netdev - Re: [PATCH v2] of: property: fw_devlink: Add support for "phy-handle" property

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Date:   Tue, 31 Aug 2021 19:37:09 -0700
From:   Saravana Kannan <saravanak@...gle.com>
To:     Marek Szyprowski <m.szyprowski@...sung.com>
Cc:     Rob Herring <robh+dt@...nel.org>,
        Frank Rowand <frowand.list@...il.com>,
        Andrew Lunn <andrew@...n.ch>, netdev@...r.kernel.org,
        kernel-team@...roid.com, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Neil Armstrong <narmstrong@...libre.com>,
        linux-amlogic@...ts.infradead.org
Subject: Re: [PATCH v2] of: property: fw_devlink: Add support for "phy-handle" property

On Tue, Aug 24, 2021 at 12:31 AM Saravana Kannan <saravanak@...gle.com> wrote:
>
> On Tue, Aug 24, 2021 at 12:03 AM Marek Szyprowski
> <m.szyprowski@...sung.com> wrote:
> >
> > Hi,
> >
> > On 23.08.2021 20:22, Saravana Kannan wrote:
> > > On Mon, Aug 23, 2021 at 5:08 AM Marek Szyprowski
> > > <m.szyprowski@...sung.com> wrote:
> > >> On 18.08.2021 04:17, Saravana Kannan wrote:
> > >>> Allows tracking dependencies between Ethernet PHYs and their consumers.
> > >>>
> > >>> Cc: Andrew Lunn <andrew@...n.ch>
> > >>> Cc: netdev@...r.kernel.org
> > >>> Signed-off-by: Saravana Kannan <saravanak@...gle.com>
> > >> This patch landed recently in linux-next as commit cf4b94c8530d ("of:
> > >> property: fw_devlink: Add support for "phy-handle" property"). It breaks
> > >> ethernet operation on my Amlogic-based ARM64 boards: Odroid C4
> > >> (arm64/boot/dts/amlogic/meson-sm1-odroid-c4.dts) and N2
> > >> (meson-g12b-odroid-n2.dts) as well as Khadas VIM3/VIM3l
> > >> (meson-g12b-a311d-khadas-vim3.dts and meson-sm1-khadas-vim3l.dts).
> > >>
> > >> In case of OdroidC4 I see the following entries in the
> > >> /sys/kernel/debug/devices_deferred:
> > >>
> > >> ff64c000.mdio-multiplexer
> > >> ff3f0000.ethernet
> > >>
> > >> Let me know if there is anything I can check to help debugging this issue.
> > > I'm fairly certain you are hitting this issue because the PHY device
> > > doesn't have a compatible property. And so the device link dependency
> > > is propagated up to the mdio bus. But busses as suppliers aren't good
> > > because busses never "probe".
> > >
> > > PHY seems to be one of those cases where it's okay to have the
> > > compatible property but also okay to not have it. You can confirm my
> > > theory by checking for the list of suppliers under
> > > ff64c000.mdio-multiplexer. You'd see mdio@0 (ext_mdio) and if you look
> > > at the "status" file under the folder it should be "dormant". If you
> > > add a compatible property that fits the formats a PHY node can have,
> > > that should also fix your issue (not the solution though).
> >
> > Where should I look for the mentioned device links 'status' file?
> >
> > # find /sys -name ff64c000.mdio-multiplexer
> > /sys/devices/platform/soc/ff600000.bus/ff64c000.mdio-multiplexer
> > /sys/bus/platform/devices/ff64c000.mdio-multiplexer
> >
> > # ls -l /sys/devices/platform/soc/ff600000.bus/ff64c000.mdio-multiplexer
> > total 0
>
> This is the folder I wanted you to check.
>
> > lrwxrwxrwx 1 root root    0 Jan  1 00:04
> > consumer:platform:ff3f0000.ethernet ->
> > ../../../../virtual/devlink/platform:ff64c000.mdio-multiplexer--platform:ff3f0000.ethernet
>
> But I should have asked to look for the consumer list and not the
> supplier list. In any case, we can see that the ethernet is marked as
> the consumer of the mdio-multiplexer instead of the PHY device. So my
> hunch seems to be right.
>
> > -rw-r--r-- 1 root root 4096 Jan  1 00:04 driver_override
> > -r--r--r-- 1 root root 4096 Jan  1 00:04 modalias
> > lrwxrwxrwx 1 root root    0 Jan  1 00:04 of_node ->
> > ../../../../../firmware/devicetree/base/soc/bus@...00000/mdio-multiplexer@...00
> > drwxr-xr-x 2 root root    0 Jan  1 00:02 power
> > lrwxrwxrwx 1 root root    0 Jan  1 00:04 subsystem ->
> > ../../../../../bus/platform
> > lrwxrwxrwx 1 root root    0 Jan  1 00:04
> > supplier:platform:ff63c000.system-controller:clock-controller ->
> > ../../../../virtual/devlink/platform:ff63c000.system-controller:clock-controller--platform:ff64c000.mdio-multiplexer
> > -rw-r--r-- 1 root root 4096 Jan  1 00:04 uevent
> > -r--r--r-- 1 root root 4096 Jan  1 00:04 waiting_for_supplier
> >
> > # cat
> > /sys/devices/platform/soc/ff600000.bus/ff64c000.mdio-multiplexer/waiting_for_supplier
> > 0
> >
> > I'm also not sure what compatible string should I add there.
>
> It should have been added to external_phy: ethernet-phy@0. But don't
> worry about it (because you need to use a specific format for the
> compatible string).
>

Marek,

Can you give this a shot?
https://lore.kernel.org/lkml/20210831224510.703253-1-saravanak@google.com/

This is not the main fix for the case you brought up, but it should
fix your issue as a side effect of fixing another issue.

The main fix for your issue would be to teach fw_devlink that
phy-handle always points to the actual DT node that'll become a device
even if it doesn't have a compatible property. I'll send that out
later.

-Saravana