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

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Date:   Wed, 28 Nov 2018 01:17:10 +0000
From:   Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>
To:     Heiner Kallweit <hkallweit1@...il.com>,
        Andrew Lunn <andrew@...n.ch>
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

Hi Heiner,

> From: Heiner Kallwei, Sent: Wednesday, November 28, 2018 4:46 AM
> 
> 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?

Thank you for your comment!
As Geert mentioned on this email thread, that patch can handle if user opened
the NIC and then the PHY was active.

>  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().

I should have mentioned on the commit log, but phy_scan_fixups() is called
by phy_init_hw() and phy_init_hw() is called phy_attach_direct(). So,
I think we can remove phy_scan_fixups(). However, as you mentioned,
this patch could have side effects...

So, I'll make such a suspend/resume patch that Andrew mentioned later.

Best regards,
Yoshihiro Shimoda