linux-kernel - Re: [PATCH net-next 0/2] net: mdio: add amlogic gxl mdio mux support

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Message-ID: <1jr0vqyet1.fsf@starbuckisacylon.baylibre.com>
Date:   Thu, 19 Jan 2023 11:42:11 +0100
From:   Jerome Brunet <jbrunet@...libre.com>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     netdev@...r.kernel.org, "David S. Miller" <davem@...emloft.net>,
        linux-amlogic@...ts.infradead.org,
        Kevin Hilman <khilman@...libre.com>,
        Neil Armstrong <neil.armstrong@...aro.org>,
        Da Xue <da@...sconfused.com>, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next 0/2] net: mdio: add amlogic gxl mdio mux support


On Wed 18 Jan 2023 at 04:08, Andrew Lunn <andrew@...n.ch> wrote:

> On Mon, Jan 16, 2023 at 10:16:34AM +0100, Jerome Brunet wrote:
>> Add support for the MDIO multiplexer found in the Amlogic GXL SoC family.
>> This multiplexer allows to choose between the external (SoC pins) MDIO bus,
>> or the internal one leading to the integrated 10/100M PHY.
>> 
>> This multiplexer has been handled with the mdio-mux-mmioreg generic driver
>> so far. When it was added, it was thought the logic was handled by a
>> single register.
>> 
>> It turns out more than a single register need to be properly set.
>> As long as the device is using the Amlogic vendor bootloader, or upstream
>> u-boot with net support, it is working fine since the kernel is inheriting
>> the bootloader settings. Without net support in the bootloader, this glue
>> comes unset in the kernel and only the external path may operate properly.
>> 
>> With this driver (and the associated DT update), the kernel no longer relies
>> on the bootloader to set things up, fixing the problem.
>
> Ideally, you should also post an actual user of this driver, i.e. the
> DT updates.

I usually avoid doing this since the DT part is intended for another
maintainer. The idea is make life easy for them and let them pick the
entire series (or not). I don't mind sending the DT update along if it
is the perferred way with netdev.

FYI, the DT update would look like this :
https://gitlab.com/jbrunet/linux/-/commit/1d38ccf1b9f264111b1c56f18cfb4804227d3894.patch

>
>> This has been tested on the aml-s905x-cc (LePotato) for the internal path
>> and the aml-s912-pc (Tartiflette) for the external path.
>
> So these exist in mainline, which is enough for me.

Yes the boards exists in mainline, there are still using the mdio-mux-mmioreg driver
ATM

>
>    Andrew