openwrt/target/linux/generic/patches-3.18/092-01-spi-Check-to-see-if-the-device-is-processing-a-messa.patch

From: Mark Brown <broonie@kernel.org>
Date: Tue, 9 Dec 2014 19:46:56 +0000
Subject: [PATCH] spi: Check to see if the device is processing a message
 before we idle

cur_msg is updated under the queue lock and holds the message we are
currently processing. Since currently we only ever do removals in the
pump kthread it doesn't matter in what order we do things but we want
to be able to push things out from the submitting thread so pull the
check to see if we're currently handling a message before we check to
see if the queue is idle.

Signed-off-by: Mark Brown <broonie@kernel.org>
---

--- a/drivers/spi/spi.c
+++ b/drivers/spi/spi.c
@@ -891,8 +891,16 @@ static void spi_pump_messages(struct kth
 	bool was_busy = false;
 	int ret;
 
-	/* Lock queue and check for queue work */
+	/* Lock queue */
 	spin_lock_irqsave(&master->queue_lock, flags);
+
+	/* Make sure we are not already running a message */
+	if (master->cur_msg) {
+		spin_unlock_irqrestore(&master->queue_lock, flags);
+		return;
+	}
+
+	/* Check if the queue is idle */
 	if (list_empty(&master->queue) || !master->running) {
 		if (!master->busy) {
 			spin_unlock_irqrestore(&master->queue_lock, flags);
@@ -916,11 +924,6 @@ static void spi_pump_messages(struct kth
 		return;
 	}
 
-	/* Make sure we are not already running a message */
-	if (master->cur_msg) {
-		spin_unlock_irqrestore(&master->queue_lock, flags);
-		return;
-	}
 	/* Extract head of queue */
 	master->cur_msg =
 		list_first_entry(&master->queue, struct spi_message, queue);