[PATCH 2/2] ARM: use DEBUG_LL infrastructural for multiplatform uncompress debug

On Thu, Jan 17, 2013 at 04:25:42PM +0000, Arnd Bergmann wrote:

On Thursday 17 January 2013, Shawn Guo wrote:

quoted

However, there is a problem with above approach.  DEBUG_LL routines
will check MMU enable bit to decide whether physical or virtual address
should be used to access debug port.  In case virtual address needs
to be used, the address returned by addruart will not work for
decompressor who uses a different mapping from what kernel uses.
Fortunately, decompressor uses a flat mapping (same physical and virtual
addresses).  So we can easily work it around by asking platform addruart
return physical address as virtual address when it runs in decompressor.
The macro UNCOMPRESS_DEBUG is defined for this use.

Can't you just create a new copy of kernel/debug.S in boot/compressed/
that provides only a putc() function and uses the physical address
unconditionally?

Why did I not think of this?  The approach is obviously simpler.
Please check the updated version I just sent out.  Thanks.

Shawn