netdev - [PATCH 5/5] net: mvpp2: Consider NVMEM cells as possible MAC address source

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Message-Id: <20221028092337.822840-6-miquel.raynal@bootlin.com>
Date:   Fri, 28 Oct 2022 11:23:37 +0200
From:   Miquel Raynal <miquel.raynal@...tlin.com>
To:     Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
        <linux-kernel@...r.kernel.org>, Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        devicetree@...r.kernel.org
Cc:     Marcin Wojtas <mw@...ihalf.com>,
        Russell King <linux@...linux.org.uk>,
        Maxime Chevallier <maxime.chevallier@...tlin.com>,
        "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,
        Robert Marko <robert.marko@...tura.hr>,
        Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
        Michael Walle <michael@...le.cc>,
        Miquel Raynal <miquel.raynal@...tlin.com>
Subject: [PATCH 5/5] net: mvpp2: Consider NVMEM cells as possible MAC address source

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
Signed-off-by: Miquel Raynal <miquel.raynal@...tlin.com>
---

Hello, I suppose my change is safe but I don't want to break existing
setups so a review on this would be welcome!

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