netdev - Re: [PATCH/RFC] net: phy: device: Don't deassert the reset when register and probe

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Date:   Tue, 27 Nov 2018 20:45:49 +0100
From:   Heiner Kallweit <hkallweit1@...il.com>
To:     Andrew Lunn <andrew@...n.ch>,
        Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>
Cc:     "f.fainelli@...il.com" <f.fainelli@...il.com>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-renesas-soc@...r.kernel.org" 
        <linux-renesas-soc@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>
Subject: Re: [PATCH/RFC] net: phy: device: Don't deassert the reset when
 register and probe

On 27.11.2018 17:44, Andrew Lunn wrote:
> On Tue, Nov 27, 2018 at 12:18:20PM +0000, Yoshihiro Shimoda wrote:
>> Some PHY device needs edge signal of the reset, but the previous code
>> is impossible to achieve it like following:
>>
>>  1) Kernel boots by using initramfs.
>>  --> No open the nic, so the provious code deasserts the reset by
>>      phy_device_register() and phy_probe().
>>  2) Kernel enters the suspend.
>>  --> So, keep the reset signal as deassert.
>>  --> On R-Car Salvator-XS board, unfortunately, the board power is
>>      turned off.
>>  3) Kernel returns from suspend.
>>  4) ifconfig eth0 up
>>  --> Then, since edge signal of the reset doesn't happen,
>>      it cannot link up.
> 
> Hi Yoshihiro
> 
> It sounds like you should be adding code to the suspend/resume
> handling of phylib, so that it toggle the reset on resume. You cannot
> just delete code like you proposed, it is going to break devices. But
> adding code should be O.K.
> 
The commit message mentions that the patch is supposed to fix some
issue on the Salvator-XS board. I found the following from a year ago
https://www.spinics.net/lists/netdev/msg457308.html
which is also about PHY reset and this board. Is there still something
open?  But as Andrew mentioned already: Just deleting code w/o
checking what it's good for and whether this could have side effects,
isn't a solution. Especially because the patch would silently remove
the call to phy_scan_fixups().

Heiner

>        Andrew
> .
>