netdev - Re: [PATCH net-next v13 3/3] net: hisilicon: new hip04 ethernet driver

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Date:	Thu, 15 Jan 2015 10:53:46 +0100
From:	Arnd Bergmann <arnd@...db.de>
To:	linux-arm-kernel@...ts.infradead.org
Cc:	Ding Tianhong <dingtianhong@...wei.com>, robh+dt@...nel.org,
	davem@...emloft.net, grant.likely@...aro.org, agraf@...e.de,
	devicetree@...r.kernel.org, linux@....linux.org.uk,
	sergei.shtylyov@...entembedded.com, eric.dumazet@...il.com,
	netdev@...r.kernel.org, xuwei5@...ilicon.com,
	zhangfei.gao@...aro.org
Subject: Re: [PATCH net-next v13 3/3] net: hisilicon: new hip04 ethernet driver

On Wednesday 14 January 2015 14:34:14 Ding Tianhong wrote:
> +static int hip04_set_coalesce(struct net_device *netdev,
> +                             struct ethtool_coalesce *ec)
> +{
> +       struct hip04_priv *priv = netdev_priv(netdev);
> +
> +       /* Check not supported parameters  */
> +       if ((ec->rx_max_coalesced_frames) || (ec->rx_coalesce_usecs_irq) ||
> +           (ec->rx_max_coalesced_frames_irq) || (ec->tx_coalesce_usecs_irq) ||
> +           (ec->use_adaptive_rx_coalesce) || (ec->use_adaptive_tx_coalesce) ||
> +           (ec->pkt_rate_low) || (ec->rx_coalesce_usecs_low) ||
> +           (ec->rx_max_coalesced_frames_low) || (ec->tx_coalesce_usecs_high) ||
> +           (ec->tx_max_coalesced_frames_low) || (ec->pkt_rate_high) ||
> +           (ec->tx_coalesce_usecs_low) || (ec->rx_coalesce_usecs_high) ||
> +           (ec->rx_max_coalesced_frames_high) || (ec->rx_coalesce_usecs) ||
> +           (ec->tx_max_coalesced_frames_irq) ||
> +           (ec->stats_block_coalesce_usecs) ||
> +           (ec->tx_max_coalesced_frames_high) || (ec->rate_sample_interval))
> +               return -EOPNOTSUPP;
> +
> +       if ((ec->tx_coalesce_usecs > HIP04_MAX_TX_COALESCE_USECS ||
> +            ec->tx_coalesce_usecs < HIP04_MIN_TX_COALESCE_USECS) ||
> +           (ec->tx_max_coalesced_frames > HIP04_MAX_TX_COALESCE_FRAMES ||
> +            ec->tx_max_coalesced_frames < HIP04_MIN_TX_COALESCE_FRAMES))
> +               return -EINVAL;
> +
> +       priv->tx_coalesce_usecs = ec->tx_coalesce_usecs;
> +       priv->tx_coalesce_frames = ec->tx_max_coalesced_frames;
> +
> +       return 0;
> +}

I just looked at this again and noticed that you fail to actually use the
tx_coalesce_usecs value anywhere, since you don't call hrtimer_set_expires_range()
any more.

Also, I guess it would be nice use the rx_coalesce_usecs_low and
tx_coalesce_usecs_high numbers instead of just a single number, as
hrtimer_set_expires_range takes two values already. Just do something
like 

	hrtimer_set_expires_range(&priv->tx_coalesce_timer,
				   priv->rx_coalesce_usecs_low,
				   priv->rx_coalesce_usecs_high -
				   priv->rx_coalesce_usecs_low);

and make sure the 'low' value is smaller than the 'high' one.

> +       priv->tx_coalesce_frames = TX_DESC_NUM * 3 / 4;
> +       priv->tx_coalesce_usecs = 200;

Related, instead of putting the raw numbers here, how about
adding the defaults along with the other macros we talked about:

#define HIP04_MAX_TX_COALESCE_USECS		10000
#define HIP04_MIN_TX_COALESCE_USECS		1
#define HIP04_MAX_TX_COALESCE_FRAMES		(TX_DESC_NUM - 1)
#define HIP04_MIN_TX_COALESCE_FRAMES		1

#define HIP04_DEFAULT_TX_COALESCE_USECS_LOW	80
#define HIP04_DEFAULT_TX_COALESCE_USECS_HIGH	200
#define HIP04_DEFAULT_TX_COALESCE_FRAMES	(TX_DESC_NUM / 2)

	Arnd
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