zephyr: add PWM shim

Adds PWM shim to connect the platform/ec PWM API to the Zephyr PWM API.

BUG=b:174850923
BRANCH=none
TEST=make buildall
TEST=Run "pwmduty" command against Volteer LEDs

Signed-off-by: Keith Short <keithshort@chromium.org>
Change-Id: I49047734bc1a3fb3d4010f0040145171275c5657
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/2623163
Reviewed-by: Jack Rosenthal <jrosenth@chromium.org>

2 files changed, 188 insertions, 0 deletions

diff --git a/zephyr/shim/src/CMakeLists.txt b/zephyr/shim/src/CMakeLists.txt
index 6512938e56..1a4a75025e 100644
--- a/zephyr/shim/src/CMakeLists.txt
+++ b/zephyr/shim/src/CMakeLists.txt
@@ -15,6 +15,7 @@ zephyr_sources_ifdef(CONFIG_PLATFORM_EC_HOOKS       hooks.c)
 zephyr_sources_ifdef(CONFIG_PLATFORM_EC_HOSTCMD     host_command.c)
 zephyr_sources_ifdef(CONFIG_PLATFORM_EC_MKBP_EVENT  mkbp_event.c)
 zephyr_sources_ifdef(CONFIG_PLATFORM_EC_PANIC       panic.c)
+zephyr_sources_ifdef(CONFIG_PLATFORM_EC_PWM         pwm.c)
 zephyr_sources_ifdef(CONFIG_PLATFORM_EC_TIMER       hwtimer.c)
 zephyr_sources_ifdef(CONFIG_PLATFORM_EC_I2C         i2c.c)
 zephyr_sources_ifdef(CONFIG_CROS_EC                 system.c)
diff --git a/zephyr/shim/src/pwm.c b/zephyr/shim/src/pwm.c
new file mode 100644
index 0000000000..a9466684d6
--- /dev/null
+++ b/zephyr/shim/src/pwm.c
@@ -0,0 +1,187 @@
+/* Copyright 2021 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.
+ */
+
+#include <device.h>
+#include <devicetree.h>
+#include <drivers/pwm.h>
+#include <logging/log.h>
+
+#include "common.h"
+#include "console.h"
+#include "ec_commands.h"
+#include "pwm.h"
+#include "util.h"
+
+#include "pwm/pwm.h"
+
+LOG_MODULE_REGISTER(pwm_shim, LOG_LEVEL_ERR);
+
+#define USECS_PER_SEC 1000000
+
+/*
+ * Initialize the device bindings in pwm_channels.
+ * This macro is called from within DT_FOREACH_CHILD
+ */
+#define INIT_DEV_BINDING(id) {                                              \
+		pwm_configs[PWM_CHANNEL(id)].name = DT_LABEL(id);           \
+		pwm_configs[PWM_CHANNEL(id)].dev = device_get_binding(      \
+			DT_PROP_BY_PHANDLE(id, pwms, label));               \
+		pwm_configs[PWM_CHANNEL(id)].pin = DT_PWMS_CHANNEL(id);     \
+		pwm_configs[PWM_CHANNEL(id)].flags = DT_PWMS_FLAGS(id);     \
+		pwm_configs[PWM_CHANNEL(id)].freq = DT_PROP(id, frequency); \
+	}
+
+struct pwm_config {
+	/* Name */
+	const char *name;
+	/* PWM pin */
+	uint32_t pin;
+	/* PWM channel flags. See dt-bindings/pwm/pwm.h */
+	pwm_flags_t flags;
+	/* PWM operating frequency. Configured by the devicetree */
+	uint32_t freq;
+
+	/* PWM period in microseconds. Automatically set to 1/frequency */
+	uint32_t period_us;
+	/* PWM pulse in microseconds. Set by pwm_set_raw_duty */
+	uint32_t pulse_us;
+	/* Saves whether the PWM channel is currently enabled */
+	bool enabled;
+
+	/* Runtime device for PWM */
+	const struct device *dev;
+};
+
+static struct pwm_config pwm_configs[PWM_CH_COUNT];
+
+static int init_pwms(const struct device *unused)
+{
+	struct pwm_config *pwm;
+	int rv = 0;
+
+	ARG_UNUSED(unused);
+
+	/* Initialize PWM data from the device tree */
+	DT_FOREACH_CHILD(DT_PATH(named_pwms), INIT_DEV_BINDING)
+
+	/* Read the PWM operating frequency, set by the chip driver */
+	for (size_t i = 0; i < PWM_CH_COUNT; ++i) {
+		pwm = &pwm_configs[i];
+
+		if (pwm->dev == NULL) {
+			LOG_ERR("Not found (%s)", pwm->name);
+			rv = -ENODEV;
+			continue;
+		}
+
+		/*
+		 * TODO - check that devicetree frequency is less than 1/2
+		 * max frequency from the chip driver.
+		 */
+		pwm->period_us = USECS_PER_SEC / pwm->freq;
+	}
+
+	return rv;
+}
+SYS_INIT(init_pwms, PRE_KERNEL_1, 50);
+
+static struct pwm_config* pwm_lookup(enum pwm_channel ch)
+{
+	__ASSERT(ch < ARRAY_SIZE(pwm_configs), "Invalid PWM channel %d", ch);
+
+	return &pwm_configs[ch];
+}
+
+void pwm_enable(enum pwm_channel ch, int enabled)
+{
+	struct pwm_config *pwm;
+	uint32_t pulse_us;
+	int rv;
+
+	pwm = pwm_lookup(ch);
+	pwm->enabled = enabled;
+
+	/*
+	 * The Zephyr API doesn't provide explicit enable and disable
+	 * commands. However, setting the pulse width to zero disables
+	 * the PWM.
+	 */
+	if (enabled)
+		pulse_us = pwm->pulse_us;
+	else
+		pulse_us = 0;
+
+	rv = pwm_pin_set_usec(pwm->dev, pwm->pin, pwm->period_us, pulse_us,
+			      pwm->flags);
+
+	if (rv)
+		LOG_ERR("pwm_pin_set_usec() failed %s (%d)", pwm->name, rv);
+}
+
+int pwm_get_enabled(enum pwm_channel ch)
+{
+	struct pwm_config *pwm;
+
+	pwm = pwm_lookup(ch);
+	return pwm->enabled;
+}
+
+void pwm_set_raw_duty(enum pwm_channel ch, uint16_t duty)
+{
+	struct pwm_config *pwm;
+	int rv;
+
+	pwm = pwm_lookup(ch);
+
+	pwm->pulse_us =
+		DIV_ROUND_NEAREST(pwm->period_us * duty, EC_PWM_MAX_DUTY);
+
+	LOG_DBG("PWM %s set raw duty (0x%04x), pulse %d", pwm->name, duty,
+		pwm->pulse_us);
+
+	rv = pwm_pin_set_usec(pwm->dev, pwm->pin, pwm->period_us, pwm->pulse_us,
+			      pwm->flags);
+
+	if (rv)
+		LOG_ERR("pwm_pin_set_usec() failed %s (%d)", pwm->name, rv);
+}
+
+uint16_t pwm_get_raw_duty(enum pwm_channel ch)
+{
+	struct pwm_config *pwm;
+
+	pwm = pwm_lookup(ch);
+
+	return DIV_ROUND_NEAREST(pwm->pulse_us * EC_PWM_MAX_DUTY,
+				 pwm->period_us);
+}
+
+void pwm_set_duty(enum pwm_channel ch, int percent)
+{
+	struct pwm_config *pwm;
+	int rv;
+
+	pwm = pwm_lookup(ch);
+
+	pwm->pulse_us = DIV_ROUND_NEAREST(pwm->period_us * percent, 100);
+
+	LOG_DBG("PWM %s set percent (%d), pulse %d", pwm->name, percent,
+		pwm->pulse_us);
+
+	rv = pwm_pin_set_usec(pwm->dev, pwm->pin, pwm->period_us, pwm->pulse_us,
+			      pwm->flags);
+
+	if (rv)
+		LOG_ERR("pwm_pin_set_usec() failed %s (%d)", pwm->name, rv);
+}
+
+int pwm_get_duty(enum pwm_channel ch)
+{
+	struct pwm_config *pwm;
+
+	pwm = pwm_lookup(ch);
+
+	return DIV_ROUND_NEAREST(pwm->pulse_us * 100, pwm->period_us);
+}