[PATCH] MTD: Fix Orion NAND driver compilation with ARM OABI

[Mikael Pettersson]

David Woodhouse writes:
 > On Sat, 2010-03-20 at 13:20 +0200, Paulius Zaleckas wrote:
 > > On Sat, Mar 20, 2010 at 11:41 AM, David Woodhouse <dwmw2 at infradead.org> wrote:
 > > > On Sat, 2010-03-20 at 10:55 +0200, Paulius Zaleckas wrote:
 > > >> -             uint64_t x;
 > > >> +             /*
 > > >> +              * force x variable to r2/r3 registers since ldrd instruction
 > > >> +              * requires first register to be even.
 > > >> +              */
 > > >> +             register uint64_t x asm ("r2");
 > > >> +
 > > >>               asm volatile ("ldrd\t%0, [%1]" : "=&r" (x) : "r" (io_base));
 > > >
 > > > Hm, isn't there an asm constraint which will force it into an
 > > > appropriate register pair?
 > > 
 > > Not that I know of...
 > > 
 > > > Failing that, "=&r2,r4,r6,r8" ought to work.
 > > 
 > > No, fails with error: matching constraint not valid in output operand
 > 
 > Hm, crap -- GCC on ARM doesn't let you give specific registers, so that
 > trick doesn't work.

I missed the start of this thread, but looking at orion_nand.c I fail to
see why you'd need to mess with inline asm for reading a sequence of u64
values from an I/O location to an array.

Rewriting that to proper C generates a nice ldrd;strd loop with my gcc-4.4.3.