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Commit 215e362d authored by Nicolas Pitre's avatar Nicolas Pitre Committed by Russell King
Browse files

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: default avatarNicolas Pitre <nico@linaro.org>
Signed-off-by: default avatarRussell King <rmk+kernel@arm.linux.org.uk>
parent 2374b063

arch/arm/include/asm/delay.h

+3 −3
Original line number Diff line number Diff line
@@ -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);

arch/arm/lib/Makefile

+4 −1
Original line number Diff line number Diff line
@@ -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

arch/arm/lib/delay-loop.S

+5 −10
Original line number Diff line number Diff line
@@ -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



/*