platform/x86: dell-laptop: Add keyboard backlight timeout AC settings

When changing keyboard backlight state on new Dell laptops, firmware
expects a new timeout AC value filled in Set New State SMBIOS call.

Without it any change of keyboard backlight state on new Dell laptops
fails. And user can see following error message in dmesg:

  dell_laptop: Setting old previous keyboard state failed
  leds dell::kbd_backlight: Setting an LED's brightness failed (-6)

This patch adds support for retrieving current timeout AC values and also
updating them. Current timeout value in sysfs is displayed based on current
AC status, like current display brightness value.

Detection if Dell laptop supports or not new timeout AC settings is done by
checking existence of Keyboard Backlight with AC SMBIOS token (0x0451).
Signed-off-by: Pali Rohár <pali.rohar@gmail.com>
Acked-by: Mario Limonciello <mario.limonciello@dell.com>
Tested-by: Arcadiy Ivanov <arcadiy@ivanov.biz>
[andy: fixed merge conflict with defined constants]
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>

drivers/platform/x86/dell-laptop.c

@@ -45,6 +45,7 @@
 #define KBD_LED_AUTO_100_TOKEN 0x02F6
 #define GLOBAL_MIC_MUTE_ENABLE 0x0364
 #define GLOBAL_MIC_MUTE_DISABLE 0x0365
+#define KBD_LED_AC_TOKEN 0x0451
 
 struct quirk_entry {
 	u8 touchpad_led;
@@ -1027,7 +1028,7 @@ static void touchpad_led_exit(void)
  *     bit 2     Pointing stick
  *     bit 3     Any mouse
  *     bits 4-7  Reserved for future use
- *  cbRES2, byte3  Current Timeout
+ *  cbRES2, byte3  Current Timeout on battery
  *     bits 7:6  Timeout units indicator:
  *     00b       Seconds
  *     01b       Minutes
@@ -1039,6 +1040,15 @@ static void touchpad_led_exit(void)
  *  cbRES3, byte0  Current setting of ALS value that turns the light on or off.
  *  cbRES3, byte1  Current ALS reading
  *  cbRES3, byte2  Current keyboard light level.
+ *  cbRES3, byte3  Current timeout on AC Power
+ *     bits 7:6  Timeout units indicator:
+ *     00b       Seconds
+ *     01b       Minutes
+ *     10b       Hours
+ *     11b       Days
+ *     Bits 5:0  Timeout value (0-63) in sec/min/hr/day
+ *     NOTE: A value of 0 means always on (no timeout) if any bits of RES3 byte2
+ *     are set upon return from the upon return from the [Get Feature information] call.
  *
  * cbArg1 0x2 = Set New State
  *  cbRES1         Standard return codes (0, -1, -2)
@@ -1061,7 +1071,7 @@ static void touchpad_led_exit(void)
  *     bit 2     Pointing stick
  *     bit 3     Any mouse
  *     bits 4-7  Reserved for future use
- *  cbArg2, byte3  Desired Timeout
+ *  cbArg2, byte3  Desired Timeout on battery
  *     bits 7:6  Timeout units indicator:
  *     00b       Seconds
  *     01b       Minutes
@@ -1070,6 +1080,13 @@ static void touchpad_led_exit(void)
  *     bits 5:0  Timeout value (0-63) in sec/min/hr/day
  *  cbArg3, byte0  Desired setting of ALS value that turns the light on or off.
  *  cbArg3, byte2  Desired keyboard light level.
+ *  cbArg3, byte3  Desired Timeout on AC power
+ *     bits 7:6  Timeout units indicator:
+ *     00b       Seconds
+ *     01b       Minutes
+ *     10b       Hours
+ *     11b       Days
+ *     bits 5:0  Timeout value (0-63) in sec/min/hr/day
  */
 
 
@@ -1115,6 +1132,8 @@ struct kbd_state {
 	u8 triggers;
 	u8 timeout_value;
 	u8 timeout_unit;
+	u8 timeout_value_ac;
+	u8 timeout_unit_ac;
 	u8 als_setting;
 	u8 als_value;
 	u8 level;
@@ -1134,6 +1153,7 @@ static u16 kbd_token_bits;
 static struct kbd_info kbd_info;
 static bool kbd_als_supported;
 static bool kbd_triggers_supported;
+static bool kbd_timeout_ac_supported;
 
 static u8 kbd_mode_levels[16];
 static int kbd_mode_levels_count;
@@ -1273,6 +1293,8 @@ static int kbd_get_state(struct kbd_state *state)
 	state->als_setting = buffer->output[2] & 0xFF;
 	state->als_value = (buffer->output[2] >> 8) & 0xFF;
 	state->level = (buffer->output[2] >> 16) & 0xFF;
+	state->timeout_value_ac = (buffer->output[2] >> 24) & 0x3F;
+	state->timeout_unit_ac = (buffer->output[2] >> 30) & 0x3;
 
  out:
 	dell_smbios_release_buffer();
@@ -1292,6 +1314,8 @@ static int kbd_set_state(struct kbd_state *state)
 	buffer->input[1] |= (state->timeout_unit & 0x3) << 30;
 	buffer->input[2] = state->als_setting & 0xFF;
 	buffer->input[2] |= (state->level & 0xFF) << 16;
+	buffer->input[2] |= (state->timeout_value_ac & 0x3F) << 24;
+	buffer->input[2] |= (state->timeout_unit_ac & 0x3) << 30;
 	dell_smbios_send_request(4, 11);
 	ret = buffer->output[0];
 	dell_smbios_release_buffer();
@@ -1398,6 +1422,13 @@ static inline int kbd_init_info(void)
 	if (ret)
 		return ret;
 
+	/* NOTE: Old models without KBD_LED_AC_TOKEN token supports only one
+	 *       timeout value which is shared for both battery and AC power
+	 *       settings. So do not try to set AC values on old models.
+	 */
+	if (dell_smbios_find_token(KBD_LED_AC_TOKEN))
+		kbd_timeout_ac_supported = true;
+
 	kbd_get_state(&state);
 
 	/* NOTE: timeout value is stored in 6 bits so max value is 63 */
@@ -1579,8 +1610,14 @@ static ssize_t kbd_led_timeout_store(struct device *dev,
 		goto out;
 
 	new_state = state;
-	new_state.timeout_value = value;
-	new_state.timeout_unit = unit;
+
+	if (kbd_timeout_ac_supported && power_supply_is_system_supplied() > 0) {
+		new_state.timeout_value_ac = value;
+		new_state.timeout_unit_ac = unit;
+	} else {
+		new_state.timeout_value = value;
+		new_state.timeout_unit = unit;
+	}
 
 	ret = kbd_set_state_safe(&new_state, &state);
 	if (ret)
@@ -1596,16 +1633,26 @@ static ssize_t kbd_led_timeout_show(struct device *dev,
 				    struct device_attribute *attr, char *buf)
 {
 	struct kbd_state state;
+	int value;
 	int ret;
 	int len;
+	u8 unit;
 
 	ret = kbd_get_state(&state);
 	if (ret)
 		return ret;
 
-	len = sprintf(buf, "%d", state.timeout_value);
+	if (kbd_timeout_ac_supported && power_supply_is_system_supplied() > 0) {
+		value = state.timeout_value_ac;
+		unit = state.timeout_unit_ac;
+	} else {
+		value = state.timeout_value;
+		unit = state.timeout_unit;
+	}
+
+	len = sprintf(buf, "%d", value);
 
-	switch (state.timeout_unit) {
+	switch (unit) {
 	case KBD_TIMEOUT_SECONDS:
 		return len + sprintf(buf+len, "s\n");
 	case KBD_TIMEOUT_MINUTES: