netdev - Re: [PATCH 2/4] ravb: Add optional PHY reset during system resume

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Message-ID: <47456e34-2c2f-ec19-fcda-e3132a8037b3@cogentembedded.com>
Date:   Sat, 30 Sep 2017 23:23:42 +0300
From:   Sergei Shtylyov <sergei.shtylyov@...entembedded.com>
To:     Florian Fainelli <f.fainelli@...il.com>,
        Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:     Geert Uytterhoeven <geert+renesas@...der.be>,
        "David S . Miller" <davem@...emloft.net>,
        Simon Horman <horms@...ge.net.au>,
        Magnus Damm <magnus.damm@...il.com>,
        Andrew Lunn <andrew@...n.ch>,
        Niklas Söderlund 
        <niklas.soderlund+renesas@...natech.se>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        Linux-Renesas <linux-renesas-soc@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>
Subject: Re: [PATCH 2/4] ravb: Add optional PHY reset during system resume

Hello!

On 09/28/2017 10:21 PM, Florian Fainelli wrote:

>>>> If the optional "reset-gpios" property is specified in DT, the generic
>>>> MDIO bus code takes care of resetting the PHY during device probe.
>>>> However, the PHY may still have to be reset explicitly after system
>>>> resume.
>>>>
>>>> This allows to restore Ethernet operation after resume from s2ram on
>>>> Salvator-XS, where the enable pin of the regulator providing PHY power
>>>> is connected to PRESETn, and PSCI suspend powers down the SoC.
>>>>
>>>> Signed-off-by: Geert Uytterhoeven <geert+renesas@...der.be>
>>>> ---
>>>>   drivers/net/ethernet/renesas/ravb_main.c | 9 +++++++++
>>>>   1 file changed, 9 insertions(+)
>>>>
>>>> diff --git a/drivers/net/ethernet/renesas/ravb_main.c b/drivers/net/ethernet/renesas/ravb_main.c
>>>> index fdf30bfa403bf416..96d1d48e302f8c9a 100644
>>>> --- a/drivers/net/ethernet/renesas/ravb_main.c
>>>> +++ b/drivers/net/ethernet/renesas/ravb_main.c
[...]
>>>> @@ -2302,6 +2304,13 @@ static int __maybe_unused ravb_resume(struct device *dev)
>>>>         * reopen device if it was running before system suspended.
>>>>         */
>>>>
>>>> +     /* PHY reset */
>>>> +     if (bus->reset_gpiod) {
>>>> +             gpiod_set_value_cansleep(bus->reset_gpiod, 1);
>>>> +             udelay(bus->reset_delay_us);
>>>> +             gpiod_set_value_cansleep(bus->reset_gpiod, 0);
>>>> +     }
>>>
>>> This is a clever hack, but unfortunately this is also misusing the MDIO
>>> bus reset line into a PHY reset line. As commented in patch 3, if this
>>> reset line is tied to the PHY, then this should be a PHY property and
>>
>> OK.
>>
>>> you cannot (ab)use the MDIO bus GPIO reset logic anymore...
>>
>> And then I should add reset-gpios support to drivers/net/phy/micrel.c?
>> Or is there already generic code to handle per-PHY reset? I couldn't find it.
> 
> There is not such a thing unfortunately, but it would presumably be

    It's strange you don't remember about my (abandoned) patches to handle 
per=PHY reset GPIOs -- perhaps it's time to unearth them. Here they are:

http://patchwork.ozlabs.org/patch/616495/
http://patchwork.ozlabs.org/patch/616501/

    I had v3 in the works before abandoning this series -- it doesn't apply now.

> called within drivers/net/phy/mdio_bus.c during bus->reset() time
> because you need the PHY reset to be deasserted before you can
> successfully read/write from the PHY, and if you can't read/write from
> the PHY, the MDIO bus layer cannot read the PHY ID, and therefore cannot
> match a PHY device with its driver, so things don't work.

    I did this a bit differently...

[...]

MBR, Sergei