netdev - Re: [PATCH net v5] sfc: PIO:Restrict to 64bit arch and use 64-bit writes.

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Date:	Tue, 10 Jun 2014 23:32:00 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	sshah@...arflare.com
Cc:	netdev@...r.kernel.org, linux-net-drivers@...arflare.com
Subject: Re: [PATCH net v5] sfc: PIO:Restrict to 64bit arch and use 64-bit
 writes.

From: Shradha Shah <sshah@...arflare.com>
Date: Fri, 6 Jun 2014 19:24:01 +0100

> +/* Hardware issue requires that only 64-bit naturally aligned writes
> + * are seen by hardware.
> + */
> +#if BITS_PER_LONG == 64
> +/* not strictly necessary to restrict to x86 arch, but done for safety
> + * since unusual write combining behaviour can break PIO.
> + */
> +#ifdef CONFIG_X86_64
>  /* PIO is a win only if write-combining is possible */
>  #ifdef ARCH_HAS_IOREMAP_WC
>  #define EFX_USE_PIO 1
>  #endif
> +#endif
> +#endif

Just restrict this plainly to X86_64, the 64-bit test is completely
redundant.  It's obvious that x86_64 is the only platform you care
about and plan on testing or caring about in any way, so just make
that explicit.

I'm sorry about giving you continually a hard time about this, but
this is really gross, platform specific, ugly hackery going on here
and I'm going to do whatever I can to minimize it's uglyness.

Thank you.
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