spring: Implement PWM control on ILIM_500

This adds init code to configure PWM and a console command to adjust
duty cycle.
Also rename ILIM_1500 to BOOST_EN.

BUG=chrome-os-partner:14319
TEST=Adjust PWM duty cycle and measure voltage.
BRANCH=none

Change-Id: I23856416da19ed523d46af39e6cbc3129ac25525
Signed-off-by: Vic Yang <victoryang@chromium.org>
Reviewed-on: https://gerrit.chromium.org/gerrit/39587

4 files changed, 102 insertions, 5 deletions

diff --git a/board/spring/board.c b/board/spring/board.c
index 9316aaad52..4e4ddd1395 100644
--- a/board/spring/board.c
+++ b/board/spring/board.c
@@ -92,8 +92,7 @@ const struct gpio_info gpio_list[GPIO_COUNT] = {
 	{"KB_OUT10",    GPIO_C, (1<<5),  GPIO_KB_OUTPUT, NULL},
 	{"KB_OUT11",    GPIO_C, (1<<6),  GPIO_KB_OUTPUT, NULL},
 	{"KB_OUT12",    GPIO_C, (1<<7),  GPIO_KB_OUTPUT, NULL},
-	{"ILIM_1500",   GPIO_B, (1<<3),  GPIO_OUT_HIGH, NULL},
-	{"ILIM_500",    GPIO_B, (1<<4),  GPIO_OUT_LOW, NULL},
+	{"BOOST_EN",    GPIO_B, (1<<3),  GPIO_OUT_HIGH, NULL},
 };
 
 /* ADC channels */
@@ -127,6 +126,13 @@ void configure_board(void)
 	STM32_GPIO_AFIO_MAPR = (STM32_GPIO_AFIO_MAPR & ~(0x7 << 24))
 			       | (4 << 24);
 
+	/* remap TIM3_CH1 to PB4 */
+	STM32_GPIO_AFIO_MAPR = (STM32_GPIO_AFIO_MAPR & ~(0x3 << 10))
+			       | (2 << 10);
+
+	/* Set up PWM on TIM3 */
+	board_configure_pwm();
+
 	/*
 	 * Set alternate function for USART1. For alt. function input
 	 * the port is configured in either floating or pull-up/down
diff --git a/board/spring/board.h b/board/spring/board.h
index e4c0e27e64..6b99e9c5cb 100644
--- a/board/spring/board.h
+++ b/board/spring/board.h
@@ -121,8 +121,7 @@ enum gpio_signal {
 	GPIO_KB_OUT10,
 	GPIO_KB_OUT11,
 	GPIO_KB_OUT12,
-	GPIO_ILIM_1500,        /* max charging current : 1500 mA */
-	GPIO_ILIM_500,         /* max charging current :  500 mA */
+	GPIO_BOOST_EN,
 	/* Number of GPIOs; not an actual GPIO */
 	GPIO_COUNT
 };
@@ -140,6 +139,12 @@ int board_pmu_init(void);
 /* Force the pmu to reset everything on the board */
 void board_hard_reset(void);
 
+/* Set up PWM for ILIM */
+void board_configure_pwm(void);
+
+/* Set PWM duty cycle */
+void board_pwm_duty_cycle(int percent);
+
 #endif /* !__ASSEMBLER__ */
 
 #endif /* __BOARD_H */
diff --git a/board/spring/build.mk b/board/spring/build.mk
index ae15fbe081..bb6f4ae234 100644
--- a/board/spring/build.mk
+++ b/board/spring/build.mk
@@ -8,4 +8,4 @@
 CHIP:=stm32
 CHIP_VARIANT:=stm32f100
 
-board-y=board.o
+board-y=board.o usb_charging.o
diff --git a/board/spring/usb_charging.c b/board/spring/usb_charging.c
new file mode 100644
index 0000000000..3f93fe6e72
--- /dev/null
+++ b/board/spring/usb_charging.c
@@ -0,0 +1,86 @@
+/* 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.
+ */
+
+/* USB charging control for spring board */
+
+#include "board.h"
+#include "console.h"
+#include "registers.h"
+#include "util.h"
+
+#define PWM_FREQUENCY 100 /* Hz */
+
+void board_configure_pwm(void)
+{
+	uint32_t val;
+
+	/* Config alt. function (TIM3/PWM) */
+	val = STM32_GPIO_CRL_OFF(GPIO_B) & ~0x000f0000;
+	val |= 0x00090000;
+	STM32_GPIO_CRL_OFF(GPIO_B) = val;
+
+	/* Enable TIM3 clock */
+	STM32_RCC_APB1ENR |= 0x2;
+
+	/* Disable counter during setup */
+	STM32_TIM_CR1(3) = 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 and ARR=100, PSC needed to achieve PWM_FREQUENCY
+	 * is: PSC = CPU_CLOCK / PWM_FREQUENCY / ARR
+	 */
+	STM32_TIM_PSC(3) = CPU_CLOCK / PWM_FREQUENCY / 100; /* pre-scaler */
+	STM32_TIM_ARR(3) = 100;			/* auto-reload value */
+	STM32_TIM_CCR1(3) = 100;		/* duty cycle */
+
+	/* CC1 configured as output, PWM mode 1, preload enable */
+	STM32_TIM_CCMR1(3) = (6 << 4) | (1 << 3);
+
+	/* CC1 output enable, active high */
+	STM32_TIM_CCER(3) = (1 << 0);
+
+	/* Generate update event to force loading of shadow registers */
+	STM32_TIM_EGR(3) |= 1;
+
+	/* Enable auto-reload preload, start counting */
+	STM32_TIM_CR1(3) |= (1 << 7) | (1 << 0);
+}
+
+void board_pwm_duty_cycle(int percent)
+{
+	if (percent < 0)
+		percent = 0;
+	if (percent > 100)
+		percent = 100;
+	STM32_TIM_CCR1(3) = (percent * STM32_TIM_ARR(3)) / 100;
+}
+
+/*
+ * Console command for debugging.
+ * TODO(victoryang): Remove after charging control is done.
+ */
+static int command_ilim(int argc, char **argv)
+{
+	char *e;
+	int percent;
+
+	if (argc >= 2) {
+		percent = strtoi(argv[1], &e, 0);
+		if (*e)
+			return EC_ERROR_PARAM1;
+		board_pwm_duty_cycle(percent);
+	}
+	ccprintf("PWM duty cycle set to %d%%\n", STM32_TIM_CCR1(3));
+
+	return EC_SUCCESS;
+}
+DECLARE_CONSOLE_COMMAND(ilim, command_ilim,
+		"[percent]",
+		"Set or show ILIM duty cycle",
+		NULL);