netdev - Re: [PATCH V1 3/3] net/mlx4_en: Add HW timestamping (TS) support

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Date:	Wed, 10 Oct 2012 05:37:03 +0200
From:	Richard Cochran <richardcochran@...il.com>
To:	Or Gerlitz <ogerlitz@...lanox.com>
Cc:	davem@...emloft.net, netdev@...r.kernel.org,
	Eugenia Emantayev <eugenia@...lanox.com>
Subject: Re: [PATCH V1 3/3] net/mlx4_en: Add HW timestamping (TS) support

On Tue, Oct 09, 2012 at 05:20:13PM +0200, Or Gerlitz wrote:

> diff --git a/drivers/net/ethernet/mellanox/mlx4/en_netdev.c b/drivers/net/ethernet/mellanox/mlx4/en_netdev.c
> index edd9cb8..ac78127 100644
> --- a/drivers/net/ethernet/mellanox/mlx4/en_netdev.c
> +++ b/drivers/net/ethernet/mellanox/mlx4/en_netdev.c

...

> @@ -1542,6 +1611,7 @@ static const struct net_device_ops mlx4_netdev_ops = {
>  	.ndo_set_mac_address	= mlx4_en_set_mac,
>  	.ndo_validate_addr	= eth_validate_addr,
>  	.ndo_change_mtu		= mlx4_en_change_mtu,
> +	.ndo_do_ioctl		= mlx4_en_ioctl,
>  	.ndo_tx_timeout		= mlx4_en_tx_timeout,
>  	.ndo_vlan_rx_add_vid	= mlx4_en_vlan_rx_add_vid,
>  	.ndo_vlan_rx_kill_vid	= mlx4_en_vlan_rx_kill_vid,

You should also provide a get_ts_info function to let the users know
about the device's time stamping capabilities.

> diff --git a/drivers/net/ethernet/mellanox/mlx4/en_timestamp.c b/drivers/net/ethernet/mellanox/mlx4/en_timestamp.c
> new file mode 100644
> index 0000000..783d493
> --- /dev/null
> +++ b/drivers/net/ethernet/mellanox/mlx4/en_timestamp.c

...

> +void mlx4_en_init_timestamp(struct mlx4_en_dev *mdev)
> +{
> +	struct mlx4_dev *dev = mdev->dev;
> +	u64 temp_mult;
> +
> +	memset(&mdev->cycles, 0, sizeof(mdev->cycles));
> +	mdev->cycles.read = mlx4_en_read_clock;
> +	mdev->cycles.mask = CLOCKSOURCE_MASK(48);
> +
> +	/* we have hca_core_clock in MHz, so to translate cycles to nsecs
> +	 * we need to divide cycles by freq and multiply by 1000;
> +	 * in order to get precise result we shift left the value,
> +	 * since we don't have floating point there;
> +	 * at the end shift result back
> +	 */
> +	temp_mult = ((1ull * 1000) << 29) / dev->caps.hca_core_clock;
> +	mdev->cycles.mult = (u32)temp_mult;
> +	mdev->cycles.shift = 29;
> +
> +	timecounter_init(&mdev->clock, &mdev->cycles,
> +			 ktime_to_ns(ktime_get_real()));

I didn't see any watchdog code to read this clock periodically, in
order to catch overflows.

Thanks,
Richard
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