[Letux-kernel] 1.5GHz problems

Matthijs van Duin matthijsvanduin at gmail.com
Tue Aug 2 09:52:45 CEST 2016

On 2 August 2016 at 08:45, H. Nikolaus Schaller <hns at goldelico.com> wrote:
> So they should be modified dynamically when switching CPU frequencies?

Yes, and the datasheet seems quite emphatic about it. See section
4.2.1 of the omap5 TRM and the large note at the end of section 4.3.2
(Operating Performance Points -> MPU) of the omap5432 datasheet.

(Random side note: the same restriction apparently applies to
AM57xx/DRA7xx based on section 4.2.1 of its TRM, although it's not
waved in your face as much as on the omap5.)

> Unfortunately I neither have JTAG equipment nor do we have access to the
> JTAG interface on the Pyra CPU board. Since neither is needed in normal
> situations. For a big pile of money we could have built some Pyra CPU
> boards where these signals are made available on external test points.

Ouch. You can get a perfectly adequate JTAG debugger (e.g. XDS100v2)
for less than $100, but not having JTAG pinned out is a problem.

I read in the TRM that JTAG can alternatively be muxed to the SD card
slot pins (intended for space-constrained applications like
smartphones). I have no idea however whether that needs any special
config other than setting the pinmux.


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