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

From: Jerome Brunet <jbrunet@baylibre.com>
To: Andrew Lunn <andrew@lunn.ch>
Cc: netdev@vger.kernel.org, "David S. Miller" <davem@davemloft.net>,
	linux-amlogic@lists.infradead.org,
	Kevin Hilman <khilman@baylibre.com>,
	Neil Armstrong <neil.armstrong@linaro.org>,
	Da Xue <da@lessconfused.com>,
	devicetree@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH net-next 0/2] net: mdio: add amlogic gxl mdio mux support
Date: Thu, 19 Jan 2023 11:42:11 +0100	[thread overview]
Message-ID: <1jr0vqyet1.fsf@starbuckisacylon.baylibre.com> (raw)
In-Reply-To: <Y8dimCI7ybeL09j0@lunn.ch>

On Wed 18 Jan 2023 at 04:08, Andrew Lunn <andrew@lunn.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