[PATCH] cpu_relax whilst in busy-wait loops.

diff --git a/drivers/char/drm/gamma_dma.c b/drivers/char/drm/gamma_dma.c
index 9608c37a1b772481b7ab9880d34b019c17d338cd..9a8eba82b9dc0c90486107ef854ed7c97369a219 100644 (file)
--- a/drivers/char/drm/gamma_dma.c
+++ b/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 );