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authorAaron Lu <aaron.lu@intel.com>2013-04-22 14:08:32 +0200
committerRafael J. Wysocki <rafael.j.wysocki@intel.com>2013-04-22 14:08:32 +0200
commita50188dae3089dcd15a6ae793528c157680891f1 (patch)
treeadb84d398f5c3e3b2e0b24c46672f5dfc91da862 /drivers/acpi
parent34f8f1031cdccc73ab002dfe5f65ec89c3314457 (diff)
downloadvexpress-lsk-a50188dae3089dcd15a6ae793528c157680891f1.tar.gz
acpi: video: enhance the quirk detect logic of _BQC
Currently we decide if the _BQC is using index by first setting the level to maximum, and then check if _BQC returned maximum; if not, we say it is using index. This is not true for some buggy systems, where the _BQC method will always return a constant value(e.g. 0 or 100 for the two broken system) and thus break the current logic. So this patch tries to enhance the quirk detect logic for _BQC: we do this by picking a test_level, it can be the maximum level or the mininum one based on some condition. And we don't make the assumption that if _BQC returned a value that is not what we just set, it must be using an index. Instead, we will compare the value returned from _BQC and if it doesn't match, see if the returned value is an index. And if still no, clear the capability of _BQC. References: https://bugzilla.kernel.org/show_bug.cgi?id=42861 References: https://bugzilla.kernel.org/show_bug.cgi?id=56011 Reported-and-tested-by: Artem Savkov <artem.savkov@gmail.com> Reported-by: Luis Medinas <lmedinas@gmail.com> Reported-by: Cheppes <cheppes@mailinator.com> Signed-off-by: Aaron Lu <aaron.lu@intel.com> Acked-by: Zhang Rui <rui.zhang@intel.com> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Diffstat (limited to 'drivers/acpi')
-rw-r--r--drivers/acpi/video.c67
1 files changed, 57 insertions, 10 deletions
diff --git a/drivers/acpi/video.c b/drivers/acpi/video.c
index 3cdd0471bc6..ed192e5d82b 100644
--- a/drivers/acpi/video.c
+++ b/drivers/acpi/video.c
@@ -632,6 +632,56 @@ acpi_video_cmp_level(const void *a, const void *b)
}
/*
+ * Decides if _BQC/_BCQ for this system is usable
+ *
+ * We do this by changing the level first and then read out the current
+ * brightness level, if the value does not match, find out if it is using
+ * index. If not, clear the _BQC/_BCQ capability.
+ */
+static int acpi_video_bqc_quirk(struct acpi_video_device *device,
+ int max_level, int current_level)
+{
+ struct acpi_video_device_brightness *br = device->brightness;
+ int result;
+ unsigned long long level;
+ int test_level;
+
+ /* don't mess with existing known broken systems */
+ if (bqc_offset_aml_bug_workaround)
+ return 0;
+
+ /*
+ * Some systems always report current brightness level as maximum
+ * through _BQC, we need to test another value for them.
+ */
+ test_level = current_level == max_level ? br->levels[2] : max_level;
+
+ result = acpi_video_device_lcd_set_level(device, test_level);
+ if (result)
+ return result;
+
+ result = acpi_video_device_lcd_get_level_current(device, &level, true);
+ if (result)
+ return result;
+
+ if (level != test_level) {
+ /* buggy _BQC found, need to find out if it uses index */
+ if (level < br->count) {
+ if (br->flags._BCL_reversed)
+ level = br->count - 3 - level;
+ if (br->levels[level + 2] == test_level)
+ br->flags._BQC_use_index = 1;
+ }
+
+ if (!br->flags._BQC_use_index)
+ device->cap._BQC = device->cap._BCQ = 0;
+ }
+
+ return 0;
+}
+
+
+/*
* Arg:
* device : video output device (LCD, CRT, ..)
*
@@ -742,18 +792,15 @@ acpi_video_init_brightness(struct acpi_video_device *device)
if (result)
goto out_free_levels;
- /*
- * Set the level to maximum and check if _BQC uses indexed value
- */
- result = acpi_video_device_lcd_set_level(device, max_level);
- if (result)
- goto out_free_levels;
-
- result = acpi_video_device_lcd_get_level_current(device, &level, true);
+ result = acpi_video_bqc_quirk(device, max_level, level_old);
if (result)
goto out_free_levels;
-
- br->flags._BQC_use_index = (level == max_level ? 0 : 1);
+ /*
+ * cap._BQC may get cleared due to _BQC is found to be broken
+ * in acpi_video_bqc_quirk, so check again here.
+ */
+ if (!device->cap._BQC)
+ goto set_level;
if (use_bios_initial_backlight) {
level = acpi_video_bqc_value_to_level(device, level_old);