Re: [PATCH] m68knommu: allow ColdFire CPUs to use unaligned accesses

[Philippe De Muyter <phdm@macqel.be>]

On Fri, Jun 08, 2012 at 03:43:00PM +1000, gerg@snapgear.com wrote:
> From: Greg Ungerer <gerg@uclinux.org>
> 
> All current ColdFire CPUs are able to support unaligned memory accesses.
> So remove the CONFIG_CPU_HAS_NO_UNALIGNED option selection for ColdFire.
> 
> It seems that the current restriction was inherrited from the early non-MMU
> support for the basic 68000 proecssors - which do not support unaligned
> accesses.

It seems that the first ColdFires needed the restriction :

I read in the "MCF5200 ColdFire Family Programmer’s Reference Manual" :

The ColdFire processor default configuration supports word- and
longword-sized operand references on 0-modulo-2 and 0-modulo-4
addresses, respectively. All other references are defined as
misaligned accesses. Any attempt to access a misaligned operand
generates an address-error exception, unless the optional hardware
module for handling misalignment is present. This misalignment
module converts any misaligned operand references into a series
of aligned bus cycles to access the data. The existence of the
misalignment module is implementation-dependent and is documented
in the appropriate ColdFire user’s manual.

Philippe