Hi,
I have observed that carrier_changes is one even in case of the ethernet
link is up.
After investigating the code below is my observation –
ethernet_driver_probe()
+--->phy_connect()
| +--->phy_attach_direct()
| +---> netif_carrier_off() : which increments
carrier_changes to one.
+--->register_netdevice() : will the carrier_changes becomes zero here ?
+--->netif_carrier_off(): not increment the carrier_changes since
__LINK_STATE_NOCARRIER already set.
From ethernet driver open will start the PHY and trigger the
phy_state_machine.
Phy_state_machine workqueue calling netif_carrier_on() once the link is UP.
netif_carrier_on() increments the carrier_changes by one.
If the call trace is correct, then there is at least two problems here:
- phy_connect() does start the PHY machine which means that as soon as
it detects a link state of any kind (up or down) it can call
netif_carrier_off() respectively netif_carrier_on()
- as soon as you call register_netdevice() notifiers run and other parts
of the kernel or user-space programs can see an inconsistent link state
I would suggest doing the following sequence instead:
netif_carrier_off()
register_netdevice()
phy_connect()
Which should result in a consistent link state and carrier value.
After link is UP if we check the carrier_changes sysfs node - it will be
one only.
$ cat /sys/class/net/eth0/carrier_changes
1
After reverting the change - https://lkml.org/lkml/2016/1/9/173 (net:
phy: turn carrier off on phy attach) then I could see the carrier
changes incremented to 2 after Link UP.
$ cat /sys/class/net/eth0/carrier_changes
2
Thanks,
Bhadram.
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Thanks for responding.
-----Original Message-----
From: Florian Fainelli [mailto:f.fainelli@gmail.com]
Sent: Friday, September 01, 2017 5:53 AM
To: Bhadram Varka <redacted>; andrew@lunn.ch
Cc: linux-netdev <redacted>
Subject: Re: netdev carrier changes is one even after ethernet link up.
On 08/30/2017 10:53 PM, Bhadram Varka wrote:
Hi,
I have observed that carrier_changes is one even in case of the
ethernet link is up.
After investigating the code below is my observation –
ethernet_driver_probe()
+--->phy_connect()
| +--->phy_attach_direct()
| +---> netif_carrier_off() : which increments
carrier_changes to one.
+--->register_netdevice() : will the carrier_changes becomes zero here ?
+--->netif_carrier_off(): not increment the carrier_changes since
__LINK_STATE_NOCARRIER already set.
From ethernet driver open will start the PHY and trigger the
phy_state_machine.
Phy_state_machine workqueue calling netif_carrier_on() once the link is UP.
netif_carrier_on() increments the carrier_changes by one.
If the call trace is correct, then there is at least two problems here:
- phy_connect() does start the PHY machine which means that as soon as it detects a link state of any kind (up or down) it can call
netif_carrier_off() respectively netif_carrier_on()
- as soon as you call register_netdevice() notifiers run and other parts of the kernel or user-space programs can see an inconsistent link state
I would suggest doing the following sequence instead:
netif_carrier_off()
register_netdevice()
phy_connect()
Which should result in a consistent link state and carrier value.
Yes, It will address the issue.
If we did the phy_conect in ndo_open it will make the carrier changes as one. But if we did in probe function then it's not working.
In ethernet driver probe - (below sequence is not working)
phy_connect()
register_netdevice()
netif_carrier_off()
working sequence:
In probe():
register_netdevice()
ndo_open:
phy_connect()
Thanks,
Bhadram.
After link is UP if we check the carrier_changes sysfs node - it will
be one only.
$ cat /sys/class/net/eth0/carrier_changes
1
After reverting the change - https://lkml.org/lkml/2016/1/9/173 (net:
phy: turn carrier off on phy attach) then I could see the carrier
changes incremented to 2 after Link UP.
$ cat /sys/class/net/eth0/carrier_changes
2
Thanks,
Bhadram.
----------------------------------------------------------------------
-- This email message is for the sole use of the intended recipient(s)
and may contain confidential information. Any unauthorized review,
use, disclosure or distribution is prohibited. If you are not the
intended recipient, please contact the sender by reply email and
destroy all copies of the original message.
----------------------------------------------------------------------
--
-----Original Message-----
From: Florian Fainelli [mailto:f.fainelli@gmail.com]
Sent: Friday, September 01, 2017 5:53 AM
To: Bhadram Varka <redacted>; andrew@lunn.ch
Cc: linux-netdev <redacted>
Subject: Re: netdev carrier changes is one even after ethernet link up.
On 08/30/2017 10:53 PM, Bhadram Varka wrote:
quoted
Hi,
I have observed that carrier_changes is one even in case of the
ethernet link is up.
After investigating the code below is my observation –
ethernet_driver_probe()
+--->phy_connect()
| +--->phy_attach_direct()
| +---> netif_carrier_off() : which increments
carrier_changes to one.
+--->register_netdevice() : will the carrier_changes becomes zero here ?
+--->netif_carrier_off(): not increment the carrier_changes since
__LINK_STATE_NOCARRIER already set.
From ethernet driver open will start the PHY and trigger the
phy_state_machine.
Phy_state_machine workqueue calling netif_carrier_on() once the link is
UP.
quoted
netif_carrier_on() increments the carrier_changes by one.
If the call trace is correct, then there is at least two problems here:
- phy_connect() does start the PHY machine which means that as soon as it
detects a link state of any kind (up or down) it can call
netif_carrier_off() respectively netif_carrier_on()
- as soon as you call register_netdevice() notifiers run and other parts of the
kernel or user-space programs can see an inconsistent link state
I would suggest doing the following sequence instead:
netif_carrier_off()
register_netdevice()
phy_connect()
Which should result in a consistent link state and carrier value.
Yes, It will address the issue.
If we did the phy_conect in ndo_open it will make the carrier changes as two. But if we did in probe function then it's not working.
In ethernet driver probe - (below sequence is not working)
phy_connect()
register_netdevice()
netif_carrier_off()
working sequence:
In probe():
register_netdevice()
ndo_open:
phy_connect()
After reverting - https://lkml.org/lkml/2016/1/9/173 this works if we do phy_connect in probe as well.
Thanks,
Bhadram.
quoted
After link is UP if we check the carrier_changes sysfs node - it will
be one only.
$ cat /sys/class/net/eth0/carrier_changes
1
After reverting the change - https://lkml.org/lkml/2016/1/9/173 (net:
phy: turn carrier off on phy attach) then I could see the carrier
changes incremented to 2 after Link UP.
$ cat /sys/class/net/eth0/carrier_changes
2
Thanks,
Bhadram.
----------------------------------------------------------------------
-- This email message is for the sole use of the intended recipient(s)
and may contain confidential information. Any unauthorized review,
use, disclosure or distribution is prohibited. If you are not the
intended recipient, please contact the sender by reply email and
destroy all copies of the original message.
----------------------------------------------------------------------
--
-----Original Message-----
From: Florian Fainelli [mailto:f.fainelli@gmail.com]
Sent: Friday, September 01, 2017 5:53 AM
To: Bhadram Varka <redacted>; andrew@lunn.ch
Cc: linux-netdev <redacted>
Subject: Re: netdev carrier changes is one even after ethernet link up.
On 08/30/2017 10:53 PM, Bhadram Varka wrote:
quoted
Hi,
I have observed that carrier_changes is one even in case of the
ethernet link is up.
After investigating the code below is my observation –
ethernet_driver_probe()
+--->phy_connect()
| +--->phy_attach_direct()
| +---> netif_carrier_off() : which increments
carrier_changes to one.
+--->register_netdevice() : will the carrier_changes becomes zero here ?
+--->netif_carrier_off(): not increment the carrier_changes since
__LINK_STATE_NOCARRIER already set.
From ethernet driver open will start the PHY and trigger the
phy_state_machine.
Phy_state_machine workqueue calling netif_carrier_on() once the link is
UP.
quoted
netif_carrier_on() increments the carrier_changes by one.
If the call trace is correct, then there is at least two problems here:
- phy_connect() does start the PHY machine which means that as soon as it
detects a link state of any kind (up or down) it can call
netif_carrier_off() respectively netif_carrier_on()
- as soon as you call register_netdevice() notifiers run and other parts of the
kernel or user-space programs can see an inconsistent link state
I would suggest doing the following sequence instead:
netif_carrier_off()
register_netdevice()
phy_connect()
Which should result in a consistent link state and carrier value.
Yes, It will address the issue.
If we did the phy_conect in ndo_open it will make the carrier changes as two. But if we did in probe function then it's not working.
In ethernet driver probe - (below sequence is not working)
phy_connect()
register_netdevice()
netif_carrier_off()
working sequence:
In probe():
register_netdevice()
ndo_open:
phy_connect()
After reverting - https://lkml.org/lkml/2016/1/9/173 this works if we do phy_connect in probe as well.
But as mentioned before you should not be doing the PHY probe in your
driver's probe function for different reasons:
- the probe function's responsibility is to initialize the driver and
the HW to a state where they both have everything needed but it should
be in quiesced state. There is no guarantee that your network device may
ever be used after probe unless something calls ndo_open(), you should
therefore keep all resources to a minimum: memory allocated, HW powered
down etc.
- there is a race condition between the PHY state machine started in
phy_connect(), and when register_netdevice() is called and notifiers
running which can lead to an inconsistent state for the carrier
So considering that your driver does not do that, I am not sure what you
are expecting...
--
Florian
-----Original Message-----
From: Florian Fainelli [mailto:f.fainelli@gmail.com]
Sent: Saturday, September 02, 2017 7:25 AM
To: Bhadram Varka <redacted>; andrew@lunn.ch
Cc: linux-netdev <redacted>
Subject: Re: netdev carrier changes is one even after ethernet link up.
On 08/31/2017 10:49 PM, Bhadram Varka wrote:
quoted
Thanks for responding. Now responding inline
quoted
-----Original Message-----
From: Florian Fainelli [mailto:f.fainelli@gmail.com]
Sent: Friday, September 01, 2017 5:53 AM
To: Bhadram Varka <redacted>; andrew@lunn.ch
Cc: linux-netdev <redacted>
Subject: Re: netdev carrier changes is one even after ethernet link up.
On 08/30/2017 10:53 PM, Bhadram Varka wrote:
quoted
Hi,
I have observed that carrier_changes is one even in case of the
ethernet link is up.
After investigating the code below is my observation -
ethernet_driver_probe()
+--->phy_connect()
| +--->phy_attach_direct()
| +---> netif_carrier_off() : which increments
carrier_changes to one.
+--->register_netdevice() : will the carrier_changes becomes zero here ?
+--->netif_carrier_off(): not increment the carrier_changes since
__LINK_STATE_NOCARRIER already set.
From ethernet driver open will start the PHY and trigger the
phy_state_machine.
Phy_state_machine workqueue calling netif_carrier_on() once the link
is
UP.
quoted
netif_carrier_on() increments the carrier_changes by one.
If the call trace is correct, then there is at least two problems here:
- phy_connect() does start the PHY machine which means that as soon
as it detects a link state of any kind (up or down) it can call
netif_carrier_off() respectively netif_carrier_on()
- as soon as you call register_netdevice() notifiers run and other
parts of the kernel or user-space programs can see an inconsistent
link state
I would suggest doing the following sequence instead:
netif_carrier_off()
register_netdevice()
phy_connect()
Which should result in a consistent link state and carrier value.
Yes, It will address the issue.
If we did the phy_conect in ndo_open it will make the carrier changes as
two. But if we did in probe function then it's not working.
quoted
In ethernet driver probe - (below sequence is not working)
phy_connect()
register_netdevice()
netif_carrier_off()
working sequence:
In probe():
register_netdevice()
ndo_open:
phy_connect()
After reverting - https://lkml.org/lkml/2016/1/9/173 this works if we do
phy_connect in probe as well.
But as mentioned before you should not be doing the PHY probe in your
driver's probe function for different reasons:
- the probe function's responsibility is to initialize the driver and the HW to a
state where they both have everything needed but it should be in quiesced
state. There is no guarantee that your network device may ever be used
after probe unless something calls ndo_open(), you should therefore keep
all resources to a minimum: memory allocated, HW powered down etc.
- there is a race condition between the PHY state machine started in
phy_connect(), and when register_netdevice() is called and notifiers running
which can lead to an inconsistent state for the carrier
Agreed. But I could see lot of drivers performing the phy_connect() in driver_probe() function itself.
Also observed that these drivers are performing netif_carrier_off() after register_netdevice().
My point is that we do we need to do netif_carrier_off() in phy_connect since we already doing the same after register_netdevice() ?
Thanks!
-----------------------------------------------------------------------------------
This email message is for the sole use of the intended recipient(s) and may contain
confidential information. Any unauthorized review, use, disclosure or distribution
is prohibited. If you are not the intended recipient, please contact the sender by
reply email and destroy all copies of the original message.
-----------------------------------------------------------------------------------
-----Original Message-----
From: Florian Fainelli [mailto:f.fainelli@gmail.com]
Sent: Saturday, September 02, 2017 7:25 AM
To: Bhadram Varka <redacted>; andrew@lunn.ch
Cc: linux-netdev <redacted>
Subject: Re: netdev carrier changes is one even after ethernet link up.
On 08/31/2017 10:49 PM, Bhadram Varka wrote:
quoted
Thanks for responding. Now responding inline
quoted
-----Original Message-----
From: Florian Fainelli [mailto:f.fainelli@gmail.com]
Sent: Friday, September 01, 2017 5:53 AM
To: Bhadram Varka <redacted>; andrew@lunn.ch
Cc: linux-netdev <redacted>
Subject: Re: netdev carrier changes is one even after ethernet link up.
On 08/30/2017 10:53 PM, Bhadram Varka wrote:
quoted
Hi,
I have observed that carrier_changes is one even in case of the
ethernet link is up.
After investigating the code below is my observation -
ethernet_driver_probe()
+--->phy_connect()
| +--->phy_attach_direct()
| +---> netif_carrier_off() : which increments
carrier_changes to one.
+--->register_netdevice() : will the carrier_changes becomes zero here ?
+--->netif_carrier_off(): not increment the carrier_changes since
__LINK_STATE_NOCARRIER already set.
From ethernet driver open will start the PHY and trigger the
phy_state_machine.
Phy_state_machine workqueue calling netif_carrier_on() once the link
is
UP.
quoted
netif_carrier_on() increments the carrier_changes by one.
If the call trace is correct, then there is at least two problems here:
- phy_connect() does start the PHY machine which means that as soon
as it detects a link state of any kind (up or down) it can call
netif_carrier_off() respectively netif_carrier_on()
- as soon as you call register_netdevice() notifiers run and other
parts of the kernel or user-space programs can see an inconsistent
link state
I would suggest doing the following sequence instead:
netif_carrier_off()
register_netdevice()
phy_connect()
Which should result in a consistent link state and carrier value.
Yes, It will address the issue.
If we did the phy_conect in ndo_open it will make the carrier changes as
two. But if we did in probe function then it's not working.
quoted
In ethernet driver probe - (below sequence is not working)
phy_connect()
register_netdevice()
netif_carrier_off()
working sequence:
In probe():
register_netdevice()
ndo_open:
phy_connect()
After reverting - https://lkml.org/lkml/2016/1/9/173 this works if we do
phy_connect in probe as well.
But as mentioned before you should not be doing the PHY probe in your
driver's probe function for different reasons:
- the probe function's responsibility is to initialize the driver and the HW to a
state where they both have everything needed but it should be in quiesced
state. There is no guarantee that your network device may ever be used
after probe unless something calls ndo_open(), you should therefore keep
all resources to a minimum: memory allocated, HW powered down etc.
- there is a race condition between the PHY state machine started in
phy_connect(), and when register_netdevice() is called and notifiers running
which can lead to an inconsistent state for the carrier
Agreed. But I could see lot of drivers performing the phy_connect() in driver_probe() function itself.
Also observed that these drivers are performing netif_carrier_off() after register_netdevice().
My point is that why do we need to do netif_carrier_off() in phy_connect() since we already doing the same after register_netdevice() in MAC driver ?
Thanks!
-----------------------------------------------------------------------------------
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confidential information. Any unauthorized review, use, disclosure or distribution
is prohibited. If you are not the intended recipient, please contact the sender by
reply email and destroy all copies of the original message.
-----------------------------------------------------------------------------------