ENGR00133737 MXC SDMA: fix system hangs when play audio with irq threaded

When apply rt patch or turn on hardirq threaded in kernel,
play audio by application with realtime schedule policy hangs the system.

It is caused by:
Requesting SDMA channel, a specific channel is used to load script
and context from memory.

This load phase also uses sdma to transfer, then poll
a complete flag within a while(1) loop.

When application with realtime schedule policy request sdma channel,
it will preempt threaded irqs and prevent complete flag to be set.

So a deadlock appears.

Signed-off-by: Zeng Zhaoming <b32542@freescale.com>

1 files changed, 8 insertions, 2 deletions

diff --git a/arch/arm/plat-mxc/sdma/iapi/src/iapiLow.c b/arch/arm/plat-mxc/sdma/iapi/src/iapiLow.c
index 92d3fa4ebf6e..47611fe52743 100644
--- a/arch/arm/plat-mxc/sdma/iapi/src/iapiLow.c
+++ b/arch/arm/plat-mxc/sdma/iapi/src/iapiLow.c
@@ -33,6 +33,8 @@
 /* ****************************************************************************
  * Include File Section
  *****************************************************************************/
+#include <linux/preempt.h>
+#include <linux/hardirq.h>
 #include "epm.h"
 #include "iapiLow.h"
 
@@ -118,8 +120,12 @@ iapi_ChangeCallbackISR(channelDescriptor *cd_p,
  */
 void iapi_lowSynchChannel(unsigned char channel)
 {
-	while (!((1UL << channel) & iapi_SDMAIntr))
-		;
+	if (preempt_count() || in_interrupt()) {
+		 while (!((1UL << channel) & iapi_SDMAIntr))
+			 ;
+	} else
+		GOTO_SLEEP(channel);
+
 	iapi_SDMAIntr &= ~(1UL << channel);
 }