[nrf fromlist] drivers: serial: nrfx_uarte: Minor code size optimization

Optimize function which enables UARTE peripheral. It is called
only when interrupts are locked so data->flags does not require
atomic operation. Use standard logical operations so save few
bytes.

Upstream PR: zephyrproject-rtos/zephyr#80201

Signed-off-by: Krzysztof Chruściński <[email protected]>

Author: nordic-krch

drivers/serial/uart_nrfx_uarte.c

@@ -218,6 +218,7 @@ struct uarte_nrfx_data {
 
 #define UARTE_FLAG_LOW_POWER_TX BIT(0)
 #define UARTE_FLAG_LOW_POWER_RX BIT(1)
+#define UARTE_FLAG_LOW_POWER (UARTE_FLAG_LOW_POWER_TX | UARTE_FLAG_LOW_POWER_RX)
 #define UARTE_FLAG_TRIG_RXTO BIT(2)
 #define UARTE_FLAG_POLL_OUT BIT(3)
 
@@ -613,11 +614,13 @@ static void uarte_periph_enable(const struct device *dev)
 	}
 }
 
-static void uarte_enable(const struct device *dev, uint32_t act_mask, uint32_t sec_mask)
+static void uarte_enable_locked(const struct device *dev, uint32_t act_mask, uint32_t sec_mask)
 {
 	struct uarte_nrfx_data *data = dev->data;
+	bool already_active = (data->flags & UARTE_FLAG_LOW_POWER) != 0;
 
-	if (atomic_or(&data->flags, act_mask) & sec_mask) {
+	data->flags |= act_mask;
+	if (already_active) {
 		/* Second direction already enabled so UARTE is enabled. */
 		return;
 	}
@@ -653,7 +656,7 @@ static void tx_start(const struct device *dev, const uint8_t *buf, size_t len)
 	nrf_uarte_event_clear(uarte, NRF_UARTE_EVENT_TXSTOPPED);
 
 	if (LOW_POWER_ENABLED(config)) {
-		uarte_enable(dev, UARTE_FLAG_LOW_POWER_TX, UARTE_FLAG_LOW_POWER_RX);
+		uarte_enable_locked(dev, UARTE_FLAG_LOW_POWER_TX, UARTE_FLAG_LOW_POWER_RX);
 	}
 
 	nrf_uarte_task_trigger(uarte, NRF_UARTE_TASK_STARTTX);
@@ -1154,7 +1157,7 @@ static int uarte_nrfx_rx_enable(const struct device *dev, uint8_t *buf,
 	} else if (LOW_POWER_ENABLED(cfg)) {
 		unsigned int key = irq_lock();
 
-		uarte_enable(dev, UARTE_FLAG_LOW_POWER_RX, UARTE_FLAG_LOW_POWER_TX);
+		uarte_enable_locked(dev, UARTE_FLAG_LOW_POWER_RX, UARTE_FLAG_LOW_POWER_TX);
 		irq_unlock(key);
 	}