1 files changed, 86 insertions, 0 deletions
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);