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Commit a50188da authored by Aaron Lu's avatar Aaron Lu Committed by Rafael J. Wysocki
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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: default avatarArtem Savkov <artem.savkov@gmail.com>
Reported-by: default avatarLuis Medinas <lmedinas@gmail.com>
Reported-by: default avatarCheppes <cheppes@mailinator.com>
Signed-off-by: default avatarAaron Lu <aaron.lu@intel.com>
Acked-by: default avatarZhang Rui <rui.zhang@intel.com>
Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
parent 34f8f103

drivers/acpi/video.c

+57 −10
Original line number Diff line number Diff line
@@ -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;



	/*

	 * Set the level to maximum and check if _BQC uses indexed value

	 */

	result = acpi_video_device_lcd_set_level(device, max_level);

	result = acpi_video_bqc_quirk(device, max_level, level_old);

	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);

	/*

	 * 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);