linux-kernel - Re: [PATCH 3/3] net: phy: mediatek: add support for built-in 2.5G ethernet PHY on MT7988

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Date: Wed, 8 May 2024 10:56:25 +0000
From: SkyLake Huang (黃啟澤)
	<SkyLake.Huang@...iatek.com>
To: "linux@...linux.org.uk" <linux@...linux.org.uk>
CC: "andrew@...n.ch" <andrew@...n.ch>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>, "linux-mediatek@...ts.infradead.org"
	<linux-mediatek@...ts.infradead.org>, "linux-arm-kernel@...ts.infradead.org"
	<linux-arm-kernel@...ts.infradead.org>, "kuba@...nel.org" <kuba@...nel.org>,
	"pabeni@...hat.com" <pabeni@...hat.com>, "edumazet@...gle.com"
	<edumazet@...gle.com>, "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"dqfext@...il.com" <dqfext@...il.com>,
	Steven Liu (劉人豪) <steven.liu@...iatek.com>,
	"matthias.bgg@...il.com" <matthias.bgg@...il.com>, "davem@...emloft.net"
	<davem@...emloft.net>, "hkallweit1@...il.com" <hkallweit1@...il.com>,
	"daniel@...rotopia.org" <daniel@...rotopia.org>,
	"angelogioacchino.delregno@...labora.com"
	<angelogioacchino.delregno@...labora.com>
Subject: Re: [PATCH 3/3] net: phy: mediatek: add support for built-in 2.5G
 ethernet PHY on MT7988

On Thu, 2024-04-25 at 10:01 +0100, Russell King (Oracle) wrote:
>  	 
> External email : Please do not click links or open attachments until
> you have verified the sender or the content.
>  On Thu, Apr 25, 2024 at 10:33:25AM +0800, Sky Huang wrote:
> > +static int mt7988_2p5ge_phy_config_init(struct phy_device *phydev)
> > +{
> > +int ret, i;
> > +const struct firmware *fw;
> > +struct device *dev = &phydev->mdio.dev;
> > +struct device_node *np;
> > +void __iomem *pmb_addr;
> > +void __iomem *md32_en_cfg_base;
> > +struct mtk_i2p5ge_phy_priv *priv = phydev->priv;
> > +u16 reg;
> > +struct pinctrl *pinctrl;
> > +
> > +if (!priv->fw_loaded) {
> > +np = of_find_compatible_node(NULL, NULL, "mediatek,2p5gphy-fw");
> > +if (!np)
> > +return -ENOENT;
> > +pmb_addr = of_iomap(np, 0);
> > +if (!pmb_addr)
> > +return -ENOMEM;
> > +md32_en_cfg_base = of_iomap(np, 1);
> > +if (!md32_en_cfg_base)
> > +return -ENOMEM;
> 
> Wouldn't it be better to do this in the probe function rather than
> here?
> 
Agree. I'll move this to probe function in v2.

> > +
> > +ret = request_firmware(&fw, MT7988_2P5GE_PMB, dev);
> > +if (ret) {
> > +dev_err(dev, "failed to load firmware: %s, ret: %d\n",
> > +MT7988_2P5GE_PMB, ret);
> > +return ret;
> > +}
> 
> This will block for userspace while holding phydev->lock and the
> RTNL.
> That blocks much of the networking APIs, which is not a good idea. If
> you have a number of these PHYs, then the RTNL will serialise the
> loading of firmware.
> 
I'm not sure I really get this. MT7988's internal 2.5Gphy is built
inside SoC. We won't have a number of these PHYs.

> > +
> > +reg = readw(md32_en_cfg_base);
> > +if (reg & MD32_EN) {
> > +phy_set_bits(phydev, 0, BIT(15));
> 
> This is probably the BMCR, so if it is, please use the established
> definitions.
> 
> > +usleep_range(10000, 11000);
> > +}
> > +phy_set_bits(phydev, 0, BIT(11));
> 
> This also looks like it's probably the BMCR.
> 
> > +
> > +/* Write magic number to safely stall MCU */
> > +phy_write_mmd(phydev, MDIO_MMD_VEND1, 0x800e, 0x1100);
> > +phy_write_mmd(phydev, MDIO_MMD_VEND1, 0x800f, 0x00df);
> > +
> > +for (i = 0; i < fw->size - 1; i += 4)
> > +writel(*((uint32_t *)(fw->data + i)), pmb_addr + i);
> > +release_firmware(fw);
> > +
> > +writew(reg & ~MD32_EN, md32_en_cfg_base);
> > +writew(reg | MD32_EN, md32_en_cfg_base);
> > +phy_set_bits(phydev, 0, BIT(15));
> 
> And also probably the BMCR.
> 
Thanks. I'll change these to corresponding BMCR definitions in v2.

> -- 
> RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
> FTTP is here! 80Mbps down 10Mbps up. Decent connectivity at last!