Re: [Update][PATCH] ACPI / video / i915: Remove ACPI backlight if firmware expects Windows 8

[Aaron Lu <aaron.lwe@gmail.com>]

On 07/15/2013 07:42 PM, Rafael J. Wysocki wrote:
> On Monday, July 15, 2013 10:36:15 AM Aaron Lu wrote:
>> On 07/13/2013 08:46 AM, Rafael J. Wysocki wrote:
>>> From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
>>>
>>> According to Matthew Garrett, "Windows 8 leaves backlight control up
>>> to individual graphics drivers rather than making ACPI calls itself.
>>> There's plenty of evidence to suggest that the Intel driver for
>>> Windows [8] doesn't use the ACPI interface, including the fact that
>>> it's broken on a bunch of machines when the OS claims to support
>>> Windows 8.  The simplest thing to do appears to be to disable the
>>> ACPI backlight interface on these systems".
>>>
>>> There's a problem with that approach, however, because simply
>>> avoiding to register the ACPI backlight interface if the firmware
>>> calls _OSI for Windows 8 may not work in the following situations:
>>>  (1) The ACPI backlight interface actually works on the given system
>>>      and the i915 driver is not loaded (e.g. another graphics driver
>>>      is used).
>>>  (2) The ACPI backlight interface doesn't work on the given system,
>>>      but there is a vendor platform driver that will register its
>>>      own, equally broken, backlight interface if not prevented from
>>>      doing so by the ACPI subsystem.
>>> Therefore we need to allow the ACPI backlight interface to be
>>> registered until the i915 driver is loaded which then will unregister
>>> it if the firmware has called _OSI for Windows 8 (or will register
>>> the ACPI video driver without backlight support if not already
>>> present).
>>>
>>> For this reason, introduce an alternative function for registering
>>> ACPI video, acpi_video_register_with_quirks(), that will check
>>> whether or not the ACPI video driver has already been registered
>>> and whether or not the backlight Windows 8 quirk has to be applied.
>>> If the quirk has to be applied, it will block the ACPI backlight
>>> support and either unregister the backlight interface if the ACPI
>>> video driver has already been registered, or register the ACPI
>>> video driver without the backlight interface otherwise.  Make
>>> the i915 driver use acpi_video_register_with_quirks() instead of
>>> acpi_video_register() in i915_driver_load().
>>>
>>> This change is based on earlier patches from Matthew Garrett,
>>> Chun-Yi Lee and Seth Forshee and Aaron Lu's comments.
>>>
>>> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
>>
>> Reviewed-by: Aaron Lu <aaron.lu@intel.com>
>>
>> BTW, I also tested on a Toshiba laptop Z830 where its AML code
>> claims support of win8, the result is as expected: ACPI video
>> interface is removed, i915 Xorg driver picks intel_backlight.
>>
>> Thanks for the fix.
> 
> Cool, thanks for testing this!
> 
> Can you please also ask bug reporters in the BZ entires related to this to test
> it too?

Sure.

To be clear, I actually tested the patch in your linux-next branch,
which turned out to be a little different in that you have fixed the
problem Igor raised here.

I'll ask reporters to test on a stable tree with the following two
patches on top:
https://patchwork.kernel.org/patch/2812951/ (expose OSI version)
https://patchwork.kernel.org/patch/2827793/ (your updated patch)
or your linux-next branch, whichever they like.

-Aaron

> 
> Rafael
> 
> 
>>> ---
>>>  drivers/acpi/internal.h         |   11 ++++++
>>>  drivers/acpi/video.c            |   65 ++++++++++++++++++++++++++++++++++++----
>>>  drivers/acpi/video_detect.c     |   21 ++++++++++++
>>>  drivers/gpu/drm/i915/i915_dma.c |    2 -
>>>  include/acpi/video.h            |   11 ++++++
>>>  include/linux/acpi.h            |    1 
>>>  6 files changed, 103 insertions(+), 8 deletions(-)
>>>
>>> Index: linux-pm/drivers/acpi/video.c
>>> ===================================================================
>>> --- linux-pm.orig/drivers/acpi/video.c
>>> +++ linux-pm/drivers/acpi/video.c
>>> @@ -44,6 +44,8 @@
>>>  #include <linux/suspend.h>
>>>  #include <acpi/video.h>
>>>  
>>> +#include "internal.h"
>>> +
>>>  #define PREFIX "ACPI: "
>>>  
>>>  #define ACPI_VIDEO_BUS_NAME		"Video Bus"
>>> @@ -898,7 +900,7 @@ static void acpi_video_device_find_cap(s
>>>  		device->cap._DDC = 1;
>>>  	}
>>>  
>>> -	if (acpi_video_backlight_support()) {
>>> +	if (acpi_video_verify_backlight_support()) {
>>>  		struct backlight_properties props;
>>>  		struct pci_dev *pdev;
>>>  		acpi_handle acpi_parent;
>>> @@ -1854,6 +1856,46 @@ 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)
>>> @@ -1885,14 +1927,25 @@ static int __init intel_opregion_present
>>>  	return opregion;
>>>  }
>>>  
>>> -int acpi_video_register(void)
>>> +int __acpi_video_register(bool backlight_quirks)
>>>  {
>>> -	int result = 0;
>>> +	bool no_backlight;
>>> +	int result;
>>> +
>>> +	no_backlight = backlight_quirks ? acpi_video_backlight_quirks() : false;
>>> +
>>>  	if (register_count) {
>>>  		/*
>>> -		 * if the function of acpi_video_register is already called,
>>> -		 * don't register the acpi_vide_bus again and return no error.
>>> +		 * 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 (no_backlight)
>>> +			acpi_walk_namespace(ACPI_TYPE_DEVICE, ACPI_ROOT_OBJECT,
>>> +					    ACPI_UINT32_MAX,
>>> +					    video_unregister_backlight,
>>> +					    NULL, NULL, NULL);
>>> +
>>>  		return 0;
>>>  	}
>>>  
>>> @@ -1908,7 +1961,7 @@ int acpi_video_register(void)
>>>  
>>>  	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
>>> @@ -1660,7 +1660,7 @@ 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();
>>> +		acpi_video_register_with_quirks();
>>>  	}
>>>  
>>>  	if (IS_GEN5(dev))
>>> Index: linux-pm/include/acpi/video.h
>>> ===================================================================
>>> --- linux-pm.orig/include/acpi/video.h
>>> +++ linux-pm/include/acpi/video.h
>>> @@ -17,12 +17,21 @@ 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(void);
>>> +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 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
>>> @@ -38,6 +38,8 @@
>>>  #include <linux/dmi.h>
>>>  #include <linux/pci.h>
>>>  
>>> +#include "internal.h"
>>> +
>>>  #define PREFIX "ACPI: "
>>>  
>>>  ACPI_MODULE_NAME("video");
>>> @@ -234,6 +236,17 @@ static void acpi_video_caps_check(void)
>>>  		acpi_video_get_capabilities(NULL);
>>>  }
>>>  
>>> +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;
>>> +}
>>> +EXPORT_SYMBOL(acpi_video_backlight_quirks);
>>> +
>>>  /* Promote the vendor interface instead of the generic video module.
>>>   * This function allow DMI blacklists to be implemented by externals
>>>   * platform drivers instead of putting a big blacklist in video_detect.c
>>> @@ -278,6 +291,14 @@ int acpi_video_backlight_support(void)
>>>  }
>>>  EXPORT_SYMBOL(acpi_video_backlight_support);
>>>  
>>> +/* For the ACPI video driver's 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
>>> @@ -191,6 +191,7 @@ 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
>>> @@ -164,4 +164,15 @@ struct platform_device;
>>>  int acpi_create_platform_device(struct acpi_device *adev,
>>>  				const struct acpi_device_id *id);
>>>  
>>> +/*--------------------------------------------------------------------------
>>> +					Video
>>> +  -------------------------------------------------------------------------- */
>>> +#ifdef CONFIG_ACPI_VIDEO
>>> +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_ */
>>>
>>