linux-kernel - Re: [PATCH NET V5 2/2] net: hns: Use phy

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Message-ID: <20170628202819.GA22815@lunn.ch>
Date:   Wed, 28 Jun 2017 22:28:19 +0200
From:   Andrew Lunn <andrew@...n.ch>
To:     Yunsheng Lin <linyunsheng@...wei.com>
Cc:     davem@...emloft.net, f.fainelli@...il.com,
        huangdaode@...ilicon.com, xuwei5@...ilicon.com,
        liguozhu@...ilicon.com, Yisen.Zhuang@...wei.com,
        gabriele.paoloni@...wei.com, john.garry@...wei.com,
        linuxarm@...wei.com, salil.mehta@...wei.com, lipeng321@...wei.com,
        tremyfr@...il.com, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH NET V5 2/2] net: hns: Use phy_driver to setup Phy loopback

> >>From your description, it sounds like you can call phy_resume() on a
> > device which is not suspended. 
> Do you mean after calling dev_close, the device is still not suspended?

You only call dev_close() if the device is running. What if somebody
runs the self test on an interface when it has never been opened? It
looks like you will call phy_resume(). But since it has never been
suspended, you could be in trouble.
> 
> In general, suspend is expected to
> > store away state which will be lost when powering down a
> > device. Resume writes that state back into the device after it is
> > powered up. So resuming a device which was never suspended could write
> > bad state into it.
>
> Do you mean phydev->suspended has bad state?

phy_resume() current does not check the phydev->suspended state.

> > Also, what about if WOL has been set before closing the device?
>
> phy_suspend will return errro.
> 
> int phy_suspend(struct phy_device *phydev)
> {
> 	struct phy_driver *phydrv = to_phy_driver(phydev->mdio.dev.driver);
> 	struct ethtool_wolinfo wol = { .cmd = ETHTOOL_GWOL };
> 	int ret = 0;
> 
> 	/* If the device has WOL enabled, we cannot suspend the PHY */
> 	phy_ethtool_get_wol(phydev, &wol);
> 	if (wol.wolopts)
> 		return -EBUSY;
> 
> 	if (phydev->drv && phydrv->suspend)
> 		ret = phydrv->suspend(phydev);
> 
> 	if (ret)
> 		return ret;
> 
> 	phydev->suspended = true;
> 
> 	return ret;
> }

Which means when you call phy_resume() in lb_setup() you are again
resuming a device which is not suspended...

	 Andrew