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

Original-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>
(cherry picked from commit 1f091487b210125e351c8397186e2012d8a19cb7)

Change-Id: I1f9ca7179bd7bbc20a456a62c0c052b90e671055
Reviewed-on: https://gerrit.chromium.org/gerrit/30971
Reviewed-by: David Hendricks <dhendrix@chromium.org>
Reviewed-by: Che-Liang Chiou <clchiou@chromium.org>
Tested-by: Che-Liang Chiou <clchiou@chromium.org>

2 files changed, 32 insertions, 5 deletions

diff --git a/board/snow/board.c b/board/snow/board.c
index 8fe26dd15d..8bdca0cde9 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,