llama: enable the EC backlight override for mediatek platform.

1. Override the panel backlight enable signal from SoC in llama board,
   force the backlight off on lid close.
2. Revise the function llama_lid_event to mtk_lid_event, makes more sense.

BRANCH=master
BUG=none
TEST=lid switch to open/close, observe the LCD backlight behavior.
     the backlight should be off, when lid is close.
     the backlight should be on, when lid is open.
BOARD=llama

Change-Id: Id1bff440c8bb6cee19c82615e916b8a2f2aa62ac
Signed-off-by: Ben Lok <ben.lok@mediatek.com>
(cherry picked from commit a90516b0a5493a55536e29d550f65cc743156710)
Reviewed-on: https://chromium-review.googlesource.com/255441
Reviewed-by: Rong Chang <rongchang@chromium.org>

2 files changed, 35 insertions, 2 deletions

diff --git a/board/llama/gpio.inc b/board/llama/gpio.inc
index 795c870143..0ad76346c7 100644
--- a/board/llama/gpio.inc
+++ b/board/llama/gpio.inc
@@ -32,6 +32,7 @@ GPIO(KB_IN07, D, 2,  GPIO_KB_INPUT, keyboard_raw_gpio_interrupt)
 /* Outputs */
 GPIO(BAT_LED0,          B, 11, GPIO_OUT_LOW,   NULL)   /* LED_GREEN */
 GPIO(BAT_LED1,          A, 11, GPIO_OUT_LOW,   NULL)   /* LED_ORANGE */
+GPIO(EC_BL_OVERRIDE,    F, 1,  GPIO_OUT_LOW,   NULL)
 GPIO(EC_INT,            B, 9,  GPIO_OUT_HIGH,  NULL)
 GPIO(ENTERING_RW,       F, 0,  GPIO_OUT_LOW,   NULL)
 GPIO(KB_OUT00,          B, 0,  GPIO_KB_OUTPUT, NULL)
diff --git a/power/mediatek.c b/power/mediatek.c
index 8515c27310..e4b54c59d9 100644
--- a/power/mediatek.c
+++ b/power/mediatek.c
@@ -140,6 +140,16 @@ enum power_on_event_t {
 	POWER_ON_EVENT_COUNT,
 };
 
+/**
+ * Parameters of mtk_backlight_override().
+ */
+enum blacklight_override_t {
+	MTK_BACKLIGHT_FORCE_OFF,
+	MTK_BACKLIGHT_CONTROL_BY_SOC,
+
+	MTK_BACKLIGHT_OVERRIDE_COUNT,
+};
+
 /* Forward declaration */
 static void chipset_turn_off_power_rails(void);
 
@@ -261,8 +271,30 @@ static int check_for_power_off_event(void)
 	return POWER_OFF_CANCEL;
 }
 
-static void llama_lid_event(void)
+/**
+ * Set the LCD backlight enable pin and override the signal from SoC.
+ *
+ * @param asserted	MTK_BACKLIGHT_FORCE_OFF, force off the panel backlight
+ *			MTK_BACKLIGHT_CONTROL_BY_SOC, leave the control to SOC
+ */
+static void mtk_backlight_override(enum blacklight_override_t asserted)
+{
+	/* Signal is active-low */
+	gpio_set_level(GPIO_EC_BL_OVERRIDE, !asserted);
+}
+
+static void mtk_lid_event(void)
 {
+	enum blacklight_override_t bl_override;
+
+	/* Override the panel backlight enable signal from SoC,
+	 * force the backlight off on lid close.
+	 */
+	bl_override = lid_is_open() ?
+		MTK_BACKLIGHT_CONTROL_BY_SOC :
+		MTK_BACKLIGHT_FORCE_OFF;
+	mtk_backlight_override(bl_override);
+
 	/* Power task only cares about lid-open events */
 	if (!lid_is_open())
 		return;
@@ -270,7 +302,7 @@ static void llama_lid_event(void)
 	lid_opened = 1;
 	task_wake(TASK_ID_CHIPSET);
 }
-DECLARE_HOOK(HOOK_LID_CHANGE, llama_lid_event, HOOK_PRIO_DEFAULT);
+DECLARE_HOOK(HOOK_LID_CHANGE, mtk_lid_event, HOOK_PRIO_DEFAULT);
 
 enum power_state power_chipset_init(void)
 {