On Wed, May 30, 2012 at 01:20:02PM +0200, Geert Uytterhoeven wrote: > On Wed, May 30, 2012 at 12:22 PM, Philippe De Muyter <[email protected]> wrote: > > On Tue, May 29, 2012 at 11:33:36PM +0200, Geert Uytterhoeven wrote: > >> Signed-off-by: Geert Uytterhoeven <[email protected]> > >> --- > >> Do we also want > >> > >> select HAVE_EFFICIENT_UNALIGNED_ACCESS if (!COLDFIRE && !M68000) > > > > Sorry, I did not follow what happened to unaligned accesses, but > > CPU32 family (at least 68340) crashes on unaligned accesses. > > We don't seem to have CONFIG_M68340 in arch/m68k/Kconfig.cpu?
I have a local port here (but based on an ancient linux kernel, 2.6.2 IIRC) > But Freescale's website confirms both 68340 and 68360 are CPU32. > > arch/m68k/include/asm/unaligned.h assumes CPU32 (CONFIG_MCPU32) > can do unaligned accesses: That's not true. Accessing a 16- or 32-bit word at an odd address with a 68340 generates an Address Error Exception. I remember discovering a bug in the ppp kernel code because of that. > > #if defined(CONFIG_COLDFIRE) || defined(CONFIG_M68000) > #include <linux/unaligned/be_struct.h> > #include <linux/unaligned/le_byteshift.h> > #include <linux/unaligned/generic.h> > > #define get_unaligned __get_unaligned_be > #define put_unaligned __put_unaligned_be > > #else > /* > * The m68k can do unaligned accesses itself. > */ > #include <linux/unaligned/access_ok.h> > #include <linux/unaligned/generic.h> > > #define get_unaligned __get_unaligned_be > #define put_unaligned __put_unaligned_be > > #endif > > Is this wrong? I can't tell from reading just the lines above, but I think one should add "|| defined(CONFIG_MCPU32)" at the end of the if condition. I also think that the Coldfire 5272 can do unaligned accesses, but I cannot test that at the moment. > > However, for CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS, > the question is not whether unaligned accesses are supported, but > whether they are more efficient than byte copies when copying larger blocks. OK, thanks Philippe -- Philippe De Muyter +32 2 6101532 Macq SA rue de l'Aeronef 2 B-1140 Bruxelles -- To unsubscribe from this list: send the line "unsubscribe linux-m68k" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
