[PATCH] serial: DCC(JTAG) serial and console emulation support

Tony Lindgren tony at atomide.com
Fri Oct 8 16:58:55 EDT 2010

* Tony Lindgren <tony at atomide.com> [101008 13:24]:
> * Nicolas Pitre <nico at fluxnic.net> [101007 18:16]:
> > On Thu, 7 Oct 2010, Tony Lindgren wrote:
> > > 
> > > Can you please pass the read and write functions to the driver
> > > in platform_data? We are already booting kernels with both
> > > ARMv6 and 7 compiled in.
> > 
> > No.  This has nothing to do with platform as this can be determined 
> > within the driver itself.  Would be much better to simply determine 
> > which flavor to use at driver init time and assign two function pointers.
> In the long run some platform init code is needed for powering
> up the JTAG interface and take care of pin multiplexing etc.
> Also, isn't DCC (Debug Communications Channel) a JTAG standard? At least
> the following does not say anything about DCC being ARM specific:
> http://en.wikipedia.org/wiki/Joint_Test_Action_Group
> BTW, we already have ETM (Embedded Trace Module) in arch/arm/kernel/etm.c.
> That is set up as amba driver.

Hmm, then again it says this about the scan chains:

  "SCAN_N ... ARM instruction to select the numbered scan chain used
  with EXTEST or INTEST. There are six scan chains"

Which seems like these scan chains are ARM specific.



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