Re: Lockup in phy_probe() for MDIO device (Broadcom's switch)

On 30.09.2021 12:40, Russell King (Oracle) wrote:

In phy_probe, can you add:

	WARN_ON(!(phydev->mdio.flags & MDIO_DEVICE_FLAG_PHY));

just to make sure we have a real PHY device there please? Maybe also
print the value of the flags argument.

MDIO_DEVICE_FLAG_PHY is set by phy_create_device() before the mutex is
initialised, so if it is set, the lock should be initialised.

Maybe also print mdiodev->flags in mdio_device_register() as well, so
we can see what is being registered and the flags being used for that
device.

Could it be that openwrt is carrying a patch that is causing this
issue?

I don't think there is any OpenWrt patch affecting that.

MDIO_DEVICE_FLAG_PHY seems to be missing.

[    5.593833] libphy: Fixed MDIO Bus: probed
[    5.598383] libphy: iProc MDIO bus: probed
[    5.602510] iproc-mdio 18003000.mdio: Broadcom iProc MDIO bus registered
[    5.609918] libphy: mdio_mux: probed
[    5.613533] mdio_bus 0.0:10: flags: 0x00000000
[    5.618816] libphy: mdio_mux: probed
[    5.622440] mdio_bus 0.200:00: flags: 0x00000000
[    5.627479] Broadcom B53 (2) 0.200:00: flags: 0x00000000
[    5.632811] ------------[ cut here ]------------
[    5.637475] WARNING: CPU: 0 PID: 1 at drivers/net/phy/phy_device.c:2828 phy_probe+0x40/0x1d4
[    5.645946] Modules linked in:
[    5.649011] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.10.64 #0
[    5.655030] Hardware name: BCM5301X
[    5.658543] [<c0108410>] (unwind_backtrace) from [<c0104bc4>] (show_stack+0x10/0x14)
[    5.666316] [<c0104bc4>] (show_stack) from [<c03dc6a8>] (dump_stack+0x94/0xa8)
[    5.673565] [<c03dc6a8>] (dump_stack) from [<c01183e8>] (__warn+0xb8/0x114)
[    5.680546] [<c01183e8>] (__warn) from [<c01184ac>] (warn_slowpath_fmt+0x68/0x78)
[    5.688050] [<c01184ac>] (warn_slowpath_fmt) from [<c04b8d78>] (phy_probe+0x40/0x1d4)
[    5.695909] [<c04b8d78>] (phy_probe) from [<c0457120>] (really_probe+0xfc/0x4e0)
[    5.703325] [<c0457120>] (really_probe) from [<c0455378>] (bus_for_each_drv+0x74/0x98)
[    5.711262] [<c0455378>] (bus_for_each_drv) from [<c04576b8>] (__device_attach+0xcc/0x120)
[    5.719548] [<c04576b8>] (__device_attach) from [<c0456300>] (bus_probe_device+0x84/0x8c)
[    5.727747] [<c0456300>] (bus_probe_device) from [<c04529ac>] (device_add+0x300/0x77c)
[    5.735687] [<c04529ac>] (device_add) from [<c04ba3dc>] (mdio_device_register+0x38/0x5c)
[    5.743801] [<c04ba3dc>] (mdio_device_register) from [<c04c1b08>] (of_mdiobus_register+0x198/0x2fc)
[    5.752868] [<c04c1b08>] (of_mdiobus_register) from [<c04c238c>] (mdio_mux_init+0x178/0x2c0)
[    5.761328] [<c04c238c>] (mdio_mux_init) from [<c04c2668>] (mdio_mux_mmioreg_probe+0x138/0x1fc)
[    5.770054] [<c04c2668>] (mdio_mux_mmioreg_probe) from [<c0458ee4>] (platform_drv_probe+0x34/0x70)
[    5.779032] [<c0458ee4>] (platform_drv_probe) from [<c0457120>] (really_probe+0xfc/0x4e0)
[    5.787230] [<c0457120>] (really_probe) from [<c0457b04>] (device_driver_attach+0xe4/0xf4)
[    5.795516] [<c0457b04>] (device_driver_attach) from [<c0457b90>] (__driver_attach+0x7c/0x110)
[    5.804149] [<c0457b90>] (__driver_attach) from [<c04552d8>] (bus_for_each_dev+0x64/0x90)
[    5.812340] [<c04552d8>] (bus_for_each_dev) from [<c04564f8>] (bus_add_driver+0xf8/0x1e0)
[    5.820540] [<c04564f8>] (bus_add_driver) from [<c045819c>] (driver_register+0x88/0x118)
[    5.828652] [<c045819c>] (driver_register) from [<c01017e4>] (do_one_initcall+0x54/0x1e8)
[    5.836863] [<c01017e4>] (do_one_initcall) from [<c0801118>] (kernel_init_freeable+0x23c/0x290)
[    5.845583] [<c0801118>] (kernel_init_freeable) from [<c065ad40>] (kernel_init+0x8/0x118)
[    5.853781] [<c065ad40>] (kernel_init) from [<c0100128>] (ret_from_fork+0x14/0x2c)
[    5.861367] Exception stack(0xc1035fb0 to 0xc1035ff8)
[    5.866425] 5fa0:                                     00000000 00000000 00000000 00000000
[    5.874618] 5fc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
[    5.882816] 5fe0: 00000000 00000000 00000000 00000000 00000013 00000000
[    5.889473] ---[ end trace f28513567c7daf95 ]---
[    5.894105] ------------[ cut here ]------------
[    5.898743] WARNING: CPU: 0 PID: 1 at kernel/locking/mutex.c:951 __mutex_lock.constprop.0+0x744/0x848
[    5.907983] DEBUG_LOCKS_WARN_ON(lock->magic != lock)

diff --git a/drivers/net/phy/mdio_device.c b/drivers/net/phy/mdio_device.c
index 0837319a5..910149c8d 100644
--- a/drivers/net/phy/mdio_device.c
+++ b/drivers/net/phy/mdio_device.c

@@ -83,6 +83,8 @@ int mdio_device_register(struct mdio_device *mdiodev)
        if (err)
                return err;

+       dev_info(&mdiodev->dev, "flags: 0x%08x\n", mdiodev->flags);
+
        err = device_add(&mdiodev->dev);
        if (err) {
                pr_err("MDIO %d failed to add\n", mdiodev->addr);

diff --git a/drivers/net/phy/phy_device.c b/drivers/net/phy/phy_device.c
index 950277e4d..02c06e6d5 100644
--- a/drivers/net/phy/phy_device.c
+++ b/drivers/net/phy/phy_device.c

@@ -2824,6 +2824,9 @@ static int phy_probe(struct device *dev)
        struct phy_driver *phydrv = to_phy_driver(drv);
        int err = 0;

+       dev_info(dev, "flags: 0x%08x\n", phydev->mdio.flags);
+       WARN_ON(!(phydev->mdio.flags & MDIO_DEVICE_FLAG_PHY));
+
        phydev->drv = phydrv;

        /* Disable the interrupt if the PHY doesn't support it