drivers: serial: uart_mcux_lpuart: Fix pinctrl flow control

Currently the driver code does not actually request the flow control
state, it only checks if the state exists. To fix this we should
simply call pinctrl_apply_state() and if that fails, meaning no
flow control state exists, fall back to default pin mux settings.

Another case that needed fixing is run time flow control enabling
ie in the case where we have a WIFI/bluetooth module connected
and we initially operate without flow control but later enable
it after firmware download.

This patch addresses this as well by making a generic function
to achieve this.

Signed-off-by: Bas van Loon <[email protected]>

Author: bas-archembedded

drivers/serial/uart_mcux_lpuart.c

@@ -974,9 +974,31 @@ static void mcux_lpuart_isr(const struct device *dev)
 }
 #endif /* CONFIG_UART_MCUX_LPUART_ISR_SUPPORT */
 
+static int mcux_lpuart_config_pinctrl(const struct device *dev, uint8_t flow_ctrl)
+{
+	const struct mcux_lpuart_config *config = dev->config;
+	int err;
+
+	if (flow_ctrl) {
+		err = pinctrl_apply_state(config->pincfg, PINCTRL_STATE_FLOWCONTROL);
+		if (err < 0) {
+			LOG_WRN("Failed to set flowcontrol state, using default state");
+			/* Fallback to default state if flow-control pins are not set */
+			err = pinctrl_apply_state(config->pincfg, PINCTRL_STATE_DEFAULT);
+		}
+	} else {
+		err = pinctrl_apply_state(config->pincfg, PINCTRL_STATE_DEFAULT);
+	}
+
+	return err;
+}
+
 #if LPUART_HAS_MODEM
-static int mcux_lpuart_config_flowctrl(uint8_t flow_ctrl, lpuart_config_t *uart_config)
+static int mcux_lpuart_config_flowctrl(const struct device *dev, uint8_t flow_ctrl,
+				       lpuart_config_t *uart_config)
 {
+	int ret = 0;
+
 	switch (flow_ctrl) {
 	case UART_CFG_FLOW_CTRL_NONE:
 	case UART_CFG_FLOW_CTRL_RS485:
@@ -990,13 +1012,20 @@ static int mcux_lpuart_config_flowctrl(uint8_t flow_ctrl, lpuart_config_t *uart_
 		break;
 
 	default:
-		return -ENOTSUP;
+		ret = -ENOTSUP;
+		break;
 	}
 
-	return 0;
+	if (ret == 0) {
+		/* Configure the pinctrl for flow control */
+		ret = mcux_lpuart_config_pinctrl(dev, flow_ctrl);
+	}
+
+	return ret;
 }
 #else
-static int mcux_lpuart_config_flowctrl(uint8_t flow_ctrl, lpuart_config_t *uart_config)
+static int mcux_lpuart_config_flowctrl(const struct device *dev, uint8_t flow_ctrl,
+				       lpuart_config_t *uart_config)
 {
 	if (flow_ctrl != UART_CFG_FLOW_CTRL_NONE) {
 		return -ENOTSUP;
@@ -1059,7 +1088,7 @@ static int mcux_lpuart_configure_basic(const struct device *dev, const struct ua
 		return -ENOTSUP;
 	}
 
-	ret = mcux_lpuart_config_flowctrl(cfg->flow_ctrl, uart_config);
+	ret = mcux_lpuart_config_flowctrl(dev, cfg->flow_ctrl, uart_config);
 	if (ret) {
 		return ret;
 	}
@@ -1322,16 +1351,7 @@ static int mcux_lpuart_init(const struct device *dev)
 
 	/* set initial configuration */
 	mcux_lpuart_configure_init(dev, uart_api_config);
-	if (config->flow_ctrl) {
-		const struct pinctrl_state *state;
-
-		err = pinctrl_lookup_state(config->pincfg, PINCTRL_STATE_FLOWCONTROL, &state);
-		if (err < 0) {
-			err = pinctrl_apply_state(config->pincfg, PINCTRL_STATE_DEFAULT);
-		}
-	} else {
-		err = pinctrl_apply_state(config->pincfg, PINCTRL_STATE_DEFAULT);
-	}
+	err = mcux_lpuart_config_pinctrl(dev, config->flow_ctrl);
 	if (err < 0) {
 		return err;
 	}