[PATCH] IXP425: Fixing timer code
The non-interrupted timer code is inaccurate.
I found that the timing error of udelay() is caused by
to much looping overhead. The actual timing routine
was called repeatedly for each microsecond. When
I used bigger slices it became more accurate.
Some IXP425 ports have this line in their config file:
#define CONFIG_SYS_HZ 3333333 /* spec says 66.666 MHz,
but it appears to be 33 */
With this patch, this is nonsense. Instead you should use:
#ifdef CONFIG_USE_IRQ
/* Interrupt driven timer wants system tick here */
#define CONFIG_SYS_HZ 1000
#else
/* The code in cpu/ixp/timer.c needs timer clock tick in HZ */
#define CONFIG_SYS_HZ 66666666
#endif
The patch is against "latest" u-boot git-repository
Please (still) be patient if style of submission or patches are
offending.
Signed-off-by: Stefan Althoefer <[EMAIL PROTECTED]>
----
diff -uprN u-boot-orig//cpu/ixp/timer.c u-boot/cpu/ixp/timer.c
--- u-boot-orig//cpu/ixp/timer.c 2008-12-02 17:25:31.000000000 +0100
+++ u-boot/cpu/ixp/timer.c 2008-12-02 22:27:22.000000000 +0100
@@ -46,6 +46,8 @@ void ixp425_udelay(unsigned long usec)
*/
unsigned long usecs = CONFIG_SYS_HZ/1000000L & ~IXP425_OST_RELOAD_MASK;
+ usecs *= usec;
+
*IXP425_OSST = IXP425_OSST_TIMER_1_PEND;
usecs |= IXP425_OST_ONE_SHOT | IXP425_OST_ENABLE;
*IXP425_OSRT1 = usecs;
@@ -54,7 +56,13 @@ void ixp425_udelay(unsigned long usec)
void udelay (unsigned long usec)
{
- while (usec--) ixp425_udelay(1);
+ /* ipx425_udelay has big overhead, so call it in bigger slices */
+ while (usec>1000){
+ ixp425_udelay(1000);
+ usec -= 1000;
+ }
+ /* and now the rest */
+ ixp425_udelay(usec);
}
static ulong reload_constant = 0xfffffff0;
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