8xx i2c refers to unspecified chip errata

[Joakim Tjernlund]

As-is for me. No problems reported to me.

         Joakim

> Tom + Joakim,
> we're doing a release soon over here at sensors/i2c,
> do you want this checked in as-is, with mods, or not at all?
>
> Joakim Tjernlund wrote:
> >
> > > >
> > > > Here is a patch against the PPC 2.4 devel tree for the i2c-algo-8xx.c
> > >
> > > Can you please split this into logical chunks, or give me a list of each
> > > fix in here?  Thanks.
> >
> > ohh, kind of hard to remember all that went into that patch. The path
> > has evoled over many days, but I can try summarize. I have tested this code
> > pretty well it does not fail for me. Speed has been between 10-150KHz. The
> > old code fails as soon you start to stress it a little.
> >
> >  - replace invalidate_dcache_range with flush_dcache_range, since buffers are
> >    NOT cache aligned. flush will write to memory AND invalidate the cache.
> >
> >  - move the chip errata stuff from irq routine into read/write routines. Made
> >    it default off since it causes lock ups on my I2C device. I think it causes
> >    a too short STOP condition. If enabled I2C will behave better than before, but
> >    may still cause problems if the read/write is interrupted with a signal while
> >    microcode is enabled.
> >
> >  - set default speed to 60 KHz instead.
> >
> >  - missing/faulty initialization of parameter ram when I2C micro patch is active.
> >
> >  - replaced assingments with mask operations with relevant bits. Example:
> >       /* Shut down IIC. */
> >       i2c->i2c_i2mod = 0;
> >         i2c->i2c_i2mod &= ~1;
> >
> >  - When reading from I2C device, let the receive BD generate interrupt instead of
> >    the dummy trasmit. This is important since the TX interrupt will be too early sometimes, before
> >    the RX BD has closed. There is one case where the RX irq is before the TX irq, if iic_mrblr is set
> >    to match the number of bytes to read. Therefore must the iic_mrblr be one byte larger than
> >    the expected number of bytes.
> >
> >  - busy wait for small transfers since it's faster.
> >
> >  - save_flags(flags); cli(); cleanups
> >
> >  - interruptible_sleep_on_timeout() instead of interruptible_sleep_on() so it won't hang forever if an
> >    irq is lost.
> >
> >  Jocke

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