regression?: ti: cpsw: warning from phy_connect()->sysfs_create_link(…

…)-sysfs_warn_dup()

Hi Florian,

The TI CPSW driver produces warning as below when booted in switch mode:
[    8.882295] sysfs: cannot create duplicate filename '/devices/platform/44000000.ocp/48484000.ethernet/net/eth0/phydev'
[    8.999859] CPU: 1 PID: 356 Comm: systemd-network Not tainted 4.16.0-rc3-00010-g6cc3ff6-dirty torvalds#225
...
[    9.012352] Hardware name: Generic DRA74X (Flattened Device Tree)
[    9.018901] Backtrace:
[    9.021376] [<c010c918>] (dump_backtrace) from [<c010cbe8>] (show_stack+0x18/0x1c)
[    9.028986]  r7:ed036240 r6:60070013 r5:00000000 r4:c0d598a0
[    9.034684] [<c010cbd0>] (show_stack) from [<c088e1f0>] (dump_stack+0x8c/0xa0)
[    9.041954] [<c088e164>] (dump_stack) from [<c02ba59c>] (sysfs_warn_dup+0x60/0x6c)
[    9.049564]  r7:ed036240 r6:ed036240 r5:c0b579bc r4:ed10c000
[    9.055264] [<c02ba53c>] (sysfs_warn_dup) from [<c02ba930>] (sysfs_do_create_link_sd+0xbc/0xc4)
[    9.064006]  r7:ed036240 r6:ffffffef r5:00000000 r4:ed034660
[    9.069701] [<c02ba874>] (sysfs_do_create_link_sd) from [<c02ba968>] (sysfs_create_link+0x30/0x3c)
[    9.078706]  r9:00000008 r8:00000000 r7:ed02f008 r6:ee015ae8 r5:ee015800 r4:ed02f000
[    9.086497] [<c02ba938>] (sysfs_create_link) from [<c060f070>] (phy_attach_direct+0x180/0x1f4)
[    9.095163] [<c060eef0>] (phy_attach_direct) from [<c060f1cc>] (phy_connect_direct+0x1c/0x54)
[    9.103735]  r10:00000001 r9:ee015d0c r8:00000008 r7:c062e84c r6:c062e84c r5:ed02f000
[    9.111609]  r4:ed02f000 r3:00000008
[    9.115217] [<c060f1b0>] (phy_connect_direct) from [<c060f250>] (phy_connect+0x4c/0x80)
[    9.123270]  r7:c062e84c r6:ee015800 r5:ed02f000 r4:ee693664
[    9.128969] [<c060f204>] (phy_connect) from [<c062abc8>] (cpsw_slave_open+0x21c/0x274)
[    9.136926]  r9:ee015d0c r8:ee015d00 r7:ed018a10 r6:ee015800 r5:ee015d00 r4:ed032630
[    9.144715] [<c062a9ac>] (cpsw_slave_open) from [<c062b28c>] (cpsw_ndo_open+0x158/0x55c)
[    9.152860]  r10:00000001 r9:00000000 r8:ee015d00 r7:c0d04c48 r6:ee015800 r5:ed018a10
[    9.160730]  r4:ed032630
[    9.163291] [<c062b134>] (cpsw_ndo_open) from [<c0765350>] (__dev_open+0xd4/0x158)
[    9.170900]  r10:00000000 r9:ec885db4 r8:ee01582c r7:c09a9c00 r6:00000000 r5:c0d04c48
[    9.178768]  r4:ee015800
[    9.181326] [<c076527c>] (__dev_open) from [<c0765748>] (__dev_change_flags+0x174/0x1c0)

The reason of the warning is that in switch mode CPSW drivers is connecting two Net PHYs to
a single network device (it has been done this way when driver was initially introduced), so
now it produces warning during boot because of commits:

5568363 ("net: phy: Create sysfs reciprocal links for attached_dev/phydev"
a399546 ("net: phy: Relax error checking on sysfs_create_link()"
^ both went in v4.13

Honestly, I'm not sure how to fix it the best way (the simplest fix is below), taking into account
that we are not ready to do big reworks in CPSW driver.

Sry, for the late report - in LKML most of dual port TI platforms configured to work in
dual mac mode, therefore two network devices are created and warning not displayed.

--
regards,
-grygorii
------
From ef2e612652cb7afa844993b23156315f0df7d24f Mon Sep 17 00:00:00 2001
From: Grygorii Strashko <grygorii.strashko@ti.com>
Date: Mon, 26 Feb 2018 13:53:28 -0600
Subject: [PATCH] [RFC] net: phy: suppress warning when >1 phys connected to one netdev

Some ethernet drivers (like TI CPSW) may connect and manage >1 Net PHYs per
one netdevice, as result such drivers will produce warning during system
boot: 'sysfs: cannot create duplicate filename
'/devices/platform/44000000.ocp/48484000.ethernet/net/eth0/phydev''.

The code introduced waring was added by commit 5568363 ("net: phy:
Create sysfs reciprocal links for attached_dev/phydev").

Fix above, by using sysfs_create_link_nowarn() when "phydev" link from
netdev->phydev is created in phy_attach_direct()

Signed-off-by: Grygorii Strashko <grygorii.strashko@ti.com>

drivers/net/phy/phy_device.c

@@ -1014,8 +1014,9 @@ int phy_attach_direct(struct net_device *dev, struct phy_device *phydev,
 	err = sysfs_create_link(&phydev->mdio.dev.kobj, &dev->dev.kobj,
 				"attached_dev");
 	if (!err) {
-		err = sysfs_create_link(&dev->dev.kobj, &phydev->mdio.dev.kobj,
-					"phydev");
+		err = sysfs_create_link_nowarn(&dev->dev.kobj,
+					       &phydev->mdio.dev.kobj,
+					       "phydev");
 		if (err)
 			goto error;