[U-Boot-Users] dynamic setting of CONFIG_SYS_CLK_FREQ

Wolfgang Denk wd at denx.de
Thu Apr 22 19:14:34 CEST 2004

In message <66FC73FC-9476-11D8-A48D-000393DBC2E8 at motorola.com> you wrote:
> I was wondering if there where an examples in the current u-boot source 
> tree in which CONFIG_SYS_CLK_FREQ was determined dynamically.  I have a 

Not exactly for CONFIG_SYS_CLK_FREQ - but the TQM8xxL boards  contain
code to measure the input clock against the (known) 32kHz clock.

> system in which I can read a config register on the board to let me 
> know if the CONFIG_SYS_CLK_FREQ is 66Mhz or 33Mhz.  I was hoping to 
> have the 16550 uart (and anything else) that needed CONFIG_SYS_CLK_FREQ 
> grab it from a variable instead.

If you provide a suitable init fuction which sets the  value  in  the
global  data  section eraly enough, you can probably shortcut the use

> This is on an MPC85xx platform system.

...or any other.

Best regards,

Wolfgang Denk

Software Engineering:  Embedded and Realtime Systems,  Embedded Linux
Phone: (+49)-8142-4596-87  Fax: (+49)-8142-4596-88  Email: wd at denx.de
"There are three principal ways to lose money: wine, women, and engi-
neers. While the first two are more pleasant, the third is by far the
more certain."                           - Baron Rothschild, ca. 1800

More information about the U-Boot mailing list