[U-Boot-Users] Heads up for ppl using the cpu/mpc8xx/spi.c

Wolfgang Denk wd at denx.de
Mon Jul 26 23:46:17 CEST 2004

In message <OF860C514F.59EEA3B3-ON85256EDD.005E8AF9-85256EDD.005F7807 at nanometrics.ca> you wrote:
> > Question 1: why are you using this old version?
> I would love to go with a newer version but after patching in my changes to
> 1.0.2 u-boot doesn't boot, so I'm left with a business decision that

Well, U-Boot 1.0.2 is out of date, too.

> dictates my time be best spent leaving 0.4.8 happily running and working on
> other issues.

...which will make it more and more difficult for you to catch up.

> In any case if spi->spi_rpbase is set, it tells the CPM where the start of
> the SPI parameter RAM is, with respect to the start of the DPRAM, and by
> default it ain't 0x0.

Ummm... what _exactly_ is the sort  of  problem  you  have  with  the
current code?

> So with a small test, I replaced the statement with the default SPI offset
>       spi->spi_rpbase = 0x1D80;
> The CPM has a much happier time dealing with this than 0x0.

AFAICT the CPM has little to do  with  that;  if  my  suspicions  are
correct,  your  problems  only  show  up  when  using  some other SPI
drivers, like in Linux?

Normally, Linux driver code will look like this:

	/* Check for and use a microcode relocation patch. */
	if (spi->spi_rpbase)
		spi = (spi_t *)&cpmp->cp_dpmem[spi->spi_rpbase];
	printk("cpm_spi: using microcode patch (spi_rpbase=0x%p)\n", spi);

Note that this code requires that spi_rpbase is initialized to 0 when
no uCode patch is applied. And  it  seems  to  work  fine  on  allour
systems that use SPI.

> My original post is simply to warn people who are still using version
> 0.4.8. If someone has the time to check out the latest version of the code
> please feel free to do so.

This part of the code has not changed. Yet I don't see the problem.

Best regards,

Wolfgang Denk

Software Engineering:  Embedded and Realtime Systems,  Embedded Linux
Phone: (+49)-8142-4596-87  Fax: (+49)-8142-4596-88  Email: wd at denx.de
"355/113 -- Not the famous irrational number PI,  but  an  incredible

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