netdev - Re: [PATCH net-next V2 5/5] net/mlx4

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Date:	Mon, 22 Apr 2013 12:01:10 -0700
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Amir Vadai <amirv@...lanox.com>
Cc:	"David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
	Richard Cochran <richardcochran@...il.com>,
	Or Gerlitz <ogerlitz@...lanox.com>,
	Eugenia Emantayev <eugenia@...lanox.com>
Subject: Re: [PATCH net-next V2 5/5] net/mlx4_en: Add a service task

On Mon, 2013-04-22 at 14:56 +0300, Amir Vadai wrote:
> Add a service task to run tasks that needed to be executed periodically.
> Currently the only task is a watchdog to catch NIC clock overflow, to make
> timestamping accurate.
> Will move the statistics task into this framework in a later patch.
> 
> Signed-off-by: Amir Vadai <amirv@...lanox.com>
> ---
>  drivers/net/ethernet/mellanox/mlx4/en_clock.c  |   20 ++++++++++++++++++++
>  drivers/net/ethernet/mellanox/mlx4/en_netdev.c |   24 ++++++++++++++++++++++++
>  drivers/net/ethernet/mellanox/mlx4/mlx4_en.h   |    4 ++++
>  3 files changed, 48 insertions(+), 0 deletions(-)
> 
> diff --git a/drivers/net/ethernet/mellanox/mlx4/en_clock.c b/drivers/net/ethernet/mellanox/mlx4/en_clock.c
> index 6d8227d..c1982a4 100644
> --- a/drivers/net/ethernet/mellanox/mlx4/en_clock.c
> +++ b/drivers/net/ethernet/mellanox/mlx4/en_clock.c
> @@ -126,4 +126,24 @@ void mlx4_en_init_timestamp(struct mlx4_en_dev *mdev)
>  
>  	timecounter_init(&mdev->clock, &mdev->cycles,
>  			 ktime_to_ns(ktime_get_real()));
> +
> +	/* Calculate period in seconds to call the overflow watchdog. Doing
> +	 * that, by dividing the maximal cycles value in nano-seconds, convert
> +	 * it to seconds, and divide by 2 - to make sure counter is checked at
> +	 * least once every wrap around.
> +	 */
> +	mdev->overflow_period =
> +		cyclecounter_cyc2ns(&mdev->cycles,
> +				    mdev->cycles.mask) / 1000000 / 2;
> +}
> +

So this 1000000 looks like NSEC_PER_SEC/HZ ?

What if HZ=100 ?



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