linux-kernel - Re: [PATCH] x86_64: Add memcpy32

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Date:	Tue, 09 Sep 2014 10:01:18 +0200
From:	Clemens Ladisch <clemens@...isch.de>
To:	"Subhransu S. Prusty" <subhransu.s.prusty@...el.com>
CC:	hpa@...or.com, tglx@...utronix.de, mingo@...hat.com,
	x86@...nel.org, linux-kernel@...r.kernel.org, vinod.koul@...el.com
Subject: Re: [PATCH] x86_64: Add memcpy32_toio to write to PCI MMIO

Subhransu S. Prusty wrote:
> This is needed because the hardware

Which hardware?  Every x86-64 CPU ever built by AMD, Intel, and VIA?

> does not support 64-bit moveq insructions while writing to PCI MMIO.

> +#ifndef CONFIG_X86_64
> +#define MEMCPY_TOIO memcpy_toio
> +#else
> +#define MEMCPY_TOIO memcpy32_toio
> +#endif

This does not change any code that uses memcpy_toio().

> +	for (i = 0; i < count/sizeof(u32); i++)
> +		writel(*src_32++, dst_32++);

This breaks when count is not a multiple of four.


Regards,
Clemens
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