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

[Anders Larsen]

Steven Scholz <steven.scholz at imc-berlin.de> schreibt:
>> this patch switches the at91rm9200 to synchronous clock mode after
>> initialization (it would otherwise stay in FastBus mode which is
>> the _slowest_ clock mode).
>
>But I thought FastBus mode is the prefered setting for ARM cpus.

Hi Steven,

FastBus is the default after reset but is not intended for normal
operation.

Quote from the ARM920T Technical Reference Manual (ARM DDI 0151C):
"On reset, the ARM920T is put into FastBus mode and operates using BCLK.
 A typical use for FastBus mode is to execute startup code while
 configuring a PLL under software control to produce FCLK at a higher
 frequency. When the PLL has stabilized and locked, you can switch the
 ARM920T to synchronous or asynchronous clocking using FCLK for normal
 operation."

Cheers
 Anders