netdev - Re: regression?: ti: cpsw: warning from phy_connect()->sysfs_create_link()-sysfs_warn

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Message-ID: <2679eb4c-b08a-4ef7-a6e8-de7425a47e94@gmail.com>
Date:   Mon, 26 Feb 2018 12:16:53 -0800
From:   Florian Fainelli <f.fainelli@...il.com>
To:     Grygorii Strashko <grygorii.strashko@...com>,
        netdev@...r.kernel.org, Andrew Lunn <andrew@...n.ch>
Cc:     David Miller <davem@...emloft.net>, Sekhar Nori <nsekhar@...com>
Subject: Re: regression?: ti: cpsw: warning from
 phy_connect()->sysfs_create_link()-sysfs_warn_dup()

On 02/26/2018 12:08 PM, Grygorii Strashko wrote:
> 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 #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:
> 
> 5568363f0cb3 ("net: phy: Create sysfs reciprocal links for attached_dev/phydev"
> a3995460491d ("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.

The CPSW driver is duplicating a fair amount of what the DSA subsystem
does properly without breaking any assumptions about the 1:1 mapping
that can exist between a network device and PHY device. Having a PHY
device without a network device is fine in premise, although discouraged.

Migrating to DSA is certainly a big task, but I would strongly encourage
you to consider doing it, since that would solve this problem, and
probably many more.

> 
> 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.
> 


-- 
Florian