Re: [Issue report] drivers/ftgmac100: DHCP occasionally fails during boot up or link down/up

From: Heyi Guo <guoheyi@linux.alibaba.com>
To: Andrew Lunn <andrew@lunn.ch>
Cc: "David S. Miller" <davem@davemloft.net>,
	Jakub Kicinski <kuba@kernel.org>, Joel Stanley <joel@jms.id.au>,
	Benjamin Herrenschmidt <benh@kernel.crashing.org>,
	Dylan Hung <dylan_hung@aspeedtech.com>,
	netdev@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [Issue report] drivers/ftgmac100: DHCP occasionally fails during boot up or link down/up
Date: Thu, 17 Feb 2022 09:38:15 +0800	[thread overview]
Message-ID: <641b3e71-211d-bb48-52c3-e34eef28e508@linux.alibaba.com> (raw)
In-Reply-To: <YgwSAjGN2eWUpamo@lunn.ch>

Thanks for your advice; I'll take try :)

Heyi


在 2022/2/16 上午4:50, Andrew Lunn 写道:
> On Tue, Feb 15, 2022 at 02:38:51PM +0800, Heyi Guo wrote:
>> Hi,
>>
>> We are using Aspeed 2600 and found DHCP occasionally fails during boot up or
>> link down/up. The DHCP client is systemd 247.6 networkd. Our network device
>> is 2600 MAC4 connected to a RGMII PHY module.
>>
>> Current investigation shows the first DHCP discovery packet sent by
>> systemd-networkd might be corrupted, and sysmtemd-networkd will continue to
>> send DHCP discovery packets with the same XID, but no other packets, as
>> there is no IP obtained at the moment. However the server side will not
>> respond with this serial of DHCP requests, until it receives some other
>> packets. This situation can be recovered by another link down/up, or a "ping
>> -I eth0 xxx.xxx.xxx.xxx" command to insert some other TX packets.
>>
>> Navigating the driver code ftgmac.c, I've some question about the work flow
>> from link down to link up. I think the flow is as below:
>>
>> 1. ftgmac100_open() will enable net interface with ftgmac100_init_all(), and
>> then call phy_start()
>>
>> 2. When PHY is link up, it will call netif_carrier_on() and then adjust_link
>> interface, which is ftgmac100_adjust_link() for ftgmac100
> The order there is questionable. Maybe it should first call the adjust
> link callback, and then the netif_carrier_on(). However...
>
>> 3. In ftgmac100_adjust_link(), it will schedule the reset work
>> (ftgmac100_reset_task)
>>
>> 4. ftgmac100_reset_task() will then reset the MAC
> Because of this delayed reset, changing the order will not help this
> driver.
>
>> I found networkd will start to send DHCP request immediately after
>> netif_carrier_on() called in step 2, but step 4 will reset the MAC, which
>> may potentially corrupt the sending packet.
> What is not clear to my is why it is scheduling the work rather than
> just doing it. At least for adjust_link, it is in a context it can
> sleep. ftgmac100_set_ringparam() should also be able to
> sleep. ftgmac100_interrupt() cannot sleep, so it does need to schedule
> work.
>
> I would suggest you refactor ftgmac100_reset_task() into a function
> that actually does the reset, and a wrapper which takes a
> work_struct. adjust_link can then directly do the reset, which
> probably solves your problem.

> 	 Andrew