On Tue, 2014-02-04 at 08:03 +0100, Holger Schurig wrote:
> Joe, look in linux/arch/arm/include/asm/delay.h. The macro udelay
> cannot handle large values because of lost-of-precision.
>
> IMHO udelay on ARM is broken, because it also cannot work with fast
> ARM processors (where bogomips >= 3355, which is in sight now). It's
> just not broken enought that someone did something against it ... so
> the current kludge is good enought.
Maybe something like this would be better?
---
arch/arm/include/asm/delay.h | 33 +++++++++++++++++++++++++++++----
1 file changed, 29 insertions(+), 4 deletions(-)
diff --git a/arch/arm/include/asm/delay.h b/arch/arm/include/asm/delay.h
index dff714d..ac33c56 100644
--- a/arch/arm/include/asm/delay.h
+++ b/arch/arm/include/asm/delay.h
@@ -15,6 +15,8 @@
#ifndef __ASSEMBLY__
+#include <linux/printk.h>
+
struct delay_timer {
unsigned long (*read_current_timer)(void);
unsigned long freq;
@@ -51,11 +53,34 @@ extern void __bad_udelay(void);
#define __udelay(n) arm_delay_ops.udelay(n)
#define __const_udelay(n) arm_delay_ops.const_udelay(n)
+#ifdef DEBUG
+#define __udelay_debug_max_delay(n) \
+do { \
+ if (n > MAX_UDELAY_MS * 1000) { \
+ pr_debug("udelay(%d) too large - Convert to mdelay\n", n); \
+ dump_stack(); \
+ } \
+} while (0)
+#else
+#define __udelay_debug_max_delay(n) \
+ do {} while (0)
+#endif
+
#define udelay(n) \
- (__builtin_constant_p(n) ? \
- ((n) > (MAX_UDELAY_MS * 1000) ? __bad_udelay() : \
- __const_udelay((n) * UDELAY_MULT)) : \
- __udelay(n))
+({ \
+ if (__builtin_constant_p(n)) { \
+ typeof n _n = n; \
+ while (_n > MAX_UDELAY_MS * 1000) { \
+ __const_udelay(MAX_UDELAY_MS * 1000 * UDELAY_MULT); \
+ _n -= MAX_UDELAY_MS * 1000; \
+ } \
+ if (_n) \
+ __const_udelay(_n * 1000 * UDELAY_MULT); \
+ } else { \
+ __udelay_debug_max_delay(n); \
+ __udelay(n); \
+ } \
+})
/* Loop-based definitions for assembly code. */
extern void __loop_delay(unsigned long loops);
--
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