[U-Boot-Users] Question about setting the sys clk freq based on a pull up on io.

Andrew May acmay at acmay.homeip.net
Wed Nov 19 03:22:35 CET 2003

On Tue, Nov 18, 2003 at 06:02:29PM -0800, Conn Clark wrote:
> Hello all,
> 	Our design is based on a 333MHz IBM405EP processor. We wish to 
> 	detect the oscilator speed we are using via a pullup or pulldown resistor 
> on an IO line. In order to make our product cheap we were planning to drive 
> 	My problem is how do I go about this without severly modifying 
> 	U-Boots structure. In analyzing how to do this I determined that the 
> configuration and reading of the IO pin sould be done in a 
> board_pre_init function. This rases the issue of passing values between 
> the init functions called by board_init_f. My second issue is how do I 
> deal with the two frquencies since only one can be defined as 
> CONFIG_SYS_CLK_FREQ(which is used in several places) without sticking 
> lots of nasty board specific ifdefs through out the code.
I just have an old copy of the code to look at but for the 405 stuff
_SYS_CLK_FREQ is only used in C code so you can do this in the header
and c code.

#define CONFIG_SYS_CLK_FREQ get_sys_clk_freq()

unsigned int get_sys_clk_freq()
	if( *ADDR == 0x1 )
		return 25000000;
		return 33333333;

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