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

[Martin Krause]

Hi Anders,

u-boot-users-admin at lists.sourceforge.net wrote on :
> this patch switches the at91rm9200 to synchronous clock mode after
> initialization (it would otherwise stay in FastBus mode which is the
> _slowest_ clock mode). This lets the core run at full speed when not
> doing bus accesses, increasing overall performance by a factor of
> four. 
> 
> Changelog:
>   * patch by Anders Larsen, 2004-04-29
>     set the at91rm9200 clock to synchronous mode
> 
> Cheers
>  Anders

I've tested your patch on the cmc_pu2 board. Boot time is reduced
from about 32 s to 26 s with your patch (measured from starting power
supply to a specific status message of our linux application). This is
great! 

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?

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.

Regards,
Martin