netdev - Re: [PATCH net-next 6/6] net: mvpp2: Consider NVMEM cells as possible MAC address source

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Message-ID: <CAPv3WKdZ+tsW-jRJt_n=KqT+oEe+5QAEFOWKrXsTjHCBBzEh0A@mail.gmail.com>
Date:   Sat, 19 Nov 2022 09:18:34 +0100
From:   Marcin Wojtas <mw@...ihalf.com>
To:     Miquel Raynal <miquel.raynal@...tlin.com>
Cc:     Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        devicetree@...r.kernel.org,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Eric Dumazet <edumazet@...gle.com>, netdev@...r.kernel.org,
        Russell King <linux@...linux.org.uk>,
        Taras Chornyi <tchornyi@...vell.com>,
        linux-kernel@...r.kernel.org,
        Robert Marko <robert.marko@...tura.hr>,
        Luka Perkov <luka.perkov@...tura.hr>,
        Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
        Michael Walle <michael@...le.cc>
Subject: Re: [PATCH net-next 6/6] net: mvpp2: Consider NVMEM cells as possible
 MAC address source

Hi Miquel,


czw., 17 lis 2022 o 22:56 Miquel Raynal <miquel.raynal@...tlin.com> napisał(a):
>
> The ONIE standard describes the organization of tlv (type-length-value)
> arrays commonly stored within NVMEM devices on common networking
> hardware.
>
> Several drivers already make use of NVMEM cells for purposes like
> retrieving a default MAC address provided by the manufacturer.
>
> What made ONIE tables unusable so far was the fact that the information
> where "dynamically" located within the table depending on the
> manufacturer wishes, while Linux NVMEM support only allowed statically
> defined NVMEM cells. Fortunately, this limitation was eventually tackled
> with the introduction of discoverable cells through the use of NVMEM
> layouts, making it possible to extract and consistently use the content
> of tables like ONIE's tlv arrays.
>
> Parsing this table at runtime in order to get various information is now
> possible. So, because many Marvell networking switches already follow
> this standard, let's consider using NVMEM cells as a new valid source of
> information when looking for a base MAC address, which is one of the
> primary uses of these new fields. Indeed, manufacturers following the
> ONIE standard are encouraged to provide a default MAC address there, so
> let's eventually use it if no other MAC address has been found using the
> existing methods.
>
> Link: https://opencomputeproject.github.io/onie/design-spec/hw_requirements.html

Thanks for the patch. Did you manage to test in on a real HW? I am curious about

> Signed-off-by: Miquel Raynal <miquel.raynal@...tlin.com>
> ---
>  drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c | 6 ++++++
>  1 file changed, 6 insertions(+)
>
> diff --git a/drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c b/drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c
> index eb0fb8128096..7c8c323f4411 100644
> --- a/drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c
> +++ b/drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c
> @@ -6104,6 +6104,12 @@ static void mvpp2_port_copy_mac_addr(struct net_device *dev, struct mvpp2 *priv,
>                 }
>         }
>
> +       if (!of_get_mac_address(to_of_node(fwnode), hw_mac_addr)) {

Unfortunately, nvmem cells seem to be not supported with ACPI yet, so
we cannot extend fwnode_get_mac_address - I think it should be,
however, an end solution.

As of now, I'd prefer to use of_get_mac_addr_nvmem directly, to avoid
parsing the DT again (after fwnode_get_mac_address) and relying
implicitly on falling back to nvmem stuff (currently, without any
comment it is not obvious).

Best regards,
Marcin

> +               *mac_from = "nvmem cell";
> +               eth_hw_addr_set(dev, hw_mac_addr);
> +               return;
> +       }
> +
>         *mac_from = "random";
>         eth_hw_addr_random(dev);
>  }
> --
> 2.34.1
>