Daisy/Snow: Drive power LED with PWM

This drives the power LED for Snow (PB3) using TIM2 in PWM mode.

Since timer setup and manipulation is STM32-specific, the power LED
logic moved to to chip/stm32/power_led.c.

This also adds a "powerled" console command for testing.

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

BUG=chrome-os-partner:10647
TEST=Tested on Snow with powerled command, compiled for Daisy

Change-Id: I5a7dc20d201ea058767e3e76d54e7c8567a3b83c
Reviewed-on: https://gerrit.chromium.org/gerrit/26267
Commit-Ready: David Hendricks <dhendrix@chromium.org>
Reviewed-by: David Hendricks <dhendrix@chromium.org>
Tested-by: David Hendricks <dhendrix@chromium.org>

6 files changed, 186 insertions, 60 deletions

diff --git a/board/snow/board.c b/board/snow/board.c
index b536ff3eda..4c9e30bd4b 100644
--- a/board/snow/board.c
+++ b/board/snow/board.c
@@ -56,7 +56,6 @@ const struct gpio_info gpio_list[GPIO_COUNT] = {
 	{"PMIC_PWRON_L",GPIO_A, (1<<12), GPIO_OUT_HIGH, NULL},
 	{"ENTERING_RW", GPIO_D, (1<<0),  GPIO_OUT_LOW, NULL},
 	{"CHARGER_EN",  GPIO_B, (1<<2),  GPIO_OUT_LOW, NULL},
-	{"POWER_LED_L", GPIO_B, (1<<3),  GPIO_OUT_HIGH, NULL},
 	{"EC_INT",      GPIO_B, (1<<9),  GPIO_HI_Z, NULL},
 	{"CODEC_INT",   GPIO_D, (1<<1),  GPIO_HI_Z, NULL},
 	{"KB_OUT00",    GPIO_B, (1<<0),  GPIO_KB_OUTPUT, NULL},
@@ -130,6 +129,15 @@ void configure_board(void)
 	STM32_GPIO_AFIO_MAPR = (STM32_GPIO_AFIO_MAPR & ~(0x7 << 24))
 			       | (2 << 24);
 
+	/* remap TIM2_CH2 to PB3 */
+	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
diff --git a/board/snow/board.h b/board/snow/board.h
index 15db5a64d7..c78a30f574 100644
--- a/board/snow/board.h
+++ b/board/snow/board.h
@@ -79,7 +79,6 @@ enum gpio_signal {
 	GPIO_PMIC_PWRON_L,     /* 5v rail ready */
 	GPIO_EC_ENTERING_RW,   /* EC is R/W mode for the kbc mux */
 	GPIO_CHARGER_EN,
-	GPIO_POWER_LED_L,      /* Power state keyboard LED */
 	GPIO_EC_INT,
 	GPIO_CODEC_INT,        /* To audio codec (KB noise cancellation) */
 	GPIO_KB_OUT00,
diff --git a/chip/stm32/build.mk b/chip/stm32/build.mk
index 013569cd75..33a7ffb943 100644
--- a/chip/stm32/build.mk
+++ b/chip/stm32/build.mk
@@ -9,7 +9,7 @@
 # STM32 SoC family has a Cortex-M3 ARM core
 CORE:=cortex-m
 
-chip-y=dma.o gpio.o hwtimer.o system.o uart.o
+chip-y=dma.o gpio.o hwtimer.o power_led.o system.o uart.o
 chip-y+=jtag-$(CHIP_VARIANT).o clock-$(CHIP_VARIANT).o gpio-$(CHIP_VARIANT).o
 chip-$(CONFIG_SPI)+=spi.o
 chip-$(CONFIG_I2C)+=i2c.o
diff --git a/chip/stm32/power_led.c b/chip/stm32/power_led.c
new file mode 100644
index 0000000000..a080dbfa07
--- /dev/null
+++ b/chip/stm32/power_led.c
@@ -0,0 +1,161 @@
+/* Copyright (c) 2012 The Chromium OS Authors. All rights reserved.
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+/*
+ * 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%.
+ *
+ * In suspend mode, duty cycle transitions progressively slower from 0%
+ * to 100%, and progressively faster from 100% back down to 0%. This
+ * results in a breathing effect. It takes about 2sec for a full cycle.
+ */
+
+#include "console.h"
+#include "power_led.h"
+#include "registers.h"
+#include "task.h"
+#include "timer.h"
+#include "util.h"
+
+#define LED_STATE_TIMEOUT_MIN	15000	/* minimum of 15ms per step */
+#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;
+
+void powerled_set_state(enum powerled_state new_state)
+{
+	led_state = new_state;
+	/* Wake up the task */
+	task_wake(TASK_ID_POWERLED);
+}
+
+static void power_led_timer_init(void)
+{
+	/* enable TIM2 clock */
+	STM32_RCC_APB1ENR |= 0x1;
+
+	/* disable counter during setup */
+	STM32_TIM_CR1(2) = 0x0000;
+
+	/*
+	 * CPU_CLOCK / PSC determines how fast the counter operates.
+	 * ARR determines the wave period, CCRn determines duty cycle.
+	 * Thus, frequency = CPU_CLOCK / PSC / ARR.
+	 *
+	 * Assuming 16MHz clock, the following yields:
+	 * 16MHz / 1600 / 100 = 100Hz.
+	 */
+	STM32_TIM_PSC(2) = CPU_CLOCK / 10000;	/* pre-scaler */
+	STM32_TIM_ARR(2) = 100;			/* auto-reload value */
+	STM32_TIM_CCR2(2) = 100;		/* duty cycle */
+
+	/* CC2 configured as output, PWM mode 1, preload enable */
+	STM32_TIM_CCMR1(2) = (6 << 12) | (1 << 11);
+
+	/* CC2 output enable, active low */
+	STM32_TIM_CCER(2) = (1 << 4) | (1 << 5);
+
+	/* generate update event to force loading of shadow registers */
+	STM32_TIM_EGR(2) |= 1;
+
+	/* enable auto-reload preload, start counting */
+	STM32_TIM_CR1(2) |= (1 << 7) | (1 << 0);
+}
+
+static void power_led_set_duty(int percent)
+{
+	ASSERT((percent >= 0) && (percent <= 100));
+	power_led_percent = percent;
+	STM32_TIM_CCR2(2) = (STM32_TIM_ARR(2) / 100) * percent;
+}
+
+/* returns the timeout period (in us) for current step */
+static int power_led_step(void)
+{
+	int state_timeout = 0;
+	static enum { DOWN = -1, UP = 1 } dir = UP;
+
+	if (0 == power_led_percent) {
+		dir = UP;
+		state_timeout = LED_HOLD_TIME;
+	} else if (100 == power_led_percent) {
+		dir = DOWN;
+		state_timeout = LED_HOLD_TIME;
+	} else {
+		/*
+		 * Decreases timeout as duty cycle percentage approaches
+		 * 0%, increase as it appraoches 100%.
+		 */
+		state_timeout = LED_STATE_TIMEOUT_MIN +
+			LED_STATE_TIMEOUT_MIN * (power_led_percent / 33);
+	}
+
+	/*
+	 * The next duty cycle will take effect after the timeout has
+	 * elapsed for this duty cycle and the power LED task calls this
+	 * function again.
+	 */
+	power_led_set_duty(power_led_percent);
+	power_led_percent += dir * LED_STEP_PERCENT;
+
+	return state_timeout;
+}
+
+void power_led_task(void)
+{
+	power_led_timer_init();
+
+	while (1) {
+		int state_timeout = -1;
+
+		switch (led_state) {
+		case POWERLED_STATE_ON:
+			power_led_set_duty(100);
+			state_timeout = -1;
+			break;
+		case POWERLED_STATE_OFF:
+			power_led_set_duty(0);
+			state_timeout = -1;
+			break;
+		case POWERLED_STATE_SUSPEND:
+			state_timeout = power_led_step();
+			break;
+		default:
+			break;
+		}
+
+		task_wait_event(state_timeout);
+	}
+}
+
+#ifdef CONFIG_CMD_POWERLED
+static int command_powerled(int argc, char **argv)
+{
+	enum powerled_state state = POWERLED_STATE_OFF;
+
+	if (argc != 2)
+		return EC_ERROR_INVAL;
+
+	if (!strcasecmp(argv[1], "off"))
+		state = POWERLED_STATE_OFF;
+	else if (!strcasecmp(argv[1], "on"))
+		state = POWERLED_STATE_ON;
+	else if (!strcasecmp(argv[1], "suspend"))
+		state = POWERLED_STATE_SUSPEND;
+	else
+		return EC_ERROR_INVAL;
+
+	powerled_set_state(state);
+	return EC_SUCCESS;
+}
+DECLARE_CONSOLE_COMMAND(powerled, command_powerled,
+		"[off | on | suspend ]",
+		"Change power LED state",
+		NULL);
+#endif
diff --git a/common/gaia_power.c b/common/gaia_power.c
index efbc4972fd..6f392adf78 100644
--- a/common/gaia_power.c
+++ b/common/gaia_power.c
@@ -28,6 +28,7 @@
 #include "console.h"
 #include "gpio.h"
 #include "keyboard_scan.h"
+#include "power_led.h"
 #include "task.h"
 #include "timer.h"
 #include "util.h"
@@ -101,60 +102,6 @@ static timestamp_t pwron_deadline;
 /* force AP power on (used for recovery keypress) */
 static int auto_power_on;
 
-/*****************************************************************************/
-/* Keyboard power button LED state machine */
-
-/* Suspend mode blinking duty cycle */
-#define LED_OFF_PERIOD  1500000
-#define LED_ON_PERIOD     50000
-
-/* GPIO level for each LED state : it's an active low output */
-#define LED_GPIO_ON   0
-#define LED_GPIO_OFF  1
-
-/* power LED FSM states */
-static enum power_led_state {
-	POWER_LED_OFF,
-	POWER_LED_ON,
-	POWER_LED_SUSP0,
-	POWER_LED_SUSP1,
-
-	POWER_LED_STATE_COUNT
-} led_state;
-
-/* power LED FSM parameters for each state */
-static const struct {
-	int gpio;
-	int duration;
-	enum power_led_state next;
-} led_config[POWER_LED_STATE_COUNT] = {
-	[POWER_LED_OFF]   = {LED_GPIO_OFF, -1,             POWER_LED_OFF},
-	[POWER_LED_ON]    = {LED_GPIO_ON,  -1,             POWER_LED_ON},
-	[POWER_LED_SUSP0] = {LED_GPIO_OFF, LED_OFF_PERIOD, POWER_LED_SUSP1},
-	[POWER_LED_SUSP1] = {LED_GPIO_ON,  LED_ON_PERIOD,  POWER_LED_SUSP0},
-};
-
-static void set_power_led(enum power_led_state new_state)
-{
-	led_state = new_state;
-	/* Wake up the task */
-	task_wake(TASK_ID_POWERLED);
-}
-
-void power_led_task(void)
-{
-	while (1) {
-		int state_timeout;
-
-		gpio_set_level(GPIO_POWER_LED_L, led_config[led_state].gpio);
-		state_timeout = led_config[led_state].duration;
-		led_state = led_config[led_state].next;
-		task_wait_event(state_timeout);
-	}
-}
-
-/*****************************************************************************/
-
 /*
  * Wait for GPIO "signal" to reach level "value".
  * Returns EC_ERROR_TIMEOUT if timeout before reaching the desired state.
@@ -242,7 +189,8 @@ void gaia_suspend_event(enum gpio_signal signal)
 
 	ap_suspended = !gpio_get_level(GPIO_SUSPEND_L);
 
-	set_power_led(ap_suspended ? POWER_LED_SUSP0 : POWER_LED_ON);
+	powerled_set_state(ap_suspended ?
+			POWERLED_STATE_SUSPEND : POWERLED_STATE_ON);
 }
 
 void gaia_power_event(enum gpio_signal signal)
@@ -356,7 +304,7 @@ static int power_on(void)
 	/* Enable 3.3v power rail */
 	gpio_set_level(GPIO_EN_PP3300, 1);
 	ap_on = 1;
-	set_power_led(POWER_LED_ON);
+	powerled_set_state(POWERLED_STATE_ON);
 	CPUTS("AP running ...\n");
 	return 0;
 }
@@ -391,7 +339,7 @@ static void power_off(void)
 	gpio_set_level(GPIO_PMIC_PWRON_L, 1);
 	gpio_set_level(GPIO_EN_PP5000, 0);
 	ap_on = 0;
-	set_power_led(POWER_LED_OFF);
+	powerled_set_state(POWERLED_STATE_OFF);
 	CPUTS("Shutdown complete.\n");
 }
 
diff --git a/include/power_led.h b/include/power_led.h
index 9c8fa49f86..9301a5fdf5 100644
--- a/include/power_led.h
+++ b/include/power_led.h
@@ -18,7 +18,17 @@ enum powerled_color {
 	POWERLED_COLOR_COUNT  /* Number of colors, not a color itself */
 };
 
+enum powerled_state {
+	POWERLED_STATE_OFF,
+	POWERLED_STATE_ON,
+	POWERLED_STATE_SUSPEND,
+	POWERLED_STATE_COUNT
+};
+
 /* Set the power adapter LED to the specified color. */
 int powerled_set(enum powerled_color color);
 
+/* Set the power LED according to the specified state. */
+void powerled_set_state(enum powerled_state state);
+
 #endif  /* __CROS_EC_POWER_LED_H */