Re: [PATCH] Revert "net: phy: turn carrier off on phy attach"

On February 14, 2016 10:25:30 AM PST, Clemens Gruber [off-list ref] wrote:

On Fri, Feb 12, 2016 at 10:56:04AM -0800, Florian Fainelli wrote:

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On 12/02/16 10:01, Clemens Gruber wrote:

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Commit 113c74d83eef ("net: phy: turn carrier off on phy attach")

breaks

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the eth0 link coming up on all my i.MX6Q boards with a Marvell

88E1510.

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If I then do a ifconfig eth0 down/up cycle I first get a MDIO read
timeout but then the link becomes ready and everything is back to
normal.
Without this step however, the link stays down forever, an

unusually

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high amount of phy interrupts occur (about 10000/second) and

kworker/0:2

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is constantly using over 60% of the CPU.

Reverting it fixes the problems with the link not coming up at boot

as

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well as the high amount of phy interrupts and kworker load in that
state.

You are seeing this with the FEC driver right? We probably want to
carefully audit the driver and understand what could be going wrong,

the

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initial change is correct, so there must be something else going on

here.

I think I found the underlying problem!
It was not the fec driver but the marvell phy driver, more specifically
the marvell_of_reg_init call being made too late, which lead to the
observed problem at half the boot ups where the link never came up.

With the marvell,reg-init device tree parameter, a flag needs to be set
to tell the Marvell 88E1510 that it should enable the interrupt output.
(At a specific pin, in my case LED[2])
If this is not set (or set too late), the phydev->state is set to UP in
phy_start (called from fec_enet_open) but then, the auto-negotiation
never starts.
In comparison, now, after I called marvell_of_reg_init not in
m88e1510_config_aneg but in marvell_probe, everything works again :)
About a second after the fec_enet_open/phy_start calls, the
auto-negotiation starts (m88e1510_config_aneg) and the phy state
changes
from UP to AN, to CHANGELINK and finally to RUNNING.

I will send a patch shortly, calling marvell_of_reg_init from a new
m88e1510_probe function instead of the m88e1510_config_aneg function.

config_init is more appropriate here since this call back will be called even if there is a software reset (e.g: from phy_init_hw). config_aneg is definitely too late, thanks for finding this!

-- 
Florian