ACPI / video / i915: No ACPI backlight if firmware expects Windows 8

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 includes a fix from Aaron Lu's.

References: https://bugzilla.kernel.org/show_bug.cgi?id=51231
Tested-by: Aaron Lu <aaron.lu@intel.com>
Tested-by: Igor Gnatenko <i.gnatenko.brain@gmail.com>
Tested-by: Yves-Alexis Perez <corsac@debian.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: Aaron Lu <aaron.lu@intel.com>
Acked-by: Matthew Garrett <matthew.garrett@nebula.com>

diff --git a/drivers/acpi/internal.h b/drivers/acpi/internal.h
index 3a50a34fe176b34bb77a3ff8cfff9588fe523da8..227aca77ee1ef7777277d34a4b5e5774efa1286e 100644 (file)
--- a/drivers/acpi/internal.h
+++ b/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
+  -------------------------------------------------------------------------- */
+#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_ */

diff --git a/drivers/acpi/video.c b/drivers/acpi/video.c
index f236e172d948979bc40230b97a0512a1c8085d08..e9d4bb60c35c1c98f22bdbf3617a75b09d9767e8 100644 (file)
--- a/drivers/acpi/video.c
+++ b/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"
@@ -901,7 +903,7 @@ static void acpi_video_device_find_cap(struct acpi_video_device *device)
        if (acpi_video_init_brightness(device))
                return;
 
-       if (acpi_video_backlight_support()) {
+       if (acpi_video_verify_backlight_support()) {
                struct backlight_properties props;
                struct pci_dev *pdev;
                acpi_handle acpi_parent;
@@ -1356,8 +1358,8 @@ acpi_video_switch_brightness(struct acpi_video_device *device, int event)
        unsigned long long level_current, level_next;
        int result = -EINVAL;
 
-       /* no warning message if acpi_backlight=vendor is used */
-       if (!acpi_video_backlight_support())
+       /* no warning message if acpi_backlight=vendor or a quirk is used */
+       if (!acpi_video_verify_backlight_support())
                return 0;
 
        if (!device->brightness)
@@ -1859,6 +1861,46 @@ static int acpi_video_bus_remove(struct acpi_device *device)
        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)
@@ -1890,14 +1932,25 @@ static int __init intel_opregion_present(void)
        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;
        }
 
@@ -1913,7 +1966,7 @@ int acpi_video_register(void)
 
        return 0;
 }
-EXPORT_SYMBOL(acpi_video_register);
+EXPORT_SYMBOL(__acpi_video_register);
 
 void acpi_video_unregister(void)
 {

diff --git a/drivers/acpi/video_detect.c b/drivers/acpi/video_detect.c
index e6bd910bc6edee4b55e3b6de7888bdd5c5ec06f6..826e52def08074bad91038ad25df387917b690ec 100644 (file)
--- a/drivers/acpi/video_detect.c
+++ b/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 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.

diff --git a/drivers/gpu/drm/i915/i915_dma.c b/drivers/gpu/drm/i915/i915_dma.c
index adb319b53ecd4acb98e1ce35f599ea935ff83dce..cf188ab7051a6b213e0ebb945fde92fc869b0ce6 100644 (file)
--- a/drivers/gpu/drm/i915/i915_dma.c
+++ b/drivers/gpu/drm/i915/i915_dma.c
@@ -1648,7 +1648,7 @@ int i915_driver_load(struct drm_device *dev, unsigned long flags)
        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))

diff --git a/include/acpi/video.h b/include/acpi/video.h
index 61109f2609fc3ee446ec43e242875b28ae719344..b26dc4fb7ba8283f22b0d8f646a58a06fd00d510 100644 (file)
--- a/include/acpi/video.h
+++ b/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)

diff --git a/include/linux/acpi.h b/include/linux/acpi.h
index 353ba256f3681e4f6ddd8b18b9feba61b1d98cec..6ad72f92469c556368742f7c2d3301acfcfd5a0c 100644 (file)
--- a/include/linux/acpi.h
+++ b/include/linux/acpi.h
@@ -191,6 +191,7 @@ extern bool wmi_has_guid(const char *guid);
 #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)