netdev - Re: Potential issue with f5e64032a799 "net: phy: fix resume handling"

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Message-ID: <80586c54-2a59-04ef-a623-78d340ba6206@gmail.com>
Date:   Sun, 25 Feb 2018 14:00:43 +0100
From:   Heiner Kallweit <hkallweit1@...il.com>
To:     Andrew Lunn <andrew@...n.ch>,
        Russell King <rmk+kernel@...linux.org.uk>
Cc:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: Potential issue with f5e64032a799 "net: phy: fix resume handling"

Am 03.02.2018 um 21:17 schrieb Andrew Lunn:
> On Sat, Feb 03, 2018 at 05:41:54PM +0100, Heiner Kallweit wrote:
>> This commit forces callers of phy_resume() and phy_suspend() to hold
>> mutex phydev->lock. This was done for calls to phy_resume() and
>> phy_suspend() in phylib, however there are more callers in network
>> drivers. I'd assume that these other calls issue a warning now
>> because of the lock not being held.
>> So is there something I miss or would this have to be fixed?
> 
> Hi Heiner
> 
> This is a good point.
> 
> Yes, it looks like some fixes are needed. But what exactly?
> 
The issue with phy_suspend/phy_resume and the changed locking
behavior is still open AFAICS. There was a proposed fix
https://www.mail-archive.com/netdev@vger.kernel.org/msg215455.html
and then the discussion stopped.
I think we need the fix before 4.16 leaves the rc phase.

Heiner


> The phy state machine will suspend and resume the phy is you call
> phy_stop() and phy_start() in the MAC suspend and resume functions.
> 
> A few examples:
> 
> tc35815_suspend(), ravb_suspend() via ravb_close(), sh_eth_suspend()
> via sh_eth_close(), fec_suspend(), mpc52xx_fec_of_suspend() via
> mpc52xx_fec_close(), ucc_geth_suspend(), etc...
> 
> So i suspect those drivers which call phy_suspend()/phy_resume()
> should really be modified to call phy_stop()/phy_start().
> 
> hns_nic_config_phy_loopback() is just funky, and probably needs the
> help of the hns guys to fix.
> 
> dsa_slave_suspend() already does a phy_stop(), so the phy_suspend()
> can be removed.
> 
> The comments in lpc_eth_open() suggest the phy_resume() is needed, so
> locks should be added. socfpga_dwmac_resume() seems to be the same.
> 
>     Andrew
>