2005-04-17 02:20:36 +04:00
|
|
|
/*
|
|
|
|
* linux/arch/arm/lib/delay.S
|
|
|
|
*
|
|
|
|
* Copyright (C) 1995, 1996 Russell King
|
|
|
|
*
|
|
|
|
* This program is free software; you can redistribute it and/or modify
|
|
|
|
* it under the terms of the GNU General Public License version 2 as
|
|
|
|
* published by the Free Software Foundation.
|
|
|
|
*/
|
|
|
|
#include <linux/linkage.h>
|
|
|
|
#include <asm/assembler.h>
|
2012-07-06 18:47:17 +04:00
|
|
|
#include <asm/delay.h>
|
2015-02-26 00:50:39 +03:00
|
|
|
|
2005-04-17 02:20:36 +04:00
|
|
|
.text
|
|
|
|
|
2005-11-12 00:51:49 +03:00
|
|
|
.LC0: .word loops_per_jiffy
|
2012-07-06 18:47:17 +04:00
|
|
|
.LC1: .word UDELAY_MULT
|
2005-04-17 02:20:36 +04:00
|
|
|
|
|
|
|
/*
|
2016-10-07 07:38:35 +03:00
|
|
|
* loops = r0 * HZ * loops_per_jiffy / 1000000
|
|
|
|
*
|
2006-03-20 20:10:09 +03:00
|
|
|
* r0 <= 2000
|
|
|
|
* HZ <= 1000
|
2005-04-17 02:20:36 +04:00
|
|
|
*/
|
2006-03-20 20:10:09 +03:00
|
|
|
|
2012-07-06 18:47:17 +04:00
|
|
|
ENTRY(__loop_udelay)
|
2006-03-20 20:10:09 +03:00
|
|
|
ldr r2, .LC1
|
2016-10-07 07:38:35 +03:00
|
|
|
mul r0, r2, r0 @ r0 = delay_us * UDELAY_MULT
|
|
|
|
ENTRY(__loop_const_udelay) @ 0 <= r0 <= 0xfffffaf0
|
2005-11-12 00:51:49 +03:00
|
|
|
ldr r2, .LC0
|
2015-02-26 00:50:39 +03:00
|
|
|
ldr r2, [r2]
|
2016-10-07 07:38:35 +03:00
|
|
|
umull r1, r0, r2, r0 @ r0-r1 = r0 * loops_per_jiffy
|
|
|
|
adds r1, r1, #0xffffffff @ rounding up ...
|
|
|
|
adcs r0, r0, r0 @ and right shift by 31
|
2014-06-30 19:29:12 +04:00
|
|
|
reteq lr
|
2005-04-17 02:20:36 +04:00
|
|
|
|
ARM: 7907/1: lib: delay-loop: Add align directive to fix BogoMIPS calculation
Currently mx53 (CortexA8) running at 1GHz reports:
Calibrating delay loop... 663.55 BogoMIPS (lpj=3317760)
Tom Evans verified that alignments of 0x0 and 0x8 run the two instructions of __loop_delay in one clock cycle (1 clock/loop), while alignments of 0x4 and 0xc take 3 clocks to run the loop twice. (1.5 clock/loop)
The original object code looks like this:
00000010 <__loop_const_udelay>:
10: e3e01000 mvn r1, #0
14: e51f201c ldr r2, [pc, #-28] ; 0 <__loop_udelay-0x8>
18: e5922000 ldr r2, [r2]
1c: e0800921 add r0, r0, r1, lsr #18
20: e1a00720 lsr r0, r0, #14
24: e0822b21 add r2, r2, r1, lsr #22
28: e1a02522 lsr r2, r2, #10
2c: e0000092 mul r0, r2, r0
30: e0800d21 add r0, r0, r1, lsr #26
34: e1b00320 lsrs r0, r0, #6
38: 01a0f00e moveq pc, lr
0000003c <__loop_delay>:
3c: e2500001 subs r0, r0, #1
40: 8afffffe bhi 3c <__loop_delay>
44: e1a0f00e mov pc, lr
After adding the 'align 3' directive to __loop_delay (align to 8 bytes):
00000010 <__loop_const_udelay>:
10: e3e01000 mvn r1, #0
14: e51f201c ldr r2, [pc, #-28] ; 0 <__loop_udelay-0x8>
18: e5922000 ldr r2, [r2]
1c: e0800921 add r0, r0, r1, lsr #18
20: e1a00720 lsr r0, r0, #14
24: e0822b21 add r2, r2, r1, lsr #22
28: e1a02522 lsr r2, r2, #10
2c: e0000092 mul r0, r2, r0
30: e0800d21 add r0, r0, r1, lsr #26
34: e1b00320 lsrs r0, r0, #6
38: 01a0f00e moveq pc, lr
3c: e320f000 nop {0}
00000040 <__loop_delay>:
40: e2500001 subs r0, r0, #1
44: 8afffffe bhi 40 <__loop_delay>
48: e1a0f00e mov pc, lr
4c: e320f000 nop {0}
, which now reports:
Calibrating delay loop... 996.14 BogoMIPS (lpj=4980736)
Some more test results:
On mx31 (ARM1136) running at 532 MHz, before the patch:
Calibrating delay loop... 351.43 BogoMIPS (lpj=1757184)
On mx31 (ARM1136) running at 532 MHz after the patch:
Calibrating delay loop... 528.79 BogoMIPS (lpj=2643968)
Also tested on mx6 (CortexA9) and on mx27 (ARM926), which shows the same
BogoMIPS value before and after this patch.
Reported-by: Tom Evans <tom_usenet@optusnet.com.au>
Suggested-by: Tom Evans <tom_usenet@optusnet.com.au>
Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
2013-11-30 18:24:42 +04:00
|
|
|
.align 3
|
2005-04-17 02:20:36 +04:00
|
|
|
|
|
|
|
@ Delay routine
|
2012-07-06 18:47:17 +04:00
|
|
|
ENTRY(__loop_delay)
|
2005-04-17 02:20:36 +04:00
|
|
|
subs r0, r0, #1
|
|
|
|
#if 0
|
2014-06-30 19:29:12 +04:00
|
|
|
retls lr
|
2005-04-17 02:20:36 +04:00
|
|
|
subs r0, r0, #1
|
2014-06-30 19:29:12 +04:00
|
|
|
retls lr
|
2005-04-17 02:20:36 +04:00
|
|
|
subs r0, r0, #1
|
2014-06-30 19:29:12 +04:00
|
|
|
retls lr
|
2005-04-17 02:20:36 +04:00
|
|
|
subs r0, r0, #1
|
2014-06-30 19:29:12 +04:00
|
|
|
retls lr
|
2005-04-17 02:20:36 +04:00
|
|
|
subs r0, r0, #1
|
2014-06-30 19:29:12 +04:00
|
|
|
retls lr
|
2005-04-17 02:20:36 +04:00
|
|
|
subs r0, r0, #1
|
2014-06-30 19:29:12 +04:00
|
|
|
retls lr
|
2005-04-17 02:20:36 +04:00
|
|
|
subs r0, r0, #1
|
2014-06-30 19:29:12 +04:00
|
|
|
retls lr
|
2005-04-17 02:20:36 +04:00
|
|
|
subs r0, r0, #1
|
|
|
|
#endif
|
2012-07-06 18:47:17 +04:00
|
|
|
bhi __loop_delay
|
2014-06-30 19:29:12 +04:00
|
|
|
ret lr
|
2012-07-06 18:47:17 +04:00
|
|
|
ENDPROC(__loop_udelay)
|
|
|
|
ENDPROC(__loop_const_udelay)
|
|
|
|
ENDPROC(__loop_delay)
|