mailbox: pcc: Refactor error handling in irq handler into separate function

The existing error handling logic in pcc_mbox_irq() is intermixed with the
main flow of the function. The command complete check and the complete
complete update/acknowledgment are nicely factored into separate functions.

Moves error detection and clearing logic into a separate function called:
pcc_mbox_error_check_and_clear() by extracting error-handling logic from
pcc_mbox_irq().

This ensures error checking and clearing are handled separately and it
improves maintainability by keeping the IRQ handler focused on processing
events.

Acked-by: Huisong Li <lihuisong@huawei.com>
Tested-by: Huisong Li <lihuisong@huawei.com>
Tested-by: Adam Young <admiyo@os.amperecomputing.com>
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
Signed-off-by: Jassi Brar <jassisinghbrar@gmail.com>

Author: sudeep-holla

drivers/mailbox/pcc.c

@@ -269,6 +269,25 @@ static bool pcc_mbox_cmd_complete_check(struct pcc_chan_info *pchan)
 	return !!val;
 }
 
+static int pcc_mbox_error_check_and_clear(struct pcc_chan_info *pchan)
+{
+	u64 val;
+	int ret;
+
+	ret = pcc_chan_reg_read(&pchan->error, &val);
+	if (ret)
+		return ret;
+
+	val &= pchan->error.status_mask;
+	if (val) {
+		val &= ~pchan->error.status_mask;
+		pcc_chan_reg_write(&pchan->error, val);
+		return -EIO;
+	}
+
+	return 0;
+}
+
 static void check_and_ack(struct pcc_chan_info *pchan, struct mbox_chan *chan)
 {
 	struct acpi_pcct_ext_pcc_shared_memory pcc_hdr;
@@ -309,8 +328,6 @@ static irqreturn_t pcc_mbox_irq(int irq, void *p)
 {
 	struct pcc_chan_info *pchan;
 	struct mbox_chan *chan = p;
-	u64 val;
-	int ret;
 
 	pchan = chan->con_priv;
 
@@ -324,15 +341,8 @@ static irqreturn_t pcc_mbox_irq(int irq, void *p)
 	if (!pcc_mbox_cmd_complete_check(pchan))
 		return IRQ_NONE;
 
-	ret = pcc_chan_reg_read(&pchan->error, &val);
-	if (ret)
+	if (pcc_mbox_error_check_and_clear(pchan))
 		return IRQ_NONE;
-	val &= pchan->error.status_mask;
-	if (val) {
-		val &= ~pchan->error.status_mask;
-		pcc_chan_reg_write(&pchan->error, val);
-		return IRQ_NONE;
-	}
 
 	/*
 	 * Clear this flag after updating interrupt ack register and just