daniel

> ---
>  drivers/gpu/drm/i915/i915_drv.h      |  1 +
>  drivers/gpu/drm/i915/intel_display.c | 16 ++++++++++++++++
>  drivers/gpu/drm/i915/intel_panel.c   |  4 ++++
>  3 files changed, 21 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
> index df77e20e3c3d..697f2150a997 100644
> --- a/drivers/gpu/drm/i915/i915_drv.h
> +++ b/drivers/gpu/drm/i915/i915_drv.h
> @@ -734,6 +734,7 @@ 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 9b8a7c7ea7fc..963639d9049b 100644
> --- a/drivers/gpu/drm/i915/intel_display.c
> +++ b/drivers/gpu/drm/i915/intel_display.c
> @@ -10771,6 +10771,17 @@ 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;
> @@ -10839,6 +10850,11 @@ 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 079ea38f14d9..9f1d7a9300e8 100644
> --- a/drivers/gpu/drm/i915/intel_panel.c
> +++ b/drivers/gpu/drm/i915/intel_panel.c
> @@ -671,6 +671,10 @@ static void pch_enable_backlight(struct intel_connector *connector)
>  	pch_ctl2 = panel->backlight.max << 16;
>  	I915_WRITE(BLC_PWM_PCH_CTL2, pch_ctl2);
>  
> +	/* XXX: transitional */
> +	if (dev_priv->quirks & QUIRK_NO_PCH_PWM_ENABLE)
> +		return;
> +
>  	pch_ctl1 = 0;
>  	if (panel->backlight.active_low_pwm)
>  		pch_ctl1 |= BLM_PCH_POLARITY;
> -- 
> 1.9.1
> 

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