On Wed, 6 May 2015, Russell King - ARM Linux wrote:
> On Tue, Apr 28, 2015 at 11:28:53AM -0400, Nicolas Pitre wrote:
> > On Tue, 28 Apr 2015, Russell King - ARM Linux wrote:
> >
> > > On Fri, Apr 24, 2015 at 03:46:56PM +0200, Geert Uytterhoeven wrote:
> > > > So please optimize ARM's _memcpy_fromio(), _memcpy_toio(), and
> > > > _memset_io().
> > > > That will benefit other drivers on ARM, too.
> > >
> > > That's not going to happen.
> > >
> > > I've had a patch which does that, but people are concerned that it changes
> > > the behaviour of the functions by changing the access size, which could
> > > cause regressions. It seems people are far too worried about that to even
> > > consider trying. :(
> >
> > What about making the optimized implementation available via kconfig?
>
> I'd prefer not to. My personal feeling is to put the patch in and just be
> done with it - these functions are supposed to be used on IO areas which
> don't care about access size (in other words, are memory-like rather than
> being register-like.) Here's the rather old patch:
>
> From: Russell King <rmk+ker...@arm.linux.org.uk>
> Subject: [PATCH] ARM: optimize memset_io()/memcpy_fromio()/memcpy_toio()
>
> If we are building for a LE platform, and we haven't overriden the
> MMIO ops, then we can optimize the mem*io operations using the
> standard string functions.
>
> Signed-off-by: Russell King <rmk+ker...@arm.linux.org.uk>
Acked-by: Nicolas Pitre <n...@linaro.org>
> ---
> arch/arm/include/asm/io.h | 25 +++++++++++++++++++++++++
> 1 file changed, 25 insertions(+)
>
> diff --git a/arch/arm/include/asm/io.h b/arch/arm/include/asm/io.h
> index d070741b2b37..358c8206419b 100644
> --- a/arch/arm/include/asm/io.h
> +++ b/arch/arm/include/asm/io.h
> @@ -23,6 +23,7 @@
>
> #ifdef __KERNEL__
>
> +#include <linux/string.h>
> #include <linux/types.h>
> #include <asm/byteorder.h>
> #include <asm/memory.h>
> @@ -312,9 +313,33 @@ extern void _memset_io(volatile void __iomem *, int,
> size_t);
> #define writesw(p,d,l) __raw_writesw(p,d,l)
> #define writesl(p,d,l) __raw_writesl(p,d,l)
>
> +#ifndef __ARMBE__
> +static inline void memset_io(volatile void __iomem *dst, unsigned c,
> + size_t count)
> +{
> + memset((void __force *)dst, c, count);
> +}
> +#define memset_io(dst,c,count) memset_io(dst,c,count)
> +
> +static inline void memcpy_fromio(void *to, const volatile void __iomem *from,
> + size_t count)
> +{
> + memcpy(to, (const void __force *)from, count);
> +}
> +#define memcpy_fromio(to,from,count) memcpy_fromio(to,from,count)
> +
> +static inline void memcpy_toio(volatile void __iomem *to, const void *from,
> + size_t count)
> +{
> + memcpy((void __force *)to, from, count);
> +}
> +#define memcpy_toio(to,from,count) memcpy_toio(to,from,count)
> +
> +#else
> #define memset_io(c,v,l) _memset_io(c,(v),(l))
> #define memcpy_fromio(a,c,l) _memcpy_fromio((a),c,(l))
> #define memcpy_toio(c,a,l) _memcpy_toio(c,(a),(l))
> +#endif
>
> #endif /* readl */
>
> --
> 1.8.3.1
>
>
>
> --
> FTTC broadband for 0.8mile line: currently at 10.5Mbps down 400kbps up
> according to speedtest.net.
>
>
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
