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

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Message-ID: <850e769c-ea03-4777-b91b-c7a8b0ad6455@iscas.ac.cn>
Date: Sun, 14 Sep 2025 11:54:38 +0800
From: Vivian Wang <wangruikang@...as.ac.cn>
To: Andrew Lunn <andrew@...n.ch>
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

On 9/13/25 05:10, Andrew Lunn wrote:
>> +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?

This should be fine, since most of the registers only have lower 16
bits, and the upper 16 bits ignores writes and read as zeros. But I'll
change it to a FIELD_GET for v12 just so there's no question on whether
this is safe.

Thanks,
Vivian "dramforever" Wang

> 	Andrew