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: Henrique de Moraes Holschuh <hmh@xxxxxxxxxx>
---
drivers/misc/thinkpad_acpi.c | 64 ++++++++++++++++++++++++++++++++----------
1 files changed, 49 insertions(+), 15 deletions(-)
diff --git a/drivers/misc/thinkpad_acpi.c b/drivers/misc/thinkpad_acpi.c
index 3513d99..1a26423 100644
--- a/drivers/misc/thinkpad_acpi.c
+++ b/drivers/misc/thinkpad_acpi.c
@@ -4294,8 +4294,16 @@ 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 */
@@ -4304,16 +4312,24 @@ 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)
@@ -4324,6 +4340,8 @@ 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 {
@@ -4337,9 +4355,11 @@ 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 */
@@ -4347,19 +4367,22 @@ 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(¤t_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 :
@@ -4374,7 +4397,8 @@ 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;;
}
@@ -4397,6 +4421,17 @@ 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,
@@ -4461,8 +4496,7 @@ 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)
@@ -4480,7 +4514,7 @@ 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;
--
1.5.4.4
-------------------------------------------------------------------------
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