Re: lan78xx and phy_state_machine

From: Daniel Wagner <dwagner@suse•de>
To: Russell King - ARM Linux admin <linux@armlinux•org.uk>
Cc: bcm-kernel-feedback-list@broadcom•com,
	linux-rpi-kernel@lists•infradead.org,
	linux-arm-kernel@lists•infradead.org
Subject: Re: lan78xx and phy_state_machine
Date: Mon, 14 Oct 2019 21:25:29 +0200	[thread overview]
Message-ID: <20191014192529.z7c5x6hzixxeplvw@beryllium.lan> (raw)
In-Reply-To: <20191014163004.GP25745@shell.armlinux.org.uk>

On Mon, Oct 14, 2019 at 05:30:04PM +0100, Russell King - ARM Linux admin wrote:
> On Mon, Oct 14, 2019 at 04:06:04PM +0200, Daniel Wagner wrote:
> > Hi,
> > 
> > I've trying to boot a RPi 3 Model B+ in 64 bit mode. While I can get
> > my configuratin booting with v5.2.20, the current kernel v5.3.6 hangs
> > when initializing the eth interface.
> > 
> > Is this a know issue? Some configuration issues?
> 
> I don't see any successfully probed ethernet devices in the boot log, so
> I've no idea which of the multitude of ethernet drivers to look at.  I
> thought maybe I could look at the DT, but I've no idea where
> "arm/bcm2837-rpi-3-b-plus.dts" is located, included by
> arch/arm64/boot/dts/broadcom/bcm2837-rpi-3-b-plus.dts.

Sorry about being so terse. I thought, the RPi devices are well known. My bad.
Anyway, the kernel reports that is the lan78xx driver.

ls -1 /sys/class/net/ | grep -v lo | xargs -n1 -I{} bash -c 'echo -n {} :" " ; basename `readlink -f /sys/class/net/{}/device/driver`'
eth0 : lan78xx

> The oops is because the PHY state machine has been started, but there
> is no phydev->adjust_link set.  Can't say much more than that without
> knowing what the driver is doing.

This was a good tip! After a few printks I figured out what is happening.

phy_connect_direct()
   phy_attach_direct()
     workqueue
       phy_check_link_status()
         phy_link_change


Moving the phy_prepare_link() up in phy_connect_direct() ensures that
phydev->adjust_link is set when the phy_check_link_status() is called.

diff --git a/drivers/net/phy/phy_device.c
b/drivers/net/phy/phy_device.c index 9d2bbb13293e..2a61812bcb0d 100644
--- a/drivers/net/phy/phy_device.c +++ b/drivers/net/phy/phy_device.c
@@ -951,11 +951,12 @@ int phy_connect_direct(struct net_device *dev,
struct phy_device *phydev, if (!dev) return -EINVAL;
 
+       phy_prepare_link(phydev, handler);
+
        rc = phy_attach_direct(dev, phydev, phydev->dev_flags, interface);
        if (rc)
                return rc;
 
-       phy_prepare_link(phydev, handler);
        if (phy_interrupt_is_valid(phydev))
                phy_request_interrupt(phydev);

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