Messages in this thread | | | From | Geert Uytterhoeven <> | Date | Fri, 14 Jun 2019 16:49:45 +0200 | Subject | Re: [PATCH] m68k: io: Fix io{read,write}{16,32}be() for Coldfire peripherals |
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Hi Arnd,
On Mon, Apr 29, 2019 at 2:40 PM Arnd Bergmann <arnd@arndb.de> wrote: > On Mon, Apr 29, 2019 at 10:19 AM Geert Uytterhoeven > <geert@linux-m68k.org> wrote: > > The generic definitions of mmio_{read,write}{16,32}be() in lib/iomap.c > > assume that the {read,write}[wl]() I/O accessors always use little > > endian accesses, and swap the result. > > > > However, the Coldfire versions of the {read,write}[wl]() I/O accessors are > > special, in that they use native big endian instead of little endian for > > accesses to the on-SoC peripheral block, thus violating the assumption. > > > > Fix this by providing our own variants, using the raw accessors, > > reinstating the old behavior. This is fine on m68k, as no special > > barriers are needed, and also avoids swapping data twice. > > > > Reported-by: Angelo Dureghello <angelo@sysam.it> > > Fixes: aecc787c06f4300f ("iomap: Use non-raw io functions for io{read|write}XXbe") > > Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org> > > --- > > This can be reverted later, after this oddity of the Coldfire I/O > > support has been fixed, and drivers have been updated. > > --- > > arch/m68k/include/asm/io.h | 6 ++++++ > > 1 file changed, 6 insertions(+) > > > > diff --git a/arch/m68k/include/asm/io.h b/arch/m68k/include/asm/io.h > > index aabe6420ead2a599..d47e7384681ab1cd 100644 > > --- a/arch/m68k/include/asm/io.h > > +++ b/arch/m68k/include/asm/io.h > > @@ -8,6 +8,12 @@ > > #include <asm/io_mm.h> > > #endif > > > > +#define mmio_read16be(addr) __raw_readw(addr) > > +#define mmio_read32be(addr) __raw_readl(addr) > > + > > +#define mmio_write16be(val, port) __raw_writew((val), (port)) > > +#define mmio_write32be(val, port) __raw_writel((val), (port)) > > + > > #include <asm-generic/io.h> > > This looks correct to me, but there are two points that stick out to me: > > - why do you only do this for mmio and not for pio?
Because no one had a need for it? ;-)
Now seriously, m68k only has MMIO, no PIO. Any PIO, if used, is for ISA or PCMCIA I/O accesses, which are little endian.
> - why do you even use the generic_iomap wrappers rather than > the trivial asm-generic versions of those functions?
Looking at git history, that was done to fix some link errors, which no longer seem to happen with the more mature asm-generic infrastructure we have now.
So probably we can drop the selection of GENERIC_IOMAP and inclusion of <asm-generic/iomap.h>, after fixing a few compiler warnings like:
include/asm-generic/io.h: In function ‘ioread8_rep’ arch/m68k/include/asm/io_mm.h:371:44: warning: passing argument 1 of ‘raw_insb’ discard ‘const’ qualifier from pointer target type [-Wdiscarded-qualifiers] #define readsb(port, buf, nr) raw_insb((port), (u8 *)(buf), (nr)) arch/m68k/include/asm/raw_io.h:101:50: note: expected ‘volatile u8 *’ {aka ‘volatile unsigned char *’} but argument is of type ‘const volatile void *’ static inline void raw_insb(volatile u8 __iomem *port, u8 *buf, unsigned int len)
and some regression testing, of course.
Gr{oetje,eeting}s,
Geert
-- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org
In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds
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