[U-Boot-Users] bd->bi_opbfreq initialization lib_ppc/board.c

[listmember at orkun.us]

The following is the code fragment from lib_ppc/board.c.

%%% begin fragment %%%

#if defined(CONFIG_405GP) || defined(CONFIG_405EP)
        bd->bi_pci_busfreq = get_PCI_freq ();

#ifdef CFG_OPB_FREQ
        bd->bi_opbfreq = CFG_OPB_FREQ;
#else
        bd->bi_opbfreq = 50000000;
#endif
        bd->bi_iic_fast[0] = 0;
        bd->bi_iic_fast[1] = 0;
#endif
#endif

%%% end fragment %%%

Why is bi_opbfreq not initialized as:

        bd->bi_opbfreq = get_OPB_freq();

get_OPB_freq() returns the actual OPB frequency based on PLB freq and
PLB:OPB divisor (based on pllmr &  strap read only registers in PPC405).

This value is not used by u-boot but Linux uses it in I2C divisor
initialization (linux/drivers/i2c/i2c-ibm_iic.c). On Cogent  CSB272 board
the OPB freq is set to 16.67Mhz so the effective I2C clock was much lower
because wrong value was communicated to Linux.

I patched my version of board.c to use get_OPB_freq() in the else case
(replaced constant 50000000 with get_OPB_freq() call) and it worked well.
I personally do not see why CFG_OPB_FREQ is needed at all (only one board
is using it and set to 50Mhz). If nobody objects, I would like to send a
patch for it.

2 choice for the patch:

1) I can send a patch so CFG_OPB_FREQ is removed and bi_opbfreq is always
initialied to correct value via get_OPB_freq().

2) I can keep CFG_OPB_FREQ override (for that one board) and change the
default in else case to get_OPB_freq().

Which one would you favor?

Regards,
Tolunay