[PATCH] cpu_relax whilst in busy-wait loops.

drivers/char/drm/gamma_dma.c

@@ -44,9 +44,14 @@ static inline void gamma_dma_dispatch(drm_device_t *dev, unsigned long address,
 	drm_gamma_private_t *dev_priv =
 				(drm_gamma_private_t *)dev->dev_private;
 	mb();
-	while ( GAMMA_READ(GAMMA_INFIFOSPACE) < 2);
+	while ( GAMMA_READ(GAMMA_INFIFOSPACE) < 2)
+		cpu_relax();
+
 	GAMMA_WRITE(GAMMA_DMAADDRESS, address);
-	while (GAMMA_READ(GAMMA_GCOMMANDSTATUS) != 4);
+
+	while (GAMMA_READ(GAMMA_GCOMMANDSTATUS) != 4)
+		cpu_relax();
+
 	GAMMA_WRITE(GAMMA_DMACOUNT, length / 4);
 }
 
@@ -54,16 +59,18 @@ void gamma_dma_quiescent_single(drm_device_t *dev)
 {
 	drm_gamma_private_t *dev_priv =
 				(drm_gamma_private_t *)dev->dev_private;
-	while (GAMMA_READ(GAMMA_DMACOUNT));
+	while (GAMMA_READ(GAMMA_DMACOUNT))
+		cpu_relax();
 
-	while (GAMMA_READ(GAMMA_INFIFOSPACE) < 2);
+	while (GAMMA_READ(GAMMA_INFIFOSPACE) < 2)
+		cpu_relax();
 
 	GAMMA_WRITE(GAMMA_FILTERMODE, 1 << 10);
 	GAMMA_WRITE(GAMMA_SYNC, 0);
 
 	do {
 		while (!GAMMA_READ(GAMMA_OUTFIFOWORDS))
-			;
+			cpu_relax();
 	} while (GAMMA_READ(GAMMA_OUTPUTFIFO) != GAMMA_SYNC_TAG);
 }
 
@@ -71,9 +78,11 @@ void gamma_dma_quiescent_dual(drm_device_t *dev)
 {
 	drm_gamma_private_t *dev_priv =
 				(drm_gamma_private_t *)dev->dev_private;
-	while (GAMMA_READ(GAMMA_DMACOUNT));
+	while (GAMMA_READ(GAMMA_DMACOUNT))
+		cpu_relax();
 
-	while (GAMMA_READ(GAMMA_INFIFOSPACE) < 3);
+	while (GAMMA_READ(GAMMA_INFIFOSPACE) < 3)
+		cpu_relax();
 
 	GAMMA_WRITE(GAMMA_BROADCASTMASK, 3);
 	GAMMA_WRITE(GAMMA_FILTERMODE, 1 << 10);
@@ -81,12 +90,14 @@ void gamma_dma_quiescent_dual(drm_device_t *dev)
 
 	/* Read from first MX */
 	do {
-		while (!GAMMA_READ(GAMMA_OUTFIFOWORDS));
+		while (!GAMMA_READ(GAMMA_OUTFIFOWORDS))
+			cpu_relax();
 	} while (GAMMA_READ(GAMMA_OUTPUTFIFO) != GAMMA_SYNC_TAG);
 
 	/* Read from second MX */
 	do {
-		while (!GAMMA_READ(GAMMA_OUTFIFOWORDS + 0x10000));
+		while (!GAMMA_READ(GAMMA_OUTFIFOWORDS + 0x10000))
+			cpu_relax();
 	} while (GAMMA_READ(GAMMA_OUTPUTFIFO + 0x10000) != GAMMA_SYNC_TAG);
 }
 
@@ -94,14 +105,15 @@ void gamma_dma_ready(drm_device_t *dev)
 {
 	drm_gamma_private_t *dev_priv =
 				(drm_gamma_private_t *)dev->dev_private;
-	while (GAMMA_READ(GAMMA_DMACOUNT));
+	while (GAMMA_READ(GAMMA_DMACOUNT))
+		cpu_relax();
 }
 
 static inline int gamma_dma_is_ready(drm_device_t *dev)
 {
 	drm_gamma_private_t *dev_priv =
 				(drm_gamma_private_t *)dev->dev_private;
-	return(!GAMMA_READ(GAMMA_DMACOUNT));
+	return (!GAMMA_READ(GAMMA_DMACOUNT));
 }
 
 irqreturn_t gamma_dma_service(int irq, void *device, struct pt_regs *regs)
@@ -113,7 +125,9 @@ irqreturn_t gamma_dma_service(int irq, void *device, struct pt_regs *regs)
 
 	atomic_inc(&dev->counts[6]); /* _DRM_STAT_IRQ */
 
-	while (GAMMA_READ(GAMMA_INFIFOSPACE) < 3);
+	while (GAMMA_READ(GAMMA_INFIFOSPACE) < 3)
+		cpu_relax();
+
 	GAMMA_WRITE(GAMMA_GDELAYTIMER, 0xc350/2); /* 0x05S */
 	GAMMA_WRITE(GAMMA_GCOMMANDINTFLAGS, 8);
 	GAMMA_WRITE(GAMMA_GINTFLAGS, 0x2001);
@@ -824,7 +838,8 @@ void DRM(driver_irq_preinstall)( drm_device_t *dev ) {
 	drm_gamma_private_t *dev_priv =
 				(drm_gamma_private_t *)dev->dev_private;
 
-	while(GAMMA_READ(GAMMA_INFIFOSPACE) < 2);
+	while(GAMMA_READ(GAMMA_INFIFOSPACE) < 2)
+		cpu_relax();
 
 	GAMMA_WRITE( GAMMA_GCOMMANDMODE,	0x00000004 );
 	GAMMA_WRITE( GAMMA_GDMACONTROL,		0x00000000 );
@@ -834,7 +849,8 @@ void DRM(driver_irq_postinstall)( drm_device_t *dev ) {
 	drm_gamma_private_t *dev_priv =
 				(drm_gamma_private_t *)dev->dev_private;
 
-	while(GAMMA_READ(GAMMA_INFIFOSPACE) < 3);
+	while(GAMMA_READ(GAMMA_INFIFOSPACE) < 3)
+		cpu_relax();
 
 	GAMMA_WRITE( GAMMA_GINTENABLE,		0x00002001 );
 	GAMMA_WRITE( GAMMA_COMMANDINTENABLE,	0x00000008 );
@@ -847,7 +863,8 @@ void DRM(driver_irq_uninstall)( drm_device_t *dev ) {
 	if (!dev_priv)
 		return;
 
-	while(GAMMA_READ(GAMMA_INFIFOSPACE) < 3);
+	while(GAMMA_READ(GAMMA_INFIFOSPACE) < 3)
+		cpu_relax();
 
 	GAMMA_WRITE( GAMMA_GDELAYTIMER,		0x00000000 );
 	GAMMA_WRITE( GAMMA_COMMANDINTENABLE,	0x00000000 );