drivers: mbox: imx_mu: change order of interrupt handling

Handle notification interrupt before data interrupt of
a channel. Notification interrupts are more commonly
used (e.g. for ipc) and clearing the interrupt ASAP
helps reduce the possiblility that the sender finds
the interrupt already pending if it tries to send multiple
ipc messages in quick succession.

Signed-off-by: Mike J. Chen <[email protected]>

Author: mjchen0

drivers/mbox/mbox_nxp_imx_mu.c

@@ -184,9 +184,25 @@ static void mu_isr(const struct device *dev)
 	const uint32_t flags = MU_GetStatusFlags(config->base);
 
 	for (int i_channel = 0; i_channel < MU_MAX_CHANNELS; i_channel++) {
-		const uint32_t rx_int_mask = g_rx_flag_mask[i_channel];
+		/* Handle notification interrupt for the channel first and
+		 * then handle the data ready interrupt for the channel.
+		 * Notification interrupts are more commonly used (e.g. for
+		 * ipc) and clearing the interrupt ASAP reduces the chance
+		 * the other side gets an error when pending a new interrupt
+		 * if it is sending multiple IPC messages in quick succession.
+		 */
 		const uint32_t gen_int_mask = g_gen_int_pend_mask[i_channel];
 
+		if ((flags & gen_int_mask) == gen_int_mask) {
+			MU_ClearStatusFlags(config->base, gen_int_mask);
+			if (data->cb[i_channel]) {
+				data->cb[i_channel](dev, i_channel, data->user_data[i_channel],
+						    NULL);
+			}
+		}
+
+		const uint32_t rx_int_mask = g_rx_flag_mask[i_channel];
+
 		if ((flags & rx_int_mask) == rx_int_mask) {
 			data->received_data = MU_ReceiveMsgNonBlocking(config->base, i_channel);
 			struct mbox_msg msg = {(const void *)&data->received_data, MU_MBOX_SIZE};
@@ -196,13 +212,5 @@ static void mu_isr(const struct device *dev)
 						    &msg);
 			}
 		}
-		if ((flags & gen_int_mask) == gen_int_mask) {
-			MU_ClearStatusFlags(config->base, gen_int_mask);
-			if (data->cb[i_channel]) {
-				data->cb[i_channel](dev, i_channel, data->user_data[i_channel],
-						    NULL);
-			}
-		}
-
 	}
 }