linux-kernel - Re: [PATCH net-next v1 1/1] net: usb: asix: ax88772: suspend PHY on driver probe

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Date:   Fri, 2 Jul 2021 05:53:40 +0200
From:   Oleksij Rempel <o.rempel@...gutronix.de>
To:     Florian Fainelli <f.fainelli@...il.com>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>, Andrew Lunn <andrew@...n.ch>,
        Heiner Kallweit <hkallweit1@...il.com>,
        Russell King <linux@...linux.org.uk>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        kernel@...gutronix.de, linux-kernel@...r.kernel.org,
        linux-usb@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [PATCH net-next v1 1/1] net: usb: asix: ax88772: suspend PHY on
 driver probe

On Thu, Jul 01, 2021 at 12:01:04PM -0700, Florian Fainelli wrote:
> On 6/28/21 9:43 PM, Oleksij Rempel wrote:
> > After probe/bind sequence is the PHY in active state, even if interface
> > is stopped. As result, on some systems like Samsung Exynos5250 SoC based Arndale
> > board, the ASIX PHY will be able to negotiate the link but fail to
> > transmit the data.
> > 
> > To handle it, suspend the PHY on probe.
> 
> Very unusual, could not the PHY be attached/connected to a ndo_open()
> time like what most drivers do?

May be this can be done to.
But, should not the PHY be in the same state after phy_connect() and after
phy_stop()?

Currently, phy_connect() and phy_start() resume the PHY. The phy_stop()
is suspending it. Since the driver calls phy_connect(), phy_start() and
phy_stop(), the resume/suspend state is out of balance.
In case some one will add for example something like regulator_enable/disable
callbacks in to phydev->syspend/resume callbacks, this would never work.

So, the question is, should phy_connect() put the PHY back in to suspend
mode? Or should the MAC driver take care of this?

> > 
> > Fixes: e532a096be0e ("net: usb: asix: ax88772: add phylib support")
> > Signed-off-by: Oleksij Rempel <o.rempel@...gutronix.de>
> > Reported-by: Marek Szyprowski <m.szyprowski@...sung.com>
> > Tested-by: Marek Szyprowski <m.szyprowski@...sung.com>
> > ---
> >  drivers/net/usb/asix_devices.c | 1 +
> >  1 file changed, 1 insertion(+)
> > 
> > diff --git a/drivers/net/usb/asix_devices.c b/drivers/net/usb/asix_devices.c
> > index aec97b021a73..2c115216420a 100644
> > --- a/drivers/net/usb/asix_devices.c
> > +++ b/drivers/net/usb/asix_devices.c
> > @@ -701,6 +701,7 @@ static int ax88772_init_phy(struct usbnet *dev)
> >  		return ret;
> >  	}
> >  
> > +	phy_suspend(priv->phydev);
> >  	priv->phydev->mac_managed_pm = 1;
> >  
> >  	phy_attached_info(priv->phydev);
> > 
> 
> 
> -- 
> Florian
> 

Regards,
Oleksij
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