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ARM: 8306/1: loop_udelay: remove bogomips value limitation 

Now that we don't support ARMv3 anymore, the loop based delay code can
convert microsecs into number of loops using a 64-bit multiplication
and more precision.

This allows us to lift the hard limit of 3355 on the bogomips value as
loops_per_jiffy may now safely span the full 32-bit range.

Signed-off-by: Nicolas Pitre <nico@linaro.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
This commit is contained in:
Nicolas Pitre 2015-02-25 22:50:39 +01:00 committed by Russell King
parent 2374b063c3
commit 215e362daf
3 changed files with 12 additions and 14 deletions
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6
arch/arm/include/asm/delay.h
View File

@ -10,8 +10,8 @@
#include <asm/param.h> /* HZ */
#define MAX_UDELAY_MS 2
#define UDELAY_MULT ((UL(2199023) * HZ) >> 11)
#define UDELAY_SHIFT 30
#define UDELAY_MULT UL(2047 * HZ + 483648 * HZ / 1000000)
#define UDELAY_SHIFT 31
#ifndef __ASSEMBLY__
@ -34,7 +34,7 @@ extern struct arm_delay_ops {
* it, it means that you're calling udelay() with an out of range value.
*
* With currently imposed limits, this means that we support a max delay
* of 2000us. Further limits: HZ<=1000 and bogomips<=3355
* of 2000us. Further limits: HZ<=1000
*/
extern void __bad_udelay(void);

5
arch/arm/lib/Makefile
View File

@ -29,7 +29,10 @@ else
lib-y += io-readsw-armv4.o io-writesw-armv4.o
endif
lib-$(CONFIG_ARCH_RPC) += ecard.o io-acorn.o floppydma.o
ifeq ($(CONFIG_ARCH_RPC),y)
lib-y += ecard.o io-acorn.o floppydma.o
AFLAGS_delay-loop.o += -march=armv4
endif
$(obj)/csumpartialcopy.o: $(obj)/csumpartialcopygeneric.S
$(obj)/csumpartialcopyuser.o: $(obj)/csumpartialcopygeneric.S

15
arch/arm/lib/delay-loop.S
View File

@ -10,6 +10,7 @@
#include <linux/linkage.h>
#include <asm/assembler.h>
#include <asm/delay.h>
.text
.LC0: .word loops_per_jiffy
@ -17,7 +18,6 @@
/*
* r0 <= 2000
* lpj <= 0x01ffffff (max. 3355 bogomips)
* HZ <= 1000
*/
@ -25,16 +25,11 @@ ENTRY(__loop_udelay)
ldr r2, .LC1
mul r0, r2, r0
ENTRY(__loop_const_udelay) @ 0 <= r0 <= 0x7fffff06
mov r1, #-1
ldr r2, .LC0
ldr r2, [r2] @ max = 0x01ffffff
add r0, r0, r1, lsr #32-14
mov r0, r0, lsr #14 @ max = 0x0001ffff
add r2, r2, r1, lsr #32-10
mov r2, r2, lsr #10 @ max = 0x00007fff
mul r0, r2, r0 @ max = 2^32-1
add r0, r0, r1, lsr #32-6
movs r0, r0, lsr #6
ldr r2, [r2]
umull r1, r0, r2, r0
adds r1, r1, #0xffffffff
adcs r0, r0, r0
reteq lr
/*