From: Larry Martin <Larry@GlueLogix.com> - 2010-09-21 01:11:48
Is it possible to slow down the MMC clock on the Verdex Pro?
In connection with this post about intermittent SDIO errors:
I am trying to slow down the MMC clock and/or downclock the PXA. I have
a 'scope on the 20 MHz MMC clock. It does not change when I run
"pxaregs CCCR 0x0208" or "pxaregs CCCR 0x0201". I cannot see any other
likely registers in the Marvell docs, and have not been able to build a
version of cpufreq for Verdex.
I will be reading the mmc driver source, but was hoping someone might
From: Ash Charles <ashcharles@gm...> - 2010-09-21 14:05:08
On Mon, Sep 20, 2010 at 6:11 PM, Larry Martin <Larry@...> wrote:
> "pxaregs CCCR 0x0208" or "pxaregs CCCR 0x0201". I cannot see any other
> likely registers in the Marvell docs, and have not been able to build a
> version of cpufreq for Verdex.
I think you've found the right register but the only way I've been
able to change it is on reset; I'm not sure if this is a hardware
restriction or simply a product of how I've been doing things.
Essentially, I've just changed the value of CCCR in the u-boot source.
If you don't feel like grokking u-boot and you want to run an XL6P at
400MHz, you should be able to use the 400MHz u-boot
(http://www.gumstix.net/feeds/) instead of the 600MHz version---it
looks like the CCCR_VAL in <u-boot top>/include/configs/gumstix.h is
the only difference (be aware that it is possible to brick your Verdex
as you are replacing u-boot).
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