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| author | Peter Teichmann <mail@peter-teichmann.de> | 2006-03-20 18:10:09 +0100 |
|---|---|---|
| committer | Russell King <rmk+kernel@arm.linux.org.uk> | 2006-03-21 23:06:07 +0100 |
| commit | 6d4518d76f9612d580f9423cc0c3364a06b69588 (patch) | |
| tree | 27e2287ecc9b858089a667def26b7d9555212337 /arch/arm/lib/delay.S | |
| parent | [ARM] 3334/1: Add support for IXDP28x5 platforms (diff) | |
| download | linux-6d4518d76f9612d580f9423cc0c3364a06b69588.tar.xz linux-6d4518d76f9612d580f9423cc0c3364a06b69588.zip | |
[ARM] 3346/1: Fix udelay() for HZ values different from 100
Patch from Peter Teichmann
Currently, if the kernels HZ value is greater than 100, delays with the udelay function are too short. This can cause trouble for instance with the zd1201 usb wlan driver.
This patch suggests a solution that keeps the overhead small and maintains (hopefully) sufficient resolution.
Signed-off-by: Peter Teichmann
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Diffstat (limited to 'arch/arm/lib/delay.S')
| -rw-r--r-- | arch/arm/lib/delay.S | 20 |
1 files changed, 12 insertions, 8 deletions
diff --git a/arch/arm/lib/delay.S b/arch/arm/lib/delay.S index b3fb475b4120..9183b06c0e2f 100644 --- a/arch/arm/lib/delay.S +++ b/arch/arm/lib/delay.S @@ -9,28 +9,32 @@ */ #include <linux/linkage.h> #include <asm/assembler.h> +#include <asm/param.h> .text .LC0: .word loops_per_jiffy +.LC1: .word (2199023*HZ)>>11 /* - * 0 <= r0 <= 2000 + * r0 <= 2000 + * lpj <= 0x01ffffff (max. 3355 bogomips) + * HZ <= 1000 */ + ENTRY(__udelay) - mov r2, #0x6800 - orr r2, r2, #0x00db + ldr r2, .LC1 mul r0, r2, r0 -ENTRY(__const_udelay) @ 0 <= r0 <= 0x01ffffff +ENTRY(__const_udelay) @ 0 <= r0 <= 0x7fffff06 ldr r2, .LC0 - ldr r2, [r2] @ max = 0x0fffffff - mov r0, r0, lsr #11 @ max = 0x00003fff - mov r2, r2, lsr #11 @ max = 0x0003ffff + ldr r2, [r2] @ max = 0x01ffffff + mov r0, r0, lsr #14 @ max = 0x0001ffff + mov r2, r2, lsr #10 @ max = 0x00007fff mul r0, r2, r0 @ max = 2^32-1 movs r0, r0, lsr #6 RETINSTR(moveq,pc,lr) /* - * loops = (r0 * 0x10c6 * 100 * loops_per_jiffy) / 2^32 + * loops = r0 * HZ * loops_per_jiffy / 1000000 * * Oh, if only we had a cycle counter... */ |