Hi,

On 19 September 2016 at 21:50, dh@synoia.com wrote:

I modified the current u-boot code to store r2 in rpi.c board_init, but only get a zero value from the register.

It could be one of three issues:

1. My use of the c asm statement to store r2 is wrong (I've never done this before), assembler yes, c assembler no.
2. The compiler has consumed the value of r2 before getting to board_init
3. The pi firmware does not put the fdt value in r2.

asm statement to store r2 is asm("mov %%r2, %0" : "=r" (gd->bd->bpi_boot_parms) );

In order to use up Marco's ATAG and FDT code.

What the earliest place where I can store the input r2 value?

You could try save_boot_params(). Some boards use that. But gd is not available then - perhaps you could put it in a variable in the data segment?

Hopefully, I'm putting the r2 value into gd->bd->bpi_boot_parms in board_init, but it appear it is zero at that point.

Should I restrict the compiler's use of r2? (I'm reluctant to limit the compiler in that manner)?

Suggestion would be welcome.

Thanks Duncan Hare

714 931 7952

Regards, Simon

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