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    SubjectRe: [PATCH 2/3] Add GD-Rom support to the SEGA Dreamcast

    On Sun, 2007-12-16 at 18:50 +0900, Paul Mundt wrote:
    > Ok, I don't know anything about the CD-ROM layer, so I've just commented
    > on the general and SH-specific stuff. Hopefully someone with a clue
    > in this area (ie, not me) can offer input on the rest of the bits.

    > > +static char gdrom_execute_diagnostic(void)
    > > +{
    > > + int count;
    > > + /* Restart the GDROM */
    > > + ctrl_outl(0x1fffff, GDROM_RESET_REG);
    > > + for (count = 0xa0000000; count < 0xa0200000; count += 4)
    > > + ctrl_inl(count);
    > Er? This ranged dummy reading of the P2 space needs some explanation. The
    > GD-ROM isn't even mapped in to this space, so this seems like a hack to
    > either work around a timing issue or a write ordering problem.

    I'll confess to not knowing what it's up to here either, other than it
    looks like a mechanism to cause a G1 bus reset. This is a progressive
    read of the Boot ROM area and that is all under G1 control (as is the GD
    Rom obviously)

    Replacing it with a simple delay of any length or, say, a read of one
    word and then a delay, doesn't work.

     \ /
      Last update: 2007-12-16 18:35    [W:0.021 / U:4.740 seconds]
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