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

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Date:	Fri, 18 Apr 2014 21:17:52 +0800
From:	zhangfei <zhangfei.gao@...aro.org>
To:	David Miller <davem@...emloft.net>
CC:	linux@....linux.org.uk, arnd@...db.de, f.fainelli@...il.com,
	sergei.shtylyov@...entembedded.com, mark.rutland@....com,
	David.Laight@...LAB.COM, eric.dumazet@...il.com,
	linux-arm-kernel@...ts.infradead.org, netdev@...r.kernel.org,
	devicetree@...r.kernel.org
Subject: Re: [PATCH 3/3] net: hisilicon: new hip04 ethernet driver

Dear David

On 04/08/2014 02:53 AM, David Miller wrote:

>> +static void hip04_tx_reclaim(struct net_device *ndev, bool force)
>   ...
>> +static void hip04_xmit_timer(unsigned long data)
>> +{
>> +	struct net_device *ndev = (void *) data;
>> +
>> +	hip04_tx_reclaim(ndev, false);
>> +}
>   ...
>> +	mod_timer(&priv->txtimer, jiffies + RECLAIM_PERIOD);
>
> And this is where I stop reading your driver, I've stated already that this
> kind of reclaim scheme is unacceptable.
>
> The kernel timers lack the granularity necessary to service TX reclaim
> with a reasonable amount of latency.
>
> You must use some kind of hardware notification of TX slots becomming
> available, I find it totally impossible that a modern ethernet controller
> was created without a TX done interrupt.
>

There is no tx_done interrupt, we may need some workaround.

Is it acceptable to use poll to reclaim the xmitted buffer.
And in the xmit calling napi_schedule.

Thanks
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