linux-kernel - Re: [PATCH net-next v11 2/5] net: spacemit: Add K1 Ethernet MAC

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Message-ID: <1f2887e4-2644-48a4-8171-98bd310d190f@lunn.ch>
Date: Fri, 12 Sep 2025 23:10:51 +0200
From: Andrew Lunn <andrew@...n.ch>
To: Vivian Wang <wangruikang@...as.ac.cn>
Cc: Andrew Lunn <andrew+netdev@...n.ch>, Jakub Kicinski <kuba@...nel.org>,
	Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>, Yixun Lan <dlan@...too.org>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>, Paolo Abeni <pabeni@...hat.com>,
	Philipp Zabel <p.zabel@...gutronix.de>,
	Paul Walmsley <paul.walmsley@...ive.com>,
	Palmer Dabbelt <palmer@...belt.com>,
	Albert Ou <aou@...s.berkeley.edu>, Alexandre Ghiti <alex@...ti.fr>,
	Vivian Wang <uwu@...m.page>,
	Vadim Fedorenko <vadim.fedorenko@...ux.dev>,
	Junhui Liu <junhui.liu@...moral.tech>,
	Simon Horman <horms@...nel.org>,
	Maxime Chevallier <maxime.chevallier@...tlin.com>,
	netdev@...r.kernel.org, devicetree@...r.kernel.org,
	linux-riscv@...ts.infradead.org, spacemit@...ts.linux.dev,
	linux-kernel@...r.kernel.org,
	Troy Mitchell <troy.mitchell@...ux.spacemit.com>
Subject: Re: [PATCH net-next v11 2/5] net: spacemit: Add K1 Ethernet MAC

> +static u32 emac_rd(struct emac_priv *priv, u32 reg)
> +{
> +	return readl(priv->iobase + reg);
> +}

> +static int emac_mii_read(struct mii_bus *bus, int phy_addr, int regnum)
> +{
> +	struct emac_priv *priv = bus->priv;
> +	u32 cmd = 0, val;
> +	int ret;
> +
> +	cmd |= FIELD_PREP(MREGBIT_PHY_ADDRESS, phy_addr);
> +	cmd |= FIELD_PREP(MREGBIT_REGISTER_ADDRESS, regnum);
> +	cmd |= MREGBIT_START_MDIO_TRANS | MREGBIT_MDIO_READ_WRITE;
> +
> +	emac_wr(priv, MAC_MDIO_DATA, 0x0);
> +	emac_wr(priv, MAC_MDIO_CONTROL, cmd);
> +
> +	ret = readl_poll_timeout(priv->iobase + MAC_MDIO_CONTROL, val,
> +				 !(val & MREGBIT_START_MDIO_TRANS), 100, 10000);
> +
> +	if (ret)
> +		return ret;
> +
> +	val = emac_rd(priv, MAC_MDIO_DATA);
> +	return val;

emac_rd() returns a u32. Is it guaranteed by the hardware that the
upper word is 0? Maybe this needs to be masked?

	Andrew