pwm: Add a driver for Chrome OS EC PWM
This PWM is used in rk3399-gru-bob and rk3399-gru-kevin to control
the display brightness. We can only change the duty cycle, so on
set_config() we just try to match the duty cycle that dividing duty_ns
by period_ns gives us. To disable, we set the duty cycle to zero while
keeping the old value for when we want to re-enable it.
The cros_ec_set_pwm_duty() function is taken from Depthcharge's
cros_ec_set_bl_pwm_duty() but modified to use the generic pwm type.
The driver itself is very loosely based on rk_pwm.c for the general pwm
driver structure.
The devicetree binding file is from Linux, before it was converted to
YAML at 5df5a577a6b4 ("dt-bindings: pwm: Convert google,cros-ec-pwm.txt
to YAML format") in their repo.
Signed-off-by: Alper Nebi Yasak <alpernebiyasak@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/drivers/pwm/cros_ec_pwm.c b/drivers/pwm/cros_ec_pwm.c
new file mode 100644
index 0000000..44f4105
--- /dev/null
+++ b/drivers/pwm/cros_ec_pwm.c
@@ -0,0 +1,84 @@
+// SPDX-License-Identifier: GPL-2.0+
+
+#include <common.h>
+#include <cros_ec.h>
+#include <dm.h>
+#include <errno.h>
+#include <log.h>
+#include <pwm.h>
+
+struct cros_ec_pwm_priv {
+ bool enabled;
+ uint duty;
+};
+
+static int cros_ec_pwm_set_config(struct udevice *dev, uint channel,
+ uint period_ns, uint duty_ns)
+{
+ struct cros_ec_pwm_priv *priv = dev_get_priv(dev);
+ uint duty;
+ int ret;
+
+ debug("%s: period_ns=%u, duty_ns=%u asked\n", __func__,
+ period_ns, duty_ns);
+
+ /* No way to set the period, only a relative duty cycle */
+ duty = EC_PWM_MAX_DUTY * duty_ns / period_ns;
+ if (duty > EC_PWM_MAX_DUTY)
+ duty = EC_PWM_MAX_DUTY;
+
+ if (!priv->enabled) {
+ priv->duty = duty;
+ debug("%s: duty=%#x to-be-set\n", __func__, duty);
+ return 0;
+ }
+
+ ret = cros_ec_set_pwm_duty(dev->parent, channel, duty);
+ if (ret) {
+ debug("%s: duty=%#x failed\n", __func__, duty);
+ return ret;
+ }
+
+ priv->duty = duty;
+ debug("%s: duty=%#x set\n", __func__, duty);
+
+ return 0;
+}
+
+static int cros_ec_pwm_set_enable(struct udevice *dev, uint channel,
+ bool enable)
+{
+ struct cros_ec_pwm_priv *priv = dev_get_priv(dev);
+ int ret;
+
+ ret = cros_ec_set_pwm_duty(dev->parent, channel,
+ enable ? priv->duty : 0);
+ if (ret) {
+ debug("%s: enable=%d failed\n", __func__, enable);
+ return ret;
+ }
+
+ priv->enabled = enable;
+ debug("%s: enable=%d (duty=%#x) set\n", __func__,
+ enable, priv->duty);
+
+ return 0;
+}
+
+static const struct pwm_ops cros_ec_pwm_ops = {
+ .set_config = cros_ec_pwm_set_config,
+ .set_enable = cros_ec_pwm_set_enable,
+};
+
+static const struct udevice_id cros_ec_pwm_ids[] = {
+ { .compatible = "google,cros-ec-pwm" },
+ { }
+};
+
+U_BOOT_DRIVER(cros_ec_pwm) = {
+ .name = "cros_ec_pwm",
+ .id = UCLASS_PWM,
+ .of_match = cros_ec_pwm_ids,
+ .ops = &cros_ec_pwm_ops,
+ .priv_auto_alloc_size = sizeof(struct cros_ec_pwm_priv),
+};