Hi Greg, On Thu, Nov 04, 2010 at 02:50:16PM +1000, Greg Ungerer wrote: > > Hi All, > > This is a request for testing (and comment) on a patch that will > use the separate kernel/user stack pointer hardware that the more > modern ColdFire cores have. This has a performance benefit when > used, the exception entry and exit paths are quite a few instructions > shorter.
Yeah, the mcf548x will benefit from that :) > > Currently the parts I know can use it are the 520[78], 523x, 527[12], > 527[45], 523x (and 547x/548x). > > The use of the separate stack pointer is based on a config option > (CONFIG_COLDFIRE_SW_A7) that is automatically selected based on > ColdFure CPU selection. This may well not be the best way to do this. > Maybe the selection should be based on the compiler define > __mcfisaaplus__. I didn't use this because only more modern toolchains > support it. My 4.2.4 based toolchain doesn't. I prefer to keep the choice explicit in kernel sources than to rely on gcc's defines. > > The older toolchain also required one more ugly hack. Pre 4.3 gcc > won't generate the "move usp" instructions required for this when > compiling for ColdFire. So I have had to hard code the opcode values > in place for these instructions for now. Technically, it is not gcc's job but gas's job. But it's not a problem to have some hex constants as long as they are documented. > > Maybe we need to bite the bullet and just not support this using > older toolchains... Thoughts? > > The patch below is against 2.6.36. If you prefer living on the edge, > you can pull this from from the for-linus branch of ther m68knommu > git tree (along with a bunch of other updates): > > git://git.kernel.org/pub/scm/linux/kernel/git/gerg/m68knommu.git for-linus > > Regards > Greg > > > --- > [PATCH] m68knommu: use user stack pointer hardware on some ColdFire cores > > The more modern ColdFire parts (even if based on older version cores) > have separate user and supervisor stack pointers (a7 register). > Modify the ColdFire CPU setup and exception code to enable and use > this on parts that have it. > > Signed-off-by: Greg Ungerer <g...@uclinux.org> > --- > m68k/include/asm/cacheflush_no.h | 4 +- > m68k/include/asm/entry_no.h | 59 > ++++++++++++++++++++---------------- > m68k/include/asm/mcfcache.h | 6 +-- > m68k/include/asm/processor.h | 13 ++++--- > m68knommu/Kconfig | 11 ++++++ > m68knommu/platform/coldfire/entry.S | 56 ++++++---------------------------- > 6 files changed, 68 insertions(+), 81 deletions(-) > > diff -Naurp linux-2.6.36/arch/m68k/include/asm/cacheflush_no.h > linux-2.6.36.eusp/arch/m68k/include/asm/cacheflush_no.h > --- linux-2.6.36/arch/m68k/include/asm/cacheflush_no.h 2010-10-21 > 06:30:22.000000000 +1000 > +++ linux-2.6.36.eusp/arch/m68k/include/asm/cacheflush_no.h 2010-11-04 > 14:32:46.491869598 +1000 > @@ -54,7 +54,7 @@ static inline void __flush_cache_all(voi > #endif /* CONFIG_M5407 */ > #if defined(CONFIG_M523x) || defined(CONFIG_M527x) > __asm__ __volatile__ ( > - "movel #0x81400100, %%d0\n\t" > + "movel #0x81400110, %%d0\n\t" Some symbolic constants would not hurt and would be easier for consistency with mcfcache.h. > "movec %%d0, %%CACR\n\t" > "nop\n\t" > : : : "d0" ); > @@ -82,7 +82,7 @@ static inline void __flush_cache_all(voi > #endif /* CONFIG_M5249 */ > #ifdef CONFIG_M532x > __asm__ __volatile__ ( > - "movel #0x81000200, %%d0\n\t" > + "movel #0x81000210, %%d0\n\t" > "movec %%d0, %%CACR\n\t" > "nop\n\t" > : : : "d0" ); > diff -Naurp linux-2.6.36/arch/m68k/include/asm/entry_no.h > linux-2.6.36.eusp/arch/m68k/include/asm/entry_no.h > --- linux-2.6.36/arch/m68k/include/asm/entry_no.h 2010-10-21 > 06:30:22.000000000 +1000 > +++ linux-2.6.36.eusp/arch/m68k/include/asm/entry_no.h 2010-11-04 > 14:32:46.491869598 +1000 > @@ -52,12 +52,16 @@ LENOSYS = 38 > */ > > #ifdef CONFIG_COLDFIRE > +#ifdef CONFIG_COLDFIRE_SW_A7 It would have been better to have a new positive define for the new functionality. > /* > - * This is made a little more tricky on the ColdFire. There is no > - * separate kernel and user stack pointers. Need to artificially > + * This is made a little more tricky on older ColdFires. There is no > + * separate supervisor and user stack pointers. Need to artificially > * construct a usp in software... When doing this we need to disable > - * interrupts, otherwise bad things could happen. > + * interrupts, otherwise bad things will happen. > */ Regards Philippe -- Philippe De Muyter phdm at macqel dot be Tel +32 27029044 Macq Electronique SA rue de l'Aeronef 2 B-1140 Bruxelles Fax +32 27029077 _______________________________________________ uClinux-dev mailing list uClinux-dev@uclinux.org http://mailman.uclinux.org/mailman/listinfo/uclinux-dev This message was resent by uclinux-dev@uclinux.org To unsubscribe see: http://mailman.uclinux.org/mailman/options/uclinux-dev
