linux-kernel - Re: [PATCH 4.4 17/86] phy: micrel: Disable auto negotiation on startup

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Date:   Tue, 19 May 2020 08:45:12 +0300
From:   Henri Rosten <henri.rosten@...kie.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        Alexandre Belloni <alexandre.belloni@...e-electrons.com>,
        "David S. Miller" <davem@...emloft.net>,
        Sasha Levin <sashal@...nel.org>, lukas.bulwahn@...il.com
Subject: Re: [PATCH 4.4 17/86] phy: micrel: Disable auto negotiation on
 startup

On Mon, May 18, 2020 at 07:35:48PM +0200, Greg Kroah-Hartman wrote:
> From: Alexandre Belloni <alexandre.belloni@...e-electrons.com>
> 
> [ Upstream commit 99f81afc139c6edd14d77a91ee91685a414a1c66 ]

I notice 99f81afc139c has been reverted in mainline with commit b43bd72835a5.  
The revert commit points out that:

"It was papering over the real problem, which is fixed by commit
f555f34fdc58 ("net: phy: fix auto-negotiation stall due to unavailable
interrupt")"
 
Therefore, consider backporting f555f34fdc58 instead of 99f81afc139c.

Notice if f555f34fdc58 is taken, then I believe 215d08a85b9a should also 
be backported.

Thanks,
-- Henri

> 
> Disable auto negotiation on init to properly detect an already plugged
> cable at boot.
> 
> At boot, when the phy is started, it is in the PHY_UP state.
> However, if a cable is plugged at boot, because auto negociation is already
> enabled at the time we get the first interrupt, the phy is already running.
> But the state machine then switches from PHY_UP to PHY_AN and calls
> phy_start_aneg(). phy_start_aneg() will not do anything because aneg is
> already enabled on the phy. It will then wait for a interrupt before going
> further. This interrupt will never happen unless the cable is unplugged and
> then replugged.
> 
> It was working properly before 321beec5047a (net: phy: Use interrupts when
> available in NOLINK state) because switching to NOLINK meant starting
> polling the phy, even if IRQ were enabled.
>