From 6d4518d76f9612d580f9423cc0c3364a06b69588 Mon Sep 17 00:00:00 2001 From: Peter Teichmann Date: Mon, 20 Mar 2006 17:10:09 +0000 Subject: [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 --- arch/arm/lib/delay.S | 20 ++++++++++++-------- 1 file changed, 12 insertions(+), 8 deletions(-) (limited to 'arch/arm') diff --git a/arch/arm/lib/delay.S b/arch/arm/lib/delay.S index b3fb475b412..9183b06c0e2 100644 --- a/arch/arm/lib/delay.S +++ b/arch/arm/lib/delay.S @@ -9,28 +9,32 @@ */ #include #include +#include .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... */ -- cgit v1.2.3