mailbox: mpfs: switch to txdone_poll

The system controller on PolarFire SoC has no interrupt to signify that
the TX has been completed. The interrupt instead signals that a service
requested by the mailbox client has succeeded. If a service fails, there
will be no interrupt delivered.

Switch to polling the busy register to determine whether transmission
has completed.

Fixes: 83d7b15 ("mbox: add polarfire soc system controller mailbox")
Acked-by: Jassi Brar <jaswinder.singh@linaro.org>
Tested-by: Valentina Fernandez <valentina.fernandezalanis@microchip.com>
Signed-off-by: Conor Dooley <conor.dooley@microchip.com>

Author: ConchuOD

drivers/mailbox/mailbox-mpfs.c

@@ -79,6 +79,13 @@ static bool mpfs_mbox_busy(struct mpfs_mbox *mbox)
 	return status & SCB_STATUS_BUSY_MASK;
 }
 
+static bool mpfs_mbox_last_tx_done(struct mbox_chan *chan)
+{
+	struct mpfs_mbox *mbox = (struct mpfs_mbox *)chan->con_priv;
+
+	return !mpfs_mbox_busy(mbox);
+}
+
 static int mpfs_mbox_send_data(struct mbox_chan *chan, void *data)
 {
 	struct mpfs_mbox *mbox = (struct mpfs_mbox *)chan->con_priv;
@@ -183,7 +190,6 @@ static irqreturn_t mpfs_mbox_inbox_isr(int irq, void *data)
 
 	mpfs_mbox_rx_data(chan);
 
-	mbox_chan_txdone(chan, 0);
 	return IRQ_HANDLED;
 }
 
@@ -213,6 +219,7 @@ static const struct mbox_chan_ops mpfs_mbox_ops = {
 	.send_data = mpfs_mbox_send_data,
 	.startup = mpfs_mbox_startup,
 	.shutdown = mpfs_mbox_shutdown,
+	.last_tx_done = mpfs_mbox_last_tx_done,
 };
 
 static int mpfs_mbox_probe(struct platform_device *pdev)
@@ -248,7 +255,8 @@ static int mpfs_mbox_probe(struct platform_device *pdev)
 	mbox->controller.num_chans = 1;
 	mbox->controller.chans = mbox->chans;
 	mbox->controller.ops = &mpfs_mbox_ops;
-	mbox->controller.txdone_irq = true;
+	mbox->controller.txdone_poll = true;
+	mbox->controller.txpoll_period = 10u;
 
 	ret = devm_mbox_controller_register(&pdev->dev, &mbox->controller);
 	if (ret) {