Re: [Openocd-development] Getting rid of default jtag clock rate

[David B. <da...@pa...>]

--- On Sun, 12/5/10, Øyvind Harboe <oyv...@zy...> wrote:

> Does anyone have any objections to
> getting rid of the
> concept of a default JTAG clock rate?

NO.  But let's see a proposed patch ... :)

I recall some discussions a while back about
how JTAGKEY2 was broken because its driver was
embedding a default clock rate assumption,
which broke on some hardware.

There have also been related parport issues.

> 
> Basically, I'd like OpenOCD to refuse to start until the script defines the clock rate.

Script is the right place, yes.  Not *ANY* of
the adapter drivers, or embedded in OpenOCD
framework code either.


> The actual mechanism needs a bit of thought, because it
> is possible to set jtag clock rate in reset-start and in
> my
> book that counts as not using the default clock rate.

Right.  Reset sequences may need to re-clock, and
that's a key hook.  Changing SoC clocks tendds to
imply a need to update debug adapter clocks (be
they JTAG or something else).

Fancy reset sequences may end up initializing PLLs
and so forth.  Fixed clocks are going to break.

- Dave