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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>
This commit is contained in:
Aaron Lu 2013-04-22 14:08:32 +02:00 committed by Rafael J. Wysocki
parent 34f8f1031c
commit a50188dae3
1 changed files with 57 additions and 10 deletions
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67
drivers/acpi/video.c
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@ -631,6 +631,56 @@ acpi_video_cmp_level(const void *a, const void *b)
return *(int *)a - *(int *)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;
result = acpi_video_bqc_quirk(device, max_level, level_old);
if (result)
goto out_free_levels;
/*
* Set the level to maximum and check if _BQC uses indexed value
* cap._BQC may get cleared due to _BQC is found to be broken
* in acpi_video_bqc_quirk, so check again here.
*/
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);
if (result)
goto out_free_levels;
br->flags._BQC_use_index = (level == max_level ? 0 : 1);
if (!device->cap._BQC)
goto set_level;
if (use_bios_initial_backlight) {
level = acpi_video_bqc_value_to_level(device, level_old);