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Subject: Re: [PATCH v2] of: property: fw_devlink: Add support for
 "phy-handle" property
To:     Saravana Kannan <saravanak@google.com>
Cc:     Rob Herring <robh+dt@kernel.org>,
        Frank Rowand <frowand.list@gmail.com>,
        Andrew Lunn <andrew@lunn.ch>, netdev@vger.kernel.org,
        kernel-team@android.com, devicetree@vger.kernel.org,
        linux-kernel@vger.kernel.org,
        Neil Armstrong <narmstrong@baylibre.com>,
        linux-amlogic@lists.infradead.org
From:   Marek Szyprowski <m.szyprowski@samsung.com>
Message-ID: <2023d07e-18bb-e129-760a-18b17ff772cd@samsung.com>
Date:   Wed, 1 Sep 2021 09:22:11 +0200
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Hi Saravana,

On 01.09.2021 04:37, Saravana Kannan wrote:
> On Tue, Aug 24, 2021 at 12:31 AM Saravana Kannan <saravanak@google.com> wrote:
>> On Tue, Aug 24, 2021 at 12:03 AM Marek Szyprowski
>> <m.szyprowski@samsung.com> wrote:
>>> On 23.08.2021 20:22, Saravana Kannan wrote:
>>>> On Mon, Aug 23, 2021 at 5:08 AM Marek Szyprowski
>>>> <m.szyprowski@samsung.com> wrote:
>>>>> On 18.08.2021 04:17, Saravana Kannan wrote:
>>>>>> Allows tracking dependencies between Ethernet PHYs and their consumers.
>>>>>>
>>>>>> Cc: Andrew Lunn <andrew@lunn.ch>
>>>>>> Cc: netdev@vger.kernel.org
>>>>>> Signed-off-by: Saravana Kannan <saravanak@google.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@ff600000/mdio-multiplexer@4c000
>>> 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.

I've just checked it and it doesn't help in my case. 
ff64c000.mdio-multiplexer and ff3f0000.ethernet are still not probed 
after applying this patch.

> 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.

I'm waiting for the proper fix then.

Best regards

-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland