[PATCH] AVM C4 ISDN card : use cpu_relax() in busy loops

[Willy Tarreau]

As suggested by Alan, use cpu_relax() in 3 busy loops : "It's a
polled busy loop so you want other CPU threads to run if possible".

Signed-off-by: Willy Tarreau <w@xxxxxx>
---
 drivers/isdn/hardware/avm/c4.c |    7 ++++---
 1 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/isdn/hardware/avm/c4.c b/drivers/isdn/hardware/avm/c4.c
index f7253b2..8149dce 100644
--- a/drivers/isdn/hardware/avm/c4.c
+++ b/drivers/isdn/hardware/avm/c4.c
@@ -22,6 +22,7 @@ #include <linux/capi.h>
 #include <linux/kernelcapi.h>
 #include <linux/init.h>
 #include <asm/io.h>
+#include <asm/processor.h>
 #include <asm/uaccess.h>
 #include <linux/netdevice.h>
 #include <linux/isdn/capicmd.h>
@@ -149,7 +150,7 @@ static inline int wait_for_doorbell(avmc
 	while (c4inmeml(card->mbase+DOORBELL) != 0xffffffff) {
 		if (!time_before(jiffies, stop))
 			return -1;
-		mb();
+		cpu_relax();
 	}
 	return 0;
 }
@@ -302,7 +303,7 @@ static void c4_reset(avmcard *card)
 		if (!time_before(jiffies, stop))
 			return;
 		c4outmeml(card->mbase+DOORBELL, DBELL_ADDR);
-		mb();
+		cpu_relax();
 	}
 
 	c4_poke(card, DC21285_ARMCSR_BASE + CHAN_1_CONTROL, 0);
@@ -326,7 +327,7 @@ static int c4_detect(avmcard *card)
 		if (!time_before(jiffies, stop))
 			return 2;
 		c4outmeml(card->mbase+DOORBELL, DBELL_ADDR);
-		mb();
+		cpu_relax();
 	}
 
 	c4_poke(card, DC21285_ARMCSR_BASE + CHAN_1_CONTROL, 0);
-- 
1.4.1

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