Commit e11aecf1 authored by Henrique de Moraes Holschuh's avatar Henrique de Moraes Holschuh Committed by Len Brown
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ACPI: thinkpad-acpi: fix brightness dimming control bug 



ibm-acpi and thinkpad-acpi did not know about bit 5 of the EC backlight
level control register (EC 0x31), so it was always forced to zero on
any writes.

This would disable the BIOS option to *not* use a dimmer backlight level
scale while on battery, and who knows what else (there are two other
control bits of unknown function).

Bit 5 controls the "reduce backlight levels when on battery" optional
functionality (active low).  Bits 6 and 7 are better left alone as well,
instead of being forced to zero.

Signed-off-by: default avatarHenrique de Moraes Holschuh <hmh@hmh.eng.br>
Signed-off-by: default avatarLen Brown <len.brown@intel.com>
parent 2d5e94d7

drivers/misc/thinkpad_acpi.c

+49 −15
Original line number Diff line number Diff line
@@ -4295,8 +4295,16 @@ static struct ibm_struct ecdump_driver_data = { 


#define TPACPI_BACKLIGHT_DEV_NAME "thinkpad_screen"



enum {

	TP_EC_BACKLIGHT = 0x31,



	/* TP_EC_BACKLIGHT bitmasks */

	TP_EC_BACKLIGHT_LVLMSK = 0x1F,

	TP_EC_BACKLIGHT_CMDMSK = 0xE0,

	TP_EC_BACKLIGHT_MAPSW = 0x20,

};



static struct backlight_device *ibm_backlight_device;

static int brightness_offset = 0x31;

static int brightness_mode;

static unsigned int brightness_enable = 2; /* 2 = auto, 0 = no, 1 = yes */
@@ -4305,16 +4313,24 @@ static struct mutex brightness_mutex; 
/*

 * ThinkPads can read brightness from two places: EC 0x31, or

 * CMOS NVRAM byte 0x5E, bits 0-3.

 *

 * EC 0x31 has the following layout

 *   Bit 7: unknown function

 *   Bit 6: unknown function

 *   Bit 5: Z: honour scale changes, NZ: ignore scale changes

 *   Bit 4: must be set to zero to avoid problems

 *   Bit 3-0: backlight brightness level

 *

 * brightness_get_raw returns status data in the EC 0x31 layout

 */

static int brightness_get(struct backlight_device *bd)

static int brightness_get_raw(int *status)

{

	u8 lec = 0, lcmos = 0, level = 0;



	if (brightness_mode & 1) {

		if (!acpi_ec_read(brightness_offset, &lec))

		if (!acpi_ec_read(TP_EC_BACKLIGHT, &lec))

			return -EIO;

		lec &= (tp_features.bright_16levels)? 0x0f : 0x07;

		level = lec;

		level = lec & TP_EC_BACKLIGHT_LVLMSK;

	};

	if (brightness_mode & 2) {

		lcmos = (nvram_read_byte(TP_NVRAM_ADDR_BRIGHTNESS)
@@ -4325,6 +4341,8 @@ static int brightness_get(struct backlight_device *bd) 
	}



	if (brightness_mode == 3) {

		*status = lec;	/* Prefer EC, CMOS is just a backing store */

		lec &= TP_EC_BACKLIGHT_LVLMSK;

		if (lec == lcmos)

			tp_warned.bright_cmos_ec_unsync = 0;

		else {
@@ -4338,9 +4356,11 @@ static int brightness_get(struct backlight_device *bd) 
			}

			return -EIO;

		}

	} else {

		*status = level;

	}



	return level;

	return 0;

}



/* May return EINTR which can always be mapped to ERESTARTSYS */
@@ -4348,19 +4368,22 @@ static int brightness_set(int value) 
{

	int cmos_cmd, inc, i, res;

	int current_value;

	int command_bits;



	if (value > ((tp_features.bright_16levels)? 15 : 7))

	if (value > ((tp_features.bright_16levels)? 15 : 7) ||

	    value < 0)

		return -EINVAL;



	res = mutex_lock_interruptible(&brightness_mutex);

	if (res < 0)

		return res;



	current_value = brightness_get(NULL);

	if (current_value < 0) {

		res = current_value;

	res = brightness_get_raw(&current_value);

	if (res < 0)

		goto errout;

	}



	command_bits = current_value & TP_EC_BACKLIGHT_CMDMSK;

	current_value &= TP_EC_BACKLIGHT_LVLMSK;



	cmos_cmd = value > current_value ?

			TP_CMOS_BRIGHTNESS_UP :
@@ -4375,7 +4398,8 @@ static int brightness_set(int value) 
			goto errout;

		}

		if ((brightness_mode & 1) &&

		    !acpi_ec_write(brightness_offset, i + inc)) {

		    !acpi_ec_write(TP_EC_BACKLIGHT,

				   (i + inc) | command_bits)) {

			res = -EIO;

			goto errout;;

		}
@@ -4398,6 +4422,17 @@ static int brightness_update_status(struct backlight_device *bd) 
				bd->props.brightness : 0);

}



static int brightness_get(struct backlight_device *bd)

{

	int status, res;



	res = brightness_get_raw(&status);

	if (res < 0)

		return 0; /* FIXME: teach backlight about error handling */



	return status & TP_EC_BACKLIGHT_LVLMSK;

}



static struct backlight_ops ibm_backlight_data = {

	.get_brightness = brightness_get,

	.update_status  = brightness_update_status,
@@ -4462,8 +4497,7 @@ static int __init brightness_init(struct ibm_init_struct *iibm) 
	if (brightness_mode > 3)

		return -EINVAL;



	b = brightness_get(NULL);

	if (b < 0)

	if (brightness_get_raw(&b) < 0)

		return 1;



	if (tp_features.bright_16levels)
@@ -4481,7 +4515,7 @@ static int __init brightness_init(struct ibm_init_struct *iibm) 


	ibm_backlight_device->props.max_brightness =

				(tp_features.bright_16levels)? 15 : 7;

	ibm_backlight_device->props.brightness = b;

	ibm_backlight_device->props.brightness = b & TP_EC_BACKLIGHT_LVLMSK;

	backlight_update_status(ibm_backlight_device);



	return 0;

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