Re: pxa2xx_spi with SFRM

[David Brownell <david-b-yBeKhBN/0LDR7s880joybQ@public.gmane.org>]

On Friday 15 August 2008, Vernon Sauder wrote:
> >I think the  "1" and "15" above correspond to threshold register values
> >of "0" and "14"; that is the above numbers are the number of words in
> >the FIFO that trigger the interrupt/service request.
> 
> All this still leaves me slightly confused. (And I didn't even touch the
> dma_burst_size member yet.) I assume that the correct value for all of
> these settings must be determined empirically, not just theoretically.

I think you're probably right, although I'd say "optimum" not "correct".
Incorrect values should be rejected (or at least ignored) by the driver.


> How can I tell what the correct or optimum values are? Do I just use a
> performance test on the Flash chip or MMC device? Or can I look at the
> logic analyzer output and see what they should be? Or is there a debug
> printk that needs to be enabled?

I think the idea was that since the PXA hardware manuals don't
offer suggestions, this was a "punt it all to the board maintainer"
kind of solution.

- dave


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