[PATCH 1/2] mailbox: Propagate errors from .send_data() callback to mbox_send_message()

[Evgenii Shatokhin <e.shatokhin@yadro.com>]

msg_submit() calls .send_data() function from the mailbox controller driver
to place the first of the queued messages to the mailbox. Depending on the
actual driver used, this operation could fail.

In this case, if mbox_send_message() is called in blocking mode, it will
always return -ETIME rather than the actual error reported by the
underlying driver. This could be confusing, so let us propagate the
error from msg_submit() to mbox_send_message().

The errors from msg_submit() called in tx_tick() should be handled in a
subsequent patch.

Signed-off-by: Evgenii Shatokhin <e.shatokhin@yadro.com>
---
 drivers/mailbox/mailbox.c | 19 ++++++++++++++-----
 1 file changed, 14 insertions(+), 5 deletions(-)

diff --git a/drivers/mailbox/mailbox.c b/drivers/mailbox/mailbox.c
index 4229b9b5da98..04db5ef58f93 100644
--- a/drivers/mailbox/mailbox.c
+++ b/drivers/mailbox/mailbox.c
@@ -50,17 +50,24 @@ static int add_to_rbuf(struct mbox_chan *chan, void *mssg)
 	return idx;
 }
 
-static void msg_submit(struct mbox_chan *chan)
+static int msg_submit(struct mbox_chan *chan)
 {
 	unsigned count, idx;
 	unsigned long flags;
 	void *data;
-	int err = -EBUSY;
+	int err = 0;
 
 	spin_lock_irqsave(&chan->lock, flags);
 
-	if (!chan->msg_count || chan->active_req)
+	if (!chan->msg_count) {
+		spin_unlock_irqrestore(&chan->lock, flags);
+		return 0;
+	}
+
+	if (chan->active_req) {
+		err = -EBUSY;
 		goto exit;
+	}
 
 	count = chan->msg_count;
 	idx = chan->msg_free;
@@ -88,6 +95,7 @@ static void msg_submit(struct mbox_chan *chan)
 		hrtimer_start(&chan->mbox->poll_hrt, 0, HRTIMER_MODE_REL);
 		spin_unlock_irqrestore(&chan->mbox->poll_hrt_lock, flags);
 	}
+	return err;
 }
 
 static void tx_tick(struct mbox_chan *chan, int r)
@@ -256,6 +264,7 @@ EXPORT_SYMBOL_GPL(mbox_client_peek_data);
 int mbox_send_message(struct mbox_chan *chan, void *mssg)
 {
 	int t;
+	int err;
 
 	if (!chan || !chan->cl)
 		return -EINVAL;
@@ -266,7 +275,7 @@ int mbox_send_message(struct mbox_chan *chan, void *mssg)
 		return t;
 	}
 
-	msg_submit(chan);
+	err = msg_submit(chan);
 
 	if (chan->cl->tx_block) {
 		unsigned long wait;
@@ -284,7 +293,7 @@ int mbox_send_message(struct mbox_chan *chan, void *mssg)
 		}
 	}
 
-	return t;
+	return (err < 0) ? err : t;
 }
 EXPORT_SYMBOL_GPL(mbox_send_message);
 
-- 
2.34.1