8xx i2c refers to unspecified chip errata

Joakim Tjernlund joakim.tjernlund at lumentis.se
Thu Oct 24 20:21:50 CEST 2002

> > 
> > 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.


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