[U-Boot] [PATCH-OMAP3] OMAP3: Fix typo and cp_delay

[U-Boot] [PATCH-OMAP3] OMAP3: Fix typo and cp_delay

[dirk.behme at googlemail.com]

Subject: [PATCH-OMAP3] OMAP3: Fix typo and cp_delay

From: Dirk Behme <dirk.behme@gmail.com>

Fix typo and cp_delay. Requested by Wolfgang Denk.

Signed-off-by: Dirk Behme <dirk.behme@gmail.com>

---

Regarding cp_delay there was the comment:

-- cut --
>+static void cp_delay(void)
>+{
>+	volatile int i;
>+
>+	/* Many OMAP regs need at least 2 nops */
>+	for (i = 0; i < 100; i++) ;

There is not much reason for the compiler not to optimize this code away.
-- cut --

Please note that most of ARM code uses *this* cp_delay() implementation. If I understood correctly at IRC, Scott Wood made some tests and volatile prevents gcc from optimizing loop away.

 cpu/arm_cortexa8/cpu.c   |    5 ++---
 cpu/arm_cortexa8/start.S |    2 +-
 2 files changed, 3 insertions(+), 4 deletions(-)

Index: u-boot-arm/cpu/arm_cortexa8/start.S
===================================================================
--- u-boot-arm.orig/cpu/arm_cortexa8/start.S
+++ u-boot-arm/cpu/arm_cortexa8/start.S
@@ -394,7 +394,7 @@ irq:
 	.align	5
 fiq:
 	get_fiq_stack
-	/* someone ought to write a more effiction fiq_save_user_regs */
+	/* someone ought to write a more effective fiq_save_user_regs */
 	irq_save_user_regs
 	bl	do_fiq
 	irq_restore_user_regs
Index: u-boot-arm/cpu/arm_cortexa8/cpu.c
===================================================================
--- u-boot-arm.orig/cpu/arm_cortexa8/cpu.c
+++ u-boot-arm/cpu/arm_cortexa8/cpu.c
@@ -68,10 +68,9 @@ static void write_p15_c1(unsigned long v
 
 static void cp_delay(void)
 {
-	volatile int i;
-
 	/* Many OMAP regs need@least 2 nops */
-	for (i = 0; i < 100; i++) ;
+	asm("nop");
+	asm("nop");
 }
 
 /* See also ARM Ref. Man. */

[U-Boot] [PATCH-OMAP3] OMAP3: Fix typo and cp_delay

[Wolfgang Denk]

Dear dirk.behme at googlemail.com,

In message <49172e21.0407560a.71cf.ffffba13@mx.google.com> you wrote:
> Subject: [PATCH-OMAP3] OMAP3: Fix typo and cp_delay
> 
> From: Dirk Behme <dirk.behme@gmail.com>
> 
> Fix typo and cp_delay. Requested by Wolfgang Denk.

See previous comments.

> Signed-off-by: Dirk Behme <dirk.behme@gmail.com>
> 
> ---
> 
> Regarding cp_delay there was the comment:
> 
> -- cut --
> >+static void cp_delay(void)
> >+{
> >+	volatile int i;
> >+
> >+	/* Many OMAP regs need at least 2 nops */
> >+	for (i = 0; i < 100; i++) ;
> 
> There is not much reason for the compiler not to optimize this code away.
> -- cut --
> 
> Please note that most of ARM code uses *this* cp_delay() implementation. If I understood correctly at IRC, Scott Wood made some tests and volatile prevents gcc from optimizing loop away.

Now this is actually some interesting information which probably
should be part of the commit message - in the present form, it just
gets lost.

Best regards,

Wolfgang Denk

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