linux-kernel - Re: [PATCH] mdio_bus: suppress err message for reset gpio EPROBE

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Message-ID: <7c2e8a07-4cb6-ee9c-9d64-9cf68b0390c7@gmail.com>
Date:   Thu, 19 Nov 2020 17:58:56 +0100
From:   Heiner Kallweit <hkallweit1@...il.com>
To:     Grygorii Strashko <grygorii.strashko@...com>,
        "David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
        Jakub Kicinski <kuba@...nel.org>, Andrew Lunn <andrew@...n.ch>
Cc:     linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mdio_bus: suppress err message for reset gpio
 EPROBE_DEFER

Am 19.11.2020 um 14:38 schrieb Grygorii Strashko:
> 
> 
> On 19/11/2020 14:30, Heiner Kallweit wrote:
>> Am 18.11.2020 um 15:24 schrieb Grygorii Strashko:
>>> The mdio_bus may have dependencies from GPIO controller and so got
>>> deferred. Now it will print error message every time -EPROBE_DEFER is
>>> returned from:
>>> __mdiobus_register()
>>>   |-devm_gpiod_get_optional()
>>> without actually identifying error code.
>>>
>>> "mdio_bus 4a101000.mdio: mii_bus 4a101000.mdio couldn't get reset GPIO"
>>>
>>> Hence, suppress error message when devm_gpiod_get_optional() returning
>>> -EPROBE_DEFER case.
>>>
>>> Signed-off-by: Grygorii Strashko <grygorii.strashko@...com>
>>> ---
>>>   drivers/net/phy/mdio_bus.c | 7 ++++---
>>>   1 file changed, 4 insertions(+), 3 deletions(-)
>>>
>>> diff --git a/drivers/net/phy/mdio_bus.c b/drivers/net/phy/mdio_bus.c
>>> index 757e950fb745..54fc13043656 100644
>>> --- a/drivers/net/phy/mdio_bus.c
>>> +++ b/drivers/net/phy/mdio_bus.c
>>> @@ -546,10 +546,11 @@ int __mdiobus_register(struct mii_bus *bus, struct module *owner)
>>>       /* de-assert bus level PHY GPIO reset */
>>>       gpiod = devm_gpiod_get_optional(&bus->dev, "reset", GPIOD_OUT_LOW);
>>>       if (IS_ERR(gpiod)) {
>>> -        dev_err(&bus->dev, "mii_bus %s couldn't get reset GPIO\n",
>>> -            bus->id);
>>> +        err = PTR_ERR(gpiod);
>>> +        if (err != -EPROBE_DEFER)
>>> +            dev_err(&bus->dev, "mii_bus %s couldn't get reset GPIO %d\n", bus->id, err);
>>>           device_del(&bus->dev);
>>> -        return PTR_ERR(gpiod);
>>> +        return err;
>>>       } else    if (gpiod) {
>>>           bus->reset_gpiod = gpiod;
>>>  
>>
>> Using dev_err_probe() here would simplify the code.
>>
> 
> this was my first though, but was not sure if it's correct as dev_err_probe() will use dev
> to store defer reason, but the same 'dev' is deleted on the next line.
> 
If you look at device_del() you see that it calls driver_deferred_probe_del()
which frees the reason string. Means you're right in a way that storing
the deferral reason doesn't provide any benefit here, but it also doesn't
hurt.
Good thing about using dev_err_probe() is also that it prints a debug info
in case of deferral what may help people chasing an issue involving this
deferral.

> I also thought about using bus->parent, but it's not always provided.
> 
> So, if you think dev_err_probe(0) can be used - I can change and re-send.
>