Subject: Re: [PATCH net v4 1/2] sfc: use 64-bit writes for PIO.

From: Sergei Shtylyov <[email-masked]>
Date: Tue, 03 Jun 2014 20:45:35 +0400

Hello.

On 06/03/2014 02:04 PM, Shradha Shah wrote:

> From: Jon Cooper <[email-masked]>

> Patch to open-code the memory copy routines.
> 32bit writes over the PCI bus causes data corruption.

> Fixes:ee45fd92c739
> ("sfc: Use TX PIO for sufficiently small packets")

> Signed-off-by: Shradha Shah <[email-masked]>
> ---
>   drivers/net/ethernet/sfc/tx.c | 24 +++++++++++++++++++-----
>   1 file changed, 19 insertions(+), 5 deletions(-)

> diff --git a/drivers/net/ethernet/sfc/tx.c b/drivers/net/ethernet/sfc/tx.c
> index fa94753..d2c9ca0 100644
> --- a/drivers/net/ethernet/sfc/tx.c
> +++ b/drivers/net/ethernet/sfc/tx.c
> @@ -189,6 +189,20 @@ struct efx_short_copy_buffer {
>   	u8 buf[L1_CACHE_BYTES];
>   };
>
> +/* Copy in explicit 64-bit writes. */
> +static void efx_memcpy_64(void __iomem *dest, void *src, size_t len)
> +{
> +	u64 *src64 = src, __iomem *dest64 = dest;
> +	size_t i, l64 = len / 8;
> +
> +	WARN_ON_ONCE(len % 8 != 0);
> +	WARN_ON_ONCE(((u8 __iomem *)dest - (u8 __iomem *)0) % 8 != 0);
> +	BUILD_BUG_ON(sizeof(uint64_t) != 8);
> +
> +	for (i = 0; i < l64; ++i)
> +		writeq(src64[i], dest64+i);

    Could you please surround + by spaces for consistency?

> +}
> +

WBR, Sergei