linux-kernel - Re: [PATCH 2/2] net: fec: Create device link between phy dev and mac dev

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Message-ID: <6dca5756-cee2-6921-d5d0-2d36a6023355@windriver.com>
Date:   Thu, 17 Nov 2022 12:40:03 +0800
From:   "Wang, Xiaolei" <xiaolei.wang@...driver.com>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     hkallweit1@...il.com, linux@...linux.org.uk, davem@...emloft.net,
        edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] net: fec: Create device link between phy dev and mac
 dev


On 11/16/2022 11:07 PM, Andrew Lunn wrote:
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>
> On Wed, Nov 16, 2022 at 10:43:05PM +0800, Xiaolei Wang wrote:
>> On imx6sx, there are two fec interfaces, but the external
>> phys can only be configured by fec0 mii_bus. That means
>> the fec1 can't work independently, it only work when the
>> fec0 is active. It is alright in the normal boot since the
>> fec0 will be probed first. But then the fec0 maybe moved
>> behind of fec1 in the dpm_list due to various device link.
>> So in system suspend and resume, we would get the following
>> warning when configuring the external phy of fec1 via the
>> fec0 mii_bus due to the inactive of fec0. In order to fix
>> this issue, we create a device link between phy dev and fec0.
>> This will make sure that fec0 is always active when fec1
>> is in active mode.
>>
>>    WARNING: CPU: 0 PID: 24 at drivers/net/phy/phy.c:983 phy_error+0x20/0x68
>>    Modules linked in:
>>    CPU: 0 PID: 24 Comm: kworker/0:2 Not tainted 6.1.0-rc3-00011-g5aaef24b5c6d-dirty #34
>>    Hardware name: Freescale i.MX6 SoloX (Device Tree)
>>    Workqueue: events_power_efficient phy_state_machine
>>    unwind_backtrace from show_stack+0x10/0x14
>>    show_stack from dump_stack_lvl+0x68/0x90
>>    dump_stack_lvl from __warn+0xb4/0x24c
>>    __warn from warn_slowpath_fmt+0x5c/0xd8
>>    warn_slowpath_fmt from phy_error+0x20/0x68
>>    phy_error from phy_state_machine+0x22c/0x23c
>>    phy_state_machine from process_one_work+0x288/0x744
>>    process_one_work from worker_thread+0x3c/0x500
>>    worker_thread from kthread+0xf0/0x114
>>    kthread from ret_from_fork+0x14/0x28
>>    Exception stack(0xf0951fb0 to 0xf0951ff8)
> Please add an explanation why you only do this for the FEC? Is this
> not a problem for any board which has the PHY on an MDIO bus not
> direct child of the MAC?

Hi

Oh, my initial idea is to provide such an interface, we can add links 
manually in such cases, if it is to solve this type of problem, my idea 
is to create a link in phy_connect_direct, or is there any better 
suggestion?

thanks

xiaolei

>
>         Andrew