Date:	Thu, 25 Jul 2013 07:43:17 -0700
From:	Kamal Mostafa <kamal@...onical.com>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
Cc:	James Hogan <james@...anarts.com>, Aaron Lu <aaron.lu@...el.com>,
	Kalle Valo <kvalo@...rom.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Matthew Garrett <matthew.garrett@...ula.com>,
	"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
	Steven Newbury <steve@...wbury.org.uk>,
	ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
	Jörg Otte <jrg.otte@...il.com>,
	Martin Steigerwald <Martin@...htvoll.de>,
	Daniel Vetter <daniel.vetter@...ll.ch>,
	intel-gfx <intel-gfx@...ts.freedesktop.org>,
	Jani Nikula <jani.nikula@...ux.intel.com>
Subject: Re: Linux 3.11-rc2 (acpi backlight, revert)

On Thu, 2013-07-25 at 15:00 +0200, Rafael J. Wysocki wrote:
> On Monday, July 22, 2013 09:54:21 PM Rafael J. Wysocki wrote:
> > On Monday, July 22, 2013 11:11:54 AM Linus Torvalds wrote:
> > > On Mon, Jul 22, 2013 at 6:02 AM, Rafael J. Wysocki <rjw@...k.pl> wrote:
> > > >
> > > > Linus, do you want me to send a pull request reverting 8c5bd7a and efaa14c?
> > > 
> > > Yes, but let's wait a while. Not because I think we'll fix the problem
> > > (hey, miracles might happen), but because I think it would be useful
> > > to couple the reverts with information about the particular machines
> > > that broke (and the people who reported it). So that when we
> > > inevitably try again, we can perhaps get some testing effort with
> > > those machines/people.
> > > 
> > > It doesn't seem to be a show-stopped for a large number of people, so
> > > there's no huge hurry. I'd suggest doing the revert just in time for
> > > rc3, but waiting until then to gather info about people who see
> > > breakage.
> > > 
> > > Sound like a plan?
> > 
> > Yes, it does.
> 
> OK, time to revert I guess.
> 
> James, Kamal, Steven, Jörg, Martin, Kalle, please check if the apppended patch
> fixes the backlight for you.

Yes, this revert patch does re-enable backlight control for the affected
Dell XPS13 models.

 -Kamal


> Aaron, please double check if acpi_video_backlight_quirks() will still work as
> needed.
> 
> Thanks,
> Rafael
> 
> 
> ---
> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> Subject: Revert "ACPI / video / i915: No ACPI backlight if firmware expects Windows 8"
> 
> We attempted to address a regression introduced by commit a57f7f9
> (ACPICA: Add Windows8/Server2012 string for _OSI method.) after which
> ACPI video backlight support doesn't work on a number of systems,
> because the relevant AML methods in the ACPI tables in their BIOSes
> become useless after the BIOS has been told that the OS is compatible
> with Windows 8.  That problem is tracked by the bug entry at:
> 
> https://bugzilla.kernel.org/show_bug.cgi?id=51231
> 
> Commit 8c5bd7a (ACPI / video / i915: No ACPI backlight if firmware
> expects Windows 8) introduced for this purpose essentially prevented
> the ACPI backlight support from being used if the BIOS had been told
> that the OS was compatible with Windows 8 and the i915 driver was
> loaded, in which case the backlight would always be handled by i915.
> Unfortunately, however, that turned out to cause problems with
> backlight to appear on multiple systems with symptoms indicating that
> i915 was unable to control the backlight on those systems as
> expected.
> 
> For this reason, revert commit 8c5bd7a, but leave the function
> acpi_video_backlight_quirks() introduced by it, because another
> commit on top of it uses that function.
> 
> References: https://lkml.org/lkml/2013/7/21/119
> References: https://lkml.org/lkml/2013/7/22/261
> References: https://lkml.org/lkml/2013/7/23/429
> References: https://lkml.org/lkml/2013/7/23/459
> References: https://lkml.org/lkml/2013/7/23/81
> References: https://lkml.org/lkml/2013/7/24/27
> Reported-by: James Hogan <james@...anarts.com>
> Reported-by: Steven Newbury <steve@...wbury.org.uk>
> Reported-by: Kamal Mostafa <kamal@...onical.com>
> Reported-by: Martin Steigerwald <Martin@...htvoll.de>
> Reported-by: Jörg Otte <jrg.otte@...il.com>
> Reported-by: Kalle Valo <kvalo@...rom.com>
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> ---
>  drivers/acpi/internal.h         |    2 -
>  drivers/acpi/video.c            |   67 ++++------------------------------------
>  drivers/acpi/video_detect.c     |   15 --------
>  drivers/gpu/drm/i915/i915_dma.c |    2 -
>  include/acpi/video.h            |   11 ------
>  include/linux/acpi.h            |    1 
>  6 files changed, 11 insertions(+), 87 deletions(-)
> 
> Index: linux-pm/drivers/acpi/video.c
> ===================================================================
> --- linux-pm.orig/drivers/acpi/video.c
> +++ linux-pm/drivers/acpi/video.c
> @@ -897,7 +897,7 @@ static void acpi_video_device_find_cap(s
>  	if (acpi_video_init_brightness(device))
>  		return;
>  
> -	if (acpi_video_verify_backlight_support()) {
> +	if (acpi_video_backlight_support()) {
>  		struct backlight_properties props;
>  		struct pci_dev *pdev;
>  		acpi_handle acpi_parent;
> @@ -1344,8 +1344,8 @@ acpi_video_switch_brightness(struct acpi
>  	unsigned long long level_current, level_next;
>  	int result = -EINVAL;
>  
> -	/* no warning message if acpi_backlight=vendor or a quirk is used */
> -	if (!acpi_video_verify_backlight_support())
> +	/* no warning message if acpi_backlight=vendor is used */
> +	if (!acpi_video_backlight_support())
>  		return 0;
>  
>  	if (!device->brightness)
> @@ -1843,46 +1843,6 @@ static int acpi_video_bus_remove(struct
>  	return 0;
>  }
>  
> -static acpi_status video_unregister_backlight(acpi_handle handle, u32 lvl,
> -					      void *context, void **rv)
> -{
> -	struct acpi_device *acpi_dev;
> -	struct acpi_video_bus *video;
> -	struct acpi_video_device *dev, *next;
> -
> -	if (acpi_bus_get_device(handle, &acpi_dev))
> -		return AE_OK;
> -
> -	if (acpi_match_device_ids(acpi_dev, video_device_ids))
> -		return AE_OK;
> -
> -	video = acpi_driver_data(acpi_dev);
> -	if (!video)
> -		return AE_OK;
> -
> -	acpi_video_bus_stop_devices(video);
> -	mutex_lock(&video->device_list_lock);
> -	list_for_each_entry_safe(dev, next, &video->video_device_list, entry) {
> -		if (dev->backlight) {
> -			backlight_device_unregister(dev->backlight);
> -			dev->backlight = NULL;
> -			kfree(dev->brightness->levels);
> -			kfree(dev->brightness);
> -		}
> -		if (dev->cooling_dev) {
> -			sysfs_remove_link(&dev->dev->dev.kobj,
> -					  "thermal_cooling");
> -			sysfs_remove_link(&dev->cooling_dev->device.kobj,
> -					  "device");
> -			thermal_cooling_device_unregister(dev->cooling_dev);
> -			dev->cooling_dev = NULL;
> -		}
> -	}
> -	mutex_unlock(&video->device_list_lock);
> -	acpi_video_bus_start_devices(video);
> -	return AE_OK;
> -}
> -
>  static int __init is_i740(struct pci_dev *dev)
>  {
>  	if (dev->device == 0x00D1)
> @@ -1914,25 +1874,14 @@ static int __init intel_opregion_present
>  	return opregion;
>  }
>  
> -int __acpi_video_register(bool backlight_quirks)
> +int acpi_video_register(void)
>  {
> -	bool no_backlight;
> -	int result;
> -
> -	no_backlight = backlight_quirks ? acpi_video_backlight_quirks() : false;
> -
> +	int result = 0;
>  	if (register_count) {
>  		/*
> -		 * If acpi_video_register() has been called already, don't try
> -		 * to register acpi_video_bus, but unregister backlight devices
> -		 * if no backlight support is requested.
> +		 * if the function of acpi_video_register is already called,
> +		 * don't register the acpi_vide_bus again and return no error.
>  		 */
> -		if (no_backlight)
> -			acpi_walk_namespace(ACPI_TYPE_DEVICE, ACPI_ROOT_OBJECT,
> -					    ACPI_UINT32_MAX,
> -					    video_unregister_backlight,
> -					    NULL, NULL, NULL);
> -
>  		return 0;
>  	}
>  
> @@ -1948,7 +1897,7 @@ int __acpi_video_register(bool backlight
>  
>  	return 0;
>  }
> -EXPORT_SYMBOL(__acpi_video_register);
> +EXPORT_SYMBOL(acpi_video_register);
>  
>  void acpi_video_unregister(void)
>  {
> Index: linux-pm/drivers/gpu/drm/i915/i915_dma.c
> ===================================================================
> --- linux-pm.orig/drivers/gpu/drm/i915/i915_dma.c
> +++ linux-pm/drivers/gpu/drm/i915/i915_dma.c
> @@ -1648,7 +1648,7 @@ int i915_driver_load(struct drm_device *
>  	if (INTEL_INFO(dev)->num_pipes) {
>  		/* Must be done after probing outputs */
>  		intel_opregion_init(dev);
> -		acpi_video_register_with_quirks();
> +		acpi_video_register();
>  	}
>  
>  	if (IS_GEN5(dev))
> Index: linux-pm/include/acpi/video.h
> ===================================================================
> --- linux-pm.orig/include/acpi/video.h
> +++ linux-pm/include/acpi/video.h
> @@ -17,21 +17,12 @@ struct acpi_device;
>  #define ACPI_VIDEO_DISPLAY_LEGACY_TV      0x0200
>  
>  #if (defined CONFIG_ACPI_VIDEO || defined CONFIG_ACPI_VIDEO_MODULE)
> -extern int __acpi_video_register(bool backlight_quirks);
> -static inline int acpi_video_register(void)
> -{
> -	return __acpi_video_register(false);
> -}
> -static inline int acpi_video_register_with_quirks(void)
> -{
> -	return __acpi_video_register(true);
> -}
> +extern int acpi_video_register(void);
>  extern void acpi_video_unregister(void);
>  extern int acpi_video_get_edid(struct acpi_device *device, int type,
>  			       int device_id, void **edid);
>  #else
>  static inline int acpi_video_register(void) { return 0; }
> -static inline int acpi_video_register_with_quirks(void) { return 0; }
>  static inline void acpi_video_unregister(void) { return; }
>  static inline int acpi_video_get_edid(struct acpi_device *device, int type,
>  				      int device_id, void **edid)
> Index: linux-pm/drivers/acpi/video_detect.c
> ===================================================================
> --- linux-pm.orig/drivers/acpi/video_detect.c
> +++ linux-pm/drivers/acpi/video_detect.c
> @@ -235,12 +235,7 @@ static void acpi_video_caps_check(void)
>  
>  bool acpi_video_backlight_quirks(void)
>  {
> -	if (acpi_gbl_osi_data >= ACPI_OSI_WIN_8) {
> -		acpi_video_caps_check();
> -		acpi_video_support |= ACPI_VIDEO_SKIP_BACKLIGHT;
> -		return true;
> -	}
> -	return false;
> +	return acpi_gbl_osi_data >= ACPI_OSI_WIN_8;
>  }
>  EXPORT_SYMBOL(acpi_video_backlight_quirks);
>  
> @@ -288,14 +283,6 @@ int acpi_video_backlight_support(void)
>  }
>  EXPORT_SYMBOL(acpi_video_backlight_support);
>  
> -/* For the ACPI video driver use only. */
> -bool acpi_video_verify_backlight_support(void)
> -{
> -	return (acpi_video_support & ACPI_VIDEO_SKIP_BACKLIGHT) ?
> -		false : acpi_video_backlight_support();
> -}
> -EXPORT_SYMBOL(acpi_video_verify_backlight_support);
> -
>  /*
>   * Use acpi_backlight=vendor/video to force that backlight switching
>   * is processed by vendor specific acpi drivers or video.ko driver.
> Index: linux-pm/include/linux/acpi.h
> ===================================================================
> --- linux-pm.orig/include/linux/acpi.h
> +++ linux-pm/include/linux/acpi.h
> @@ -191,7 +191,6 @@ extern bool wmi_has_guid(const char *gui
>  #define ACPI_VIDEO_BACKLIGHT_DMI_VIDEO			0x0200
>  #define ACPI_VIDEO_OUTPUT_SWITCHING_DMI_VENDOR		0x0400
>  #define ACPI_VIDEO_OUTPUT_SWITCHING_DMI_VIDEO		0x0800
> -#define ACPI_VIDEO_SKIP_BACKLIGHT			0x1000
>  
>  #if defined(CONFIG_ACPI_VIDEO) || defined(CONFIG_ACPI_VIDEO_MODULE)
>  
> Index: linux-pm/drivers/acpi/internal.h
> ===================================================================
> --- linux-pm.orig/drivers/acpi/internal.h
> +++ linux-pm/drivers/acpi/internal.h
> @@ -169,10 +169,8 @@ int acpi_create_platform_device(struct a
>    -------------------------------------------------------------------------- */
>  #if defined(CONFIG_ACPI_VIDEO) || defined(CONFIG_ACPI_VIDEO_MODULE)
>  bool acpi_video_backlight_quirks(void);
> -bool acpi_video_verify_backlight_support(void);
>  #else
>  static inline bool acpi_video_backlight_quirks(void) { return false; }
> -static inline bool acpi_video_verify_backlight_support(void) { return false; }
>  #endif
>  
>  #endif /* _ACPI_INTERNAL_H_ */
> 


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