[Gumstix-users] MMC Clock rate

[David F. <dav...@ya...>]

Craig,

This may show up as more of a problem for the
270.

For the PXA255:
It looks to me like the CLOCKRATE_MIN and
CLOCKRATE_MAX
in pxamci.h are wrong. P 3.3 of Developers Manual
indicates
a clock diagram where the max mmc clock is
19169280, this
would give a min clock rate of 299520.

The PXA27x:
CLOCKRATE_MIN = 304.688KHz CLOCKRATE_MAX=19.5MHZ
look ok.

If this is corrected (Russells) divisor
calculation will
fail.  I think a simpler approach would be to
calculate
the multiplier for the CLOCKRATE_MIN.  I believe
this
rounds in the safe direction.

       if (ios->clock) {
                unsigned int clk = ios->clock /
CLOCKRATE_MIN;
                host->clkrt = fls(clk);
Comments?

David.