snow/stm32: re-configure power LED on the fly (input vs. pwm)

Usually the power LED is driven by the PWM mode so that its nominal
brightness can be set to a "soft" on value. However, when
the LED is to remain off the LED should be switched to floating
input mode. This reduces voltage leakage.

This CL updates the power_led_task to configure the LED however is
appropriate and adds board functions to re-configure the GPIO.

Signed-off-by: David Hendricks <dhendrix@chromium.org>

BRANCH=snow
BUG=chrome-os-partner:12381
TEST=LED responds as expected in suspend and on/off states, also
tested that leakage is reduced with multimeter

Change-Id: If90ac78aaffe7358cce80dd02ec1423c2cb4f664
Reviewed-on: https://gerrit.chromium.org/gerrit/29705
Reviewed-by: Simon Glass <sjg@chromium.org>
Commit-Ready: David Hendricks <dhendrix@chromium.org>
Tested-by: David Hendricks <dhendrix@chromium.org>

4 files changed, 82 insertions, 12 deletions

diff --git a/board/snow/board.c b/board/snow/board.c
index 50fcdfd04c..b612955af3 100644
--- a/board/snow/board.c
+++ b/board/snow/board.c
@@ -12,6 +12,7 @@
 #include "gpio.h"
 #include "i2c.h"
 #include "pmu_tpschrome.h"
+#include "power_led.h"
 #include "registers.h"
 #include "spi.h"
 #include "timer.h"
@@ -67,6 +68,7 @@ const struct gpio_info gpio_list[GPIO_COUNT] = {
 	{"CHARGER_EN",  GPIO_B, (1<<2),  GPIO_OUT_LOW, NULL},
 	{"EC_INT",      GPIO_B, (1<<9),  GPIO_HI_Z, NULL},
 	{"CODEC_INT",   GPIO_D, (1<<1),  GPIO_HI_Z, NULL},
+	{"LED_POWER_L", GPIO_B, (1<<3),  GPIO_INPUT, NULL},
 	{"KB_OUT00",    GPIO_B, (1<<0),  GPIO_KB_OUTPUT, NULL},
 	{"KB_OUT01",    GPIO_B, (1<<8),  GPIO_KB_OUTPUT, NULL},
 	{"KB_OUT02",    GPIO_B, (1<<12), GPIO_KB_OUTPUT, NULL},
@@ -107,11 +109,6 @@ void configure_board(void)
 	STM32_GPIO_AFIO_MAPR = (STM32_GPIO_AFIO_MAPR & ~(0x3 << 8))
 			       | (1 << 8);
 
-	/* set power LED to alternate function to be driven by TIM2/PWM */
-	val = STM32_GPIO_CRL_OFF(GPIO_B) & ~0x0000f000;
-	val |= 0x00009000;
-	STM32_GPIO_CRL_OFF(GPIO_B) = val;
-
 	/*
 	 * I2C SCL/SDA on PB10-11 and PB6-7, bi-directional, no pull-up/down,
 	 * initialized as hi-Z until alt. function is set
@@ -152,6 +149,35 @@ void board_keyboard_suppress_noise(void)
 	gpio_set_level(GPIO_CODEC_INT, 1);
 }
 
+void board_power_led_config(enum powerled_config config)
+{
+	uint32_t val;
+
+	switch (config) {
+	case POWERLED_CONFIG_PWM:
+		val = STM32_GPIO_CRL_OFF(GPIO_B) & ~0x0000f000;
+		val |= 0x00009000;	/* alt. function (TIM2/PWM) */
+		STM32_GPIO_CRL_OFF(GPIO_B) = val;
+		break;
+	case POWERLED_CONFIG_MANUAL_OFF:
+		/*
+		 * Re-configure GPIO as a floating input. Alternatively we could
+		 * configure it as an open-drain output and set it to high
+		 * impedence, but reconfiguring as an input had better results
+		 * in testing.
+		 */
+		gpio_set_flags(GPIO_LED_POWER_L, GPIO_INPUT);
+		gpio_set_level(GPIO_LED_POWER_L, 1);
+		break;
+	case POWERLED_CONFIG_MANUAL_ON:
+		gpio_set_flags(GPIO_LED_POWER_L, GPIO_OUTPUT | GPIO_OPEN_DRAIN);
+		gpio_set_level(GPIO_LED_POWER_L, 0);
+		break;
+	default:
+		break;
+	}
+}
+
 enum {
 	/* Time between requesting bus and deciding that we have it */
 	BUS_SLEW_DELAY_US	= 10,
diff --git a/board/snow/board.h b/board/snow/board.h
index c7ecae04e7..07b29f0fb7 100644
--- a/board/snow/board.h
+++ b/board/snow/board.h
@@ -87,6 +87,7 @@ enum gpio_signal {
 	GPIO_CHARGER_EN,
 	GPIO_EC_INT,
 	GPIO_CODEC_INT,        /* To audio codec (KB noise cancellation) */
+	GPIO_LED_POWER_L,      /* Keyboard power LED */
 	GPIO_KB_OUT00,
 	GPIO_KB_OUT01,
 	GPIO_KB_OUT02,
diff --git a/chip/stm32/power_led.c b/chip/stm32/power_led.c
index a080dbfa07..bc354ee492 100644
--- a/chip/stm32/power_led.c
+++ b/chip/stm32/power_led.c
@@ -7,7 +7,8 @@
  * Keyboard power button LED state machine.
  *
  * This sets up TIM2 to drive the power button LED so that the duty cycle
- * can range from 0-100%.
+ * can range from 0-100%. When the lid is closed or turned off, then the
+ * PWM is disabled and the GPIO is reconfigured to minimize leakage voltage.
  *
  * In suspend mode, duty cycle transitions progressively slower from 0%
  * to 100%, and progressively faster from 100% back down to 0%. This
@@ -25,8 +26,9 @@
 #define LED_HOLD_TIME		330000	/* hold for 330ms at min/max */
 #define LED_STEP_PERCENT	4	/* incremental value of each step */
 
-static enum powerled_state led_state;
-static int power_led_percent;
+static enum powerled_state led_state = POWERLED_STATE_ON;
+static enum powerled_config led_config = POWERLED_CONFIG_MANUAL_OFF;
+static int power_led_percent = 100;
 
 void powerled_set_state(enum powerled_state new_state)
 {
@@ -35,8 +37,19 @@ void powerled_set_state(enum powerled_state new_state)
 	task_wake(TASK_ID_POWERLED);
 }
 
-static void power_led_timer_init(void)
+/* set board-level power LED config options (e.g. manual off/on, PWM) */
+void board_power_led_config(enum powerled_state config)
+		__attribute__((weak, alias("__board_power_led_config")));
+
+/* Provide a default function in case the board doesn't have one */
+void __board_power_led_config(enum powerled_config config)
+{
+}
+
+static void power_led_use_pwm(void)
 {
+	board_power_led_config(POWERLED_CONFIG_PWM);
+
 	/* enable TIM2 clock */
 	STM32_RCC_APB1ENR |= 0x1;
 
@@ -66,6 +79,20 @@ static void power_led_timer_init(void)
 
 	/* enable auto-reload preload, start counting */
 	STM32_TIM_CR1(2) |= (1 << 7) | (1 << 0);
+
+	led_config = POWERLED_CONFIG_PWM;
+}
+
+static void power_led_manual_off(void)
+{
+	/* disable counter */
+	STM32_TIM_CR1(2) &= ~0x1;
+
+	/* disable TIM2 clock */
+	STM32_RCC_APB1ENR &= ~0x1;
+
+	board_power_led_config(POWERLED_CONFIG_MANUAL_OFF);
+	led_config = POWERLED_CONFIG_MANUAL_OFF;
 }
 
 static void power_led_set_duty(int percent)
@@ -109,21 +136,31 @@ static int power_led_step(void)
 
 void power_led_task(void)
 {
-	power_led_timer_init();
-
 	while (1) {
 		int state_timeout = -1;
 
 		switch (led_state) {
 		case POWERLED_STATE_ON:
+			/*
+			 * "ON" implies driving the LED using the PWM with a
+			 * duty duty cycle of 100%. This produces a softer
+			 * brightness than setting the GPIO to solid ON.
+			 */
+			if (led_config != POWERLED_CONFIG_PWM)
+				power_led_use_pwm();
 			power_led_set_duty(100);
 			state_timeout = -1;
 			break;
 		case POWERLED_STATE_OFF:
-			power_led_set_duty(0);
+			/* reconfigure GPIO to disable the LED */
+			if (led_config != POWERLED_CONFIG_MANUAL_OFF)
+				power_led_manual_off();
 			state_timeout = -1;
 			break;
 		case POWERLED_STATE_SUSPEND:
+			/* drive using PWM with variable duty cycle */
+			if (led_config != POWERLED_CONFIG_PWM)
+				power_led_use_pwm();
 			state_timeout = power_led_step();
 			break;
 		default:
diff --git a/include/power_led.h b/include/power_led.h
index 9301a5fdf5..b255c557bb 100644
--- a/include/power_led.h
+++ b/include/power_led.h
@@ -25,6 +25,12 @@ enum powerled_state {
 	POWERLED_STATE_COUNT
 };
 
+enum powerled_config {
+	POWERLED_CONFIG_MANUAL_OFF,
+	POWERLED_CONFIG_MANUAL_ON,
+	POWERLED_CONFIG_PWM,
+};
+
 /* Set the power adapter LED to the specified color. */
 int powerled_set(enum powerled_color color);