AW: [U-Boot-Users] [PATCH 4/4] add csb637 (at91rm9200) support

[Anders Larsen]

"Martin Krause" <Martin.Krause at tqs.de> schreibt:
>I wonder if there are some pitfalls doing this on the AT91RM9200 cpu? 
>As I understand the ARM920T Technical Reference Manual the clocking 
>modes are a feature of the ARM920T core and not affected by the 
>surrounding on-chip peripherals added by Atmel. So it should work for 
>all cpu's with ARM920T core without problems?

Hi Martin,

there might be some boards with ARM920T cpu who can't use synchronous
clock mode due to clock restrictions (see the TRM), but I really
can't tell.
>
>I've also done an nbench benchmark under linux running in synchronous
>clock mode. But the results are the same as in fast bus clock mode. 
>Strange. I've no idea why.

Perhaps your Linux switches clock mode itself? (the at91rm9200 patch
from maxim.org.za does _not_, however)
What does /proc/cpuinfo say about this?
With my patch I get:
# grep -i bogomips /proc/cpuinfo
BogoMIPS        : 91.95
and without it I get appr. 28.
I get the same speed improvement (x4) using an RSA encryption benchmark.

For reference here's the output from nbench 2.2.2 on my csb637 board:
BYTEmark* Native Mode Benchmark ver. 2 (10/95)
Index-split by Andrew D. Balsa (11/97)
Linux/Unix* port by Uwe F. Mayer (12/96,11/97)

TEST                : Iterations/sec.  : Old Index   : New Index
                    :                  : Pentium 90* : AMD K6/233*
--------------------:------------------:-------------:------------
NUMERIC SORT        :          56.635  :       1.45  :       0.48
STRING SORT         :          3.5857  :       1.60  :       0.25
BITFIELD            :      1.2262e+07  :       2.10  :       0.44
FP EMULATION        :          5.5644  :       2.67  :       0.62
FOURIER             :          6.0343  :       0.01  :       0.00
ASSIGNMENT          :         0.43937  :       1.67  :       0.43
IDEA                :          186.71  :       2.86  :       0.85
HUFFMAN             :          22.129  :       0.61  :       0.20
NEURAL NET          :       0.0072986  :       0.01  :       0.00
LU DECOMPOSITION    :          0.2586  :       0.01  :       0.01
==========================ORIGINAL BYTEMARK RESULTS======================
INTEGER INDEX       : 1.683
FLOATING-POINT INDEX: 0.010
Baseline (MSDOS*)   : Pentium* 90, 256 KB L2-cache, Watcom* compiler 10.0
==============================LINUX DATA BELOW===========================
CPU                 : 
L2 Cache            : 
OS                  : Linux 2.6.12-rc1-csb
C compiler          : arm_v4le-gcc
libc                : static
MEMORY INDEX        : 0.362
INTEGER INDEX       : 0.470
FLOATING-POINT INDEX: 0.006
Baseline (LINUX)    : AMD K6/233*, 512 KB L2-cache, gcc 2.7.2.3,
libc-5.4.38
* Trademarks are property of their respective holder.

Cheers
 Anders