[U-Boot] OMAP3/devkit8000 division/multiplication function problems

[Graeme Russ <graeme.russ@gmail.com>]

Hi Simon,

On 14/06/11 18:52, Simon Schwarz wrote:
> Hi List,
> 
> as some may know I'am working on an SPL for the devkit8000.
> Now I have a problem with the UART init where I hope someone on the
> list can help.

Are you working with a latest version of U-Boot? Do you have additional
modifications not yet posted/committed?

> 
> My problem is in drivers/serial/serial.c with the function
> calc_divisor. With my defines this function is essentially just this:
> return (CONFIG_SYS_NS16550_CLK + (gd->baudrate * (MODE_X_DIV / 2))) /
> (MODE_X_DIV * gd->baudrate);
> 
> (Where MODE_X_DIV=16)
> 
> If i try to execute this line (with the step instruction of
> gdb/openOCD) the debugger just does not return and I have to use
> Strg+c to get a prompt.

Have you tried returning a hard-coded value?

> 
> Then the PC is 0x4020ffd4 (upper region of SRAM) and the CPSR is 0x600001d7
> 
> I think I have some problem with the division/multiplication functions
> as there is nothing else in this line which may cause trouble (returns
> and function calls worked before).

The problem may actually be related to gd access. I have had a heap (no pun
intended) of trouble getting gd access right in the past. Is this the first
access to gd?

> 
> U-boot is running in SRAM no SDRAM init yet.

If this is indeed the first access to gd, you need to look at the location
of gd in SRAM and make sure it not being clobbered

> 
> Has someone an idea where I can start looking? Maybe a known pitfall
> for beginners? More information needed?

Try adding another temporary variable to gd (ulong temp for example) and in
calc_divisor do:

	ulong temp = gd->temp;
	gd->temp = 1;

and step through

I'm sure that if I am wrong, somebody else here will be of further assistance

Regards,

Graeme