From: liuyonglong <liuyonglong@huawei.com>
To: Heiner Kallweit <hkallweit1@gmail.com>, <andrew@lunn.ch>,
<davem@davemloft.net>
Cc: <netdev@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
<linuxarm@huawei.com>, <salil.mehta@huawei.com>,
<yisen.zhuang@huawei.com>, <shiju.jose@huawei.com>
Subject: Re: [RFC] net: phy: read link status twice when phy_check_link_status()
Date: Wed, 31 Jul 2019 13:58:41 +0800 [thread overview]
Message-ID: <9dd4fe9f-5ee5-23a6-14bf-a5d644567d27@huawei.com> (raw)
In-Reply-To: <5634113b-f5b5-6fa8-851d-1402e046c3df@gmail.com>
On 2019/7/31 13:44, Heiner Kallweit wrote:
> On 31.07.2019 05:33, liuyonglong wrote:
>>
>>
>> On 2019/7/31 3:04, Heiner Kallweit wrote:
>>> On 30.07.2019 08:35, liuyonglong wrote:
>>>> :/sys/kernel/debug/tracing$ cat trace
>>>> # tracer: nop
>>>> #
>>>> # entries-in-buffer/entries-written: 45/45 #P:128
>>>> #
>>>> # _-----=> irqs-off
>>>> # / _----=> need-resched
>>>> # | / _---=> hardirq/softirq
>>>> # || / _--=> preempt-depth
>>>> # ||| / delay
>>>> # TASK-PID CPU# |||| TIMESTAMP FUNCTION
>>>> # | | | |||| | |
>>>> kworker/64:2-1028 [064] .... 172.295687: mdio_access: mii-0000:bd:00.0 read phy:0x01 reg:0x02 val:0x001c
>>>> kworker/64:2-1028 [064] .... 172.295726: mdio_access: mii-0000:bd:00.0 read phy:0x01 reg:0x03 val:0xc916
>>>> kworker/64:2-1028 [064] .... 172.296902: mdio_access: mii-0000:bd:00.0 read phy:0x01 reg:0x01 val:0x79ad
>>>> kworker/64:2-1028 [064] .... 172.296938: mdio_access: mii-0000:bd:00.0 read phy:0x01 reg:0x0f val:0x2000
>>>> kworker/64:2-1028 [064] .... 172.321213: mdio_access: mii-0000:bd:00.0 read phy:0x01 reg:0x00 val:0x1040
>>>> kworker/64:2-1028 [064] .... 172.343209: mdio_access: mii-0000:bd:00.1 read phy:0x03 reg:0x02 val:0x001c
>>>> kworker/64:2-1028 [064] .... 172.343245: mdio_access: mii-0000:bd:00.1 read phy:0x03 reg:0x03 val:0xc916
>>>> kworker/64:2-1028 [064] .... 172.343882: mdio_access: mii-0000:bd:00.1 read phy:0x03 reg:0x01 val:0x79ad
>>>> kworker/64:2-1028 [064] .... 172.343918: mdio_access: mii-0000:bd:00.1 read phy:0x03 reg:0x0f val:0x2000
>>>> kworker/64:2-1028 [064] .... 172.362658: mdio_access: mii-0000:bd:00.1 read phy:0x03 reg:0x00 val:0x1040
>>>> kworker/64:2-1028 [064] .... 172.385961: mdio_access: mii-0000:bd:00.2 read phy:0x05 reg:0x02 val:0x001c
>>>> kworker/64:2-1028 [064] .... 172.385996: mdio_access: mii-0000:bd:00.2 read phy:0x05 reg:0x03 val:0xc916
>>>> kworker/64:2-1028 [064] .... 172.386646: mdio_access: mii-0000:bd:00.2 read phy:0x05 reg:0x01 val:0x79ad
>>>> kworker/64:2-1028 [064] .... 172.386681: mdio_access: mii-0000:bd:00.2 read phy:0x05 reg:0x0f val:0x2000
>>>> kworker/64:2-1028 [064] .... 172.411286: mdio_access: mii-0000:bd:00.2 read phy:0x05 reg:0x00 val:0x1040
>>>> kworker/64:2-1028 [064] .... 172.433225: mdio_access: mii-0000:bd:00.3 read phy:0x07 reg:0x02 val:0x001c
>>>> kworker/64:2-1028 [064] .... 172.433260: mdio_access: mii-0000:bd:00.3 read phy:0x07 reg:0x03 val:0xc916
>>>> kworker/64:2-1028 [064] .... 172.433887: mdio_access: mii-0000:bd:00.3 read phy:0x07 reg:0x01 val:0x79ad
>>>> kworker/64:2-1028 [064] .... 172.433922: mdio_access: mii-0000:bd:00.3 read phy:0x07 reg:0x0f val:0x2000
>>>> kworker/64:2-1028 [064] .... 172.452862: mdio_access: mii-0000:bd:00.3 read phy:0x07 reg:0x00 val:0x1040
>>>> ifconfig-1324 [011] .... 177.325585: mdio_access: mii-0000:bd:00.1 read phy:0x03 reg:0x00 val:0x1040
>>>> kworker/u257:0-8 [012] .... 177.325642: mdio_access: mii-0000:bd:00.1 read phy:0x03 reg:0x04 val:0x01e1
>>>> kworker/u257:0-8 [012] .... 177.325654: mdio_access: mii-0000:bd:00.1 write phy:0x03 reg:0x04 val:0x05e1
>>>> kworker/u257:0-8 [012] .... 177.325708: mdio_access: mii-0000:bd:00.1 read phy:0x03 reg:0x01 val:0x79ad
>>>> kworker/u257:0-8 [012] .... 177.325744: mdio_access: mii-0000:bd:00.1 read phy:0x03 reg:0x09 val:0x0200
>>>> kworker/u257:0-8 [012] .... 177.325779: mdio_access: mii-0000:bd:00.1 read phy:0x03 reg:0x00 val:0x1040
>>>> kworker/u257:0-8 [012] .... 177.325788: mdio_access: mii-0000:bd:00.1 write phy:0x03 reg:0x00 val:0x1240
>>>> kworker/u257:0-8 [012] .... 177.325843: mdio_access: mii-0000:bd:00.1 read phy:0x03 reg:0x01 val:0x798d
>>>
>>> What I think that happens here:
>>> Writing 0x1240 to BMCR starts aneg. When reading BMSR immediately after that then the PHY seems to have cleared
>>> the "aneg complete" bit already, but not yet the "link up" bit. This results in the false "link up" notification.
>>> The following patch is based on the fact that in case of enabled aneg we can't have a valid link if aneg isn't
>>> finished. Could you please test whether this works for you?
>>>
>>> diff --git a/drivers/net/phy/phy_device.c b/drivers/net/phy/phy_device.c
>>> index 6b5cb87f3..7ddd91df9 100644
>>> --- a/drivers/net/phy/phy_device.c
>>> +++ b/drivers/net/phy/phy_device.c
>>> @@ -1774,6 +1774,12 @@ int genphy_update_link(struct phy_device *phydev)
>>> phydev->link = status & BMSR_LSTATUS ? 1 : 0;
>>> phydev->autoneg_complete = status & BMSR_ANEGCOMPLETE ? 1 : 0;
>>>
>>> + /* Consider the case that autoneg was started and "aneg complete"
>>> + * bit has been reset, but "link up" bit not yet.
>>> + */
>>> + if (phydev->autoneg == AUTONEG_ENABLE && !phydev->autoneg_complete)
>>> + phydev->link = 0;
>>> +
>>> return 0;
>>> }
>>> EXPORT_SYMBOL(genphy_update_link);
>>>
>>
>> This patch can solve the issue! Will it be upstream?
>>
> I'll check for side effects, but in general: yes.
>
>> So it's nothing to do with the bios, and just the PHY's own behavior,
>> the "link up" bit can not reset immediately,right?
>>
> Yes, it's the PHY's own behavior, and to a certain extent it may depend on speed
> of the MDIO bus. At least few network chips require a delay of several microseconds
> after each MDIO bus access. This may be sufficient for the PHY to reset the
> link-up bit in time.
>
>> ps: It will take 1 second more to make the link up for RTL8211F when 0x798d happend.
>>
> In polling mode link-up is detected up to 1s after it happened.
> You could switch to interrupt mode to reduce the aneg time.
>
>>
>>
> Heiner
>
> .
>
Thanks very much!
prev parent reply other threads:[~2019-07-31 5:58 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-26 9:53 [RFC] net: phy: read link status twice when phy_check_link_status() Yonglong Liu
2019-07-26 18:14 ` Heiner Kallweit
2019-07-29 3:59 ` liuyonglong
2019-07-29 20:57 ` Heiner Kallweit
2019-07-30 4:03 ` liuyonglong
2019-07-30 6:08 ` Heiner Kallweit
2019-07-30 6:35 ` liuyonglong
2019-07-30 6:39 ` liuyonglong
2019-07-30 19:04 ` Heiner Kallweit
2019-07-31 3:33 ` liuyonglong
2019-07-31 5:44 ` Heiner Kallweit
2019-07-31 5:58 ` liuyonglong [this message]
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=9dd4fe9f-5ee5-23a6-14bf-a5d644567d27@huawei.com \
--to=liuyonglong@huawei.com \
--cc=andrew@lunn.ch \
--cc=davem@davemloft.net \
--cc=hkallweit1@gmail.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linuxarm@huawei.com \
--cc=netdev@vger.kernel.org \
--cc=salil.mehta@huawei.com \
--cc=shiju.jose@huawei.com \
--cc=yisen.zhuang@huawei.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).