From: Florian Fainelli <f.fainelli@gmail.com>
To: Antoine Tenart <antoine.tenart@bootlin.com>,
Andrew Lunn <andrew@lunn.ch>
Cc: davem@davemloft.net, linux@armlinux.org.uk, hkallweit1@gmail.com,
netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
thomas.petazzoni@bootlin.com, maxime.chevallier@bootlin.com,
gregory.clement@bootlin.com, miquel.raynal@bootlin.com,
nadavh@marvell.com, stefanc@marvell.com, mw@semihalf.com
Subject: Re: [PATCH net-next v2 3/3] net: phy: marvell10g: set the PHY in low power by default
Date: Fri, 1 Mar 2019 19:08:56 -0800 [thread overview]
Message-ID: <d17bdf0c-f1b8-99e3-b199-a99a7f7347d3@gmail.com> (raw)
In-Reply-To: <20190301150706.GD3554@kwain>
On 3/1/2019 7:07 AM, Antoine Tenart wrote:
> Hi Andrew,
>
> On Fri, Mar 01, 2019 at 03:19:53PM +0100, Andrew Lunn wrote:
>> On Fri, Mar 01, 2019 at 12:00:47PM +0100, Antoine Tenart wrote:
>>> When the Marvell 10G PHYs are set out of reset, the LPOWER bit is set
>>> depending on an hardware configuration choice. We also do not know what
>>> is the PHY state at boot time. Hence, set the PHY in low power by
>>> default when this driver probes.
>>
>> Florian did some work for c22 PHYs so that the existing link state
>> could be used at boot. So for example, the bootloader configured the
>> PHY up and it got link, there is no need to down/up the PHY when linux
>> takes control. The networking comes up faster that way.
>>
>> Can this work for this PHY?
>
> This use case (the bootloader configures the PHY, Linux boots and sets
> an interface using this PHY up) would work, and is what's happening in
> some situations right now (the 3310 reset is never asserted prior to
> this series).
>
> But consider this case (let's say we use a 10G link):
>
> ---------------- ----------------
> | Board 1 | | Board 2 |
> | MAC — 3310 — | — SFP cable — | — 3310 — MAC |
> ---------------- ----------------
>
> Board 1: The userspace do not set the interface up. The MAC is in reset
> (default state during the MAC driver probe), the PHY was
> configured by the bootloader.
> Board 2: The userspace set the interface up. The MAC is configured, the
> PHY is configured as well.
>
> The two PHY's PCS will establish a link and report it as being up. In
> this case, phylink's AN mode is MLO_AN_PHY and thus will report the
> overall link as being the PHY's link status: up.
>
> My understanding is that the issue arises because the PHYs were never
> set in reset, or low power, and thus act as if the user wanted the port
> to be up. As the default behaviour for networking ports is to be down at
> boot, I thought to set the PHY as well in a default low power state.
The policy you are creating here for the marvell10g driver is entirely
applicable to any PHY <=> PHY configuration where either of the two
software agents on Board 1 or Board 2 has not had a chance to bring-up
its bootloader/OS/applications to control the PHY.
A number of PHYs come up fully on (or in isolate or super isolate mode)
and will AN with their link partner if connected. For some people it's a
feature, for some it is a waste of power. I don't necessarily have an
issue with your patch per-se, but it does create an one off behavior
that other PHY drivers may not follow.
--
Florian
next prev parent reply other threads:[~2019-03-02 3:09 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-03-01 11:00 [PATCH net-next v2 0/3] net: phy: marvell10g: implement suspend/resume callbacks Antoine Tenart
2019-03-01 11:00 ` [PATCH net-next v2 1/3] " Antoine Tenart
2019-03-01 14:16 ` Andrew Lunn
2019-03-01 11:00 ` [PATCH net-next v2 2/3] net: phy: marvell10g: add the suspend/resume callbacks for the 88x2210 Antoine Tenart
2019-03-01 14:15 ` Andrew Lunn
2019-03-01 11:00 ` [PATCH net-next v2 3/3] net: phy: marvell10g: set the PHY in low power by default Antoine Tenart
2019-03-01 14:19 ` Andrew Lunn
2019-03-01 15:07 ` Antoine Tenart
2019-03-02 3:08 ` Florian Fainelli [this message]
2019-03-04 10:47 ` Antoine Tenart
2019-03-04 16:10 ` Russell King - ARM Linux admin
2019-03-05 12:54 ` Antoine Tenart
2019-03-04 18:46 ` [PATCH net-next v2 0/3] net: phy: marvell10g: implement suspend/resume callbacks David Miller
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