netdev - Re: [PATCH net] net: phy: rtl8211f: do a double read to get real time link status

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Date:   Thu, 8 Aug 2019 08:11:33 +0200
From:   Heiner Kallweit <hkallweit1@...il.com>
To:     Yonglong Liu <liuyonglong@...wei.com>, davem@...emloft.net,
        andrew@...n.ch
Cc:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        linuxarm@...wei.com, salil.mehta@...wei.com,
        yisen.zhuang@...wei.com, shiju.jose@...wei.com
Subject: Re: [PATCH net] net: phy: rtl8211f: do a double read to get real time
 link status

On 08.08.2019 03:15, Yonglong Liu wrote:
> 
> 
> On 2019/8/8 0:47, Heiner Kallweit wrote:
>> On 07.08.2019 15:16, Yonglong Liu wrote:
>>> [   27.232781] hns3 0000:bd:00.3 eth7: net open
>>> [   27.237303] 8021q: adding VLAN 0 to HW filter on device eth7
>>> [   27.242972] IPv6: ADDRCONF(NETDEV_CHANGE): eth7: link becomes ready
>>> [   27.244449] hns3 0000:bd:00.3: invalid speed (-1)
>>> [   27.253904] hns3 0000:bd:00.3 eth7: failed to adjust link.
>>> [   27.259379] RTL8211F Gigabit Ethernet mii-0000:bd:00.3:07: PHY state change UP -> RUNNING
>>> [   27.924903] hns3 0000:bd:00.3 eth7: link up
>>> [   28.280479] RTL8211F Gigabit Ethernet mii-0000:bd:00.3:07: PHY state change RUNNING -> NOLINK
>>> [   29.208452] hns3 0000:bd:00.3 eth7: link down
>>> [   32.376745] RTL8211F Gigabit Ethernet mii-0000:bd:00.3:07: PHY state change NOLINK -> RUNNING
>>> [   33.208448] hns3 0000:bd:00.3 eth7: link up
>>> [   35.253821] hns3 0000:bd:00.3 eth7: net stop
>>> [   35.258270] hns3 0000:bd:00.3 eth7: link down
>>>
>>> When using rtl8211f in polling mode, may get a invalid speed,
>>> because of reading a fake link up and autoneg complete status
>>> immediately after starting autoneg:
>>>
>>>         ifconfig-1176  [007] ....    27.232763: mdio_access: mii-0000:bd:00.3 read  phy:0x07 reg:0x00 val:0x1040
>>>   kworker/u257:1-670   [015] ....    27.232805: mdio_access: mii-0000:bd:00.3 read  phy:0x07 reg:0x04 val:0x01e1
>>>   kworker/u257:1-670   [015] ....    27.232815: mdio_access: mii-0000:bd:00.3 write phy:0x07 reg:0x04 val:0x05e1
>>>   kworker/u257:1-670   [015] ....    27.232869: mdio_access: mii-0000:bd:00.3 read  phy:0x07 reg:0x01 val:0x79ad
>>>   kworker/u257:1-670   [015] ....    27.232904: mdio_access: mii-0000:bd:00.3 read  phy:0x07 reg:0x09 val:0x0200
>>>   kworker/u257:1-670   [015] ....    27.232940: mdio_access: mii-0000:bd:00.3 read  phy:0x07 reg:0x00 val:0x1040
>>>   kworker/u257:1-670   [015] ....    27.232949: mdio_access: mii-0000:bd:00.3 write phy:0x07 reg:0x00 val:0x1240
>>>   kworker/u257:1-670   [015] ....    27.233003: mdio_access: mii-0000:bd:00.3 read  phy:0x07 reg:0x01 val:0x79ad
>>>   kworker/u257:1-670   [015] ....    27.233039: mdio_access: mii-0000:bd:00.3 read  phy:0x07 reg:0x0a val:0x3002
>>>   kworker/u257:1-670   [015] ....    27.233074: mdio_access: mii-0000:bd:00.3 read  phy:0x07 reg:0x09 val:0x0200
>>>   kworker/u257:1-670   [015] ....    27.233110: mdio_access: mii-0000:bd:00.3 read  phy:0x07 reg:0x05 val:0x0000
>>>   kworker/u257:1-670   [000] ....    28.280475: mdio_access: mii-0000:bd:00.3 read  phy:0x07 reg:0x01 val:0x7989
>>>   kworker/u257:1-670   [000] ....    29.304471: mdio_access: mii-0000:bd:00.3 read  phy:0x07 reg:0x01 val:0x7989
>>>
>>> According to the datasheet of rtl8211f, to get the real time
>>> link status, need to read MII_BMSR twice.
>>>
>>> This patch add a read_status hook for rtl8211f, and do a fake
>>> phy_read before genphy_read_status(), so that can get real link
>>> status in genphy_read_status().
>>>
>>> Signed-off-by: Yonglong Liu <liuyonglong@...wei.com>
>>> ---
>>>  drivers/net/phy/realtek.c | 13 +++++++++++++
>>>  1 file changed, 13 insertions(+)
>>>
>> Is this an accidental resubmit? Because we discussed this in
>> https://marc.info/?t=156413509900003&r=1&w=2 and a fix has
>> been applied already.
>>
>> Heiner
>>
>> .
>>
> 
> In https://marc.info/?t=156413509900003&r=1&w=2 , the invalid speed
> recurrence rate is almost 100%, and I had test the solution about
> 5 times and it works. But yesterday it happen again suddenly, and than
> I fount that the recurrence rate reduce to 10%. This time we get 0x79ad
> after autoneg started which is not 0x798d from last discussion.
> 
> 
> 
OK, I'll have a look.
However the approach is wrong. The double read is related to the latching
of link-down events. This is done by all PHY's and not specific to RT8211F.
Also it's not related to the problem. I assume any sufficient delay would
do instead of the read.