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

[Shawn Guo]

On Thu, Jan 17, 2013 at 04:25:42PM +0000, Arnd Bergmann wrote:
> On Thursday 17 January 2013, Shawn Guo wrote:
> > 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