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![]() 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> |
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.. | ||
ashldi3.S | ||
ashrdi3.S | ||
backtrace.S | ||
bitops.h | ||
call_with_stack.S | ||
changebit.S | ||
clear_user.S | ||
clearbit.S | ||
copy_from_user.S | ||
copy_page.S | ||
copy_template.S | ||
copy_to_user.S | ||
csumipv6.S | ||
csumpartial.S | ||
csumpartialcopy.S | ||
csumpartialcopygeneric.S | ||
csumpartialcopyuser.S | ||
delay-loop.S | ||
delay.c | ||
div64.S | ||
ecard.S | ||
findbit.S | ||
floppydma.S | ||
getuser.S | ||
io-acorn.S | ||
io-readsb.S | ||
io-readsl.S | ||
io-readsw-armv3.S | ||
io-readsw-armv4.S | ||
io-writesb.S | ||
io-writesl.S | ||
io-writesw-armv3.S | ||
io-writesw-armv4.S | ||
lib1funcs.S | ||
lshrdi3.S | ||
Makefile | ||
memchr.S | ||
memcpy.S | ||
memmove.S | ||
memset.S | ||
memzero.S | ||
muldi3.S | ||
putuser.S | ||
setbit.S | ||
strchr.S | ||
strrchr.S | ||
testchangebit.S | ||
testclearbit.S | ||
testsetbit.S | ||
uaccess.S | ||
uaccess_with_memcpy.c | ||
ucmpdi2.S | ||
xor-neon.c |