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

[Nicolas Pitre]

On Fri, 8 Oct 2010, Tony Lindgren wrote:

> * 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.

Or ETM specific even.


Nicolas