drivers: serial: lpuart: Add support for CCM rev3

Since the nxp,imx-ccm-rev3 binding also lets the user specify
the frequency for the IP clock, the LPUART driver needs to be
updated such that it can make use of the frequency specified
in the DTS.

Signed-off-by: Laurentiu Mihalcea <[email protected]>

drivers/serial/uart_mcux_lpuart.c

@@ -37,6 +37,7 @@ struct mcux_lpuart_config {
 	const struct device *clock_dev;
 	const struct pinctrl_dev_config *pincfg;
 	clock_control_subsys_t clock_subsys;
+	clock_control_subsys_rate_t clock_freq;
 	uint32_t baud_rate;
 	uint8_t flow_ctrl;
 	uint8_t parity;
@@ -885,16 +886,32 @@ static int mcux_lpuart_configure_init(const struct device *dev, const struct uar
 	const struct mcux_lpuart_config *config = dev->config;
 	struct mcux_lpuart_data *data = dev->data;
 	uint32_t clock_freq;
+	int ret;
 
 	if (!device_is_ready(config->clock_dev)) {
 		return -ENODEV;
 	}
 
-	if (clock_control_get_rate(config->clock_dev, config->clock_subsys,
-				   &clock_freq)) {
+	ret = clock_control_off(config->clock_dev, config->clock_subsys);
+	if (ret < 0)
 		return -EINVAL;
+
+	if (config->clock_freq) {
+		ret = clock_control_set_rate(config->clock_dev,
+				config->clock_subsys, config->clock_freq);
+		if (ret < 0 && ret != -EALREADY)
+			return ret;
 	}
 
+	ret = clock_control_get_rate(config->clock_dev, config->clock_subsys, &clock_freq);
+	if (ret < 0)
+		return -EINVAL;
+
+	ret = clock_control_on(config->clock_dev, config->clock_subsys);
+	if (ret < 0)
+		return -EINVAL;
+
+
 	lpuart_config_t uart_config;
 	LPUART_GetDefaultConfig(&uart_config);
 
@@ -1185,11 +1202,18 @@ static const struct uart_driver_api mcux_lpuart_driver_api = {
 				? UART_CFG_FLOW_CTRL_RS485   \
 				: UART_CFG_FLOW_CTRL_NONE
 
+#ifdef CONFIG_CLOCK_CONTROL_MCUX_CCM_REV3
+#define CLOCK_FREQ(inst) DT_INST_CLOCKS_CELL(inst, freq)
+#else
+#define CLOCK_FREQ(inst) 0
+#endif /* CONFIG_CLOCK_CONTROL_MCUX_CCM_REV3 */
+
 #define LPUART_MCUX_DECLARE_CFG(n)                                      \
 static const struct mcux_lpuart_config mcux_lpuart_##n##_config = {     \
 	.base = (LPUART_Type *) DT_INST_REG_ADDR(n),                          \
 	.clock_dev = DEVICE_DT_GET(DT_INST_CLOCKS_CTLR(n)),                   \
 	.clock_subsys = (clock_control_subsys_t)DT_INST_CLOCKS_CELL(n, name),	\
+	.clock_freq = (clock_control_subsys_rate_t)CLOCK_FREQ(n),             \
 	.baud_rate = DT_INST_PROP(n, current_speed),                          \
 	.flow_ctrl = FLOW_CONTROL(n),                                         \
 	.parity = DT_INST_ENUM_IDX_OR(n, parity, UART_CFG_PARITY_NONE),       \