Hi Philippe,
On 08/06/12 23:35, Philippe De Muyter wrote:
On Fri, Jun 08, 2012 at 10:19:43PM +1000, Greg Ungerer wrote:
Hi Philippe,
On 06/08/2012 08:39 PM, Philippe De Muyter wrote:
On Fri, Jun 08, 2012 at 03:43:00PM +1000, g...@snapgear.com wrote:
From: Greg Ungerer<g...@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 ProgrammerÆs 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 userÆs manual.
I mentionned that only to make you able to soften the commit comment :)
Ok, makes sense. I should probably have mentioned that this means
the ColdFire processors currently support by Linux :-)
Something like:
All of the current Linux supported ColdFire CPUs handle unaligned
memory accesses. So remove the CONFIG_CPU_HAS_NO_UNALIGNED option
selection for ColdFire. If we ever support a specific ColdFire CPU
that does not support unaligned accesses then we can insert the
CONFIG_CPU_HAS_NO_UNALIGNED for that specific CPU type.
I wish Freescale really did make that clear within the doco for each
part!
The oldest (and I assume simplest) part we support is the 5206, and it
does explicitly state in the MCF5206UM that it supports unaligned
accesses (Section 6.6). It is not as clear as this in some of the
other CPU/SoC User Manuals that I looked through.
I am pretty confident that all the parts we currently support in Linux
do unaligned accesses.
I agree. And if some parts did not implement it, we'd see it quickly.
Yep.
Regards
Greg
------------------------------------------------------------------------
Greg Ungerer -- Principal Engineer EMAIL: g...@snapgear.com
SnapGear Group, McAfee PHONE: +61 7 3435 2888
8 Gardner Close FAX: +61 7 3217 5323
Milton, QLD, 4064, Australia WEB: http://www.SnapGear.com
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