netdev - Re: [PATCH net-next v2 5/5] net: phy: add driver for built-in 2.5G ethernet PHY on MT7988

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Message-ID: <cc0f67de-171e-45e1-90d9-b6b40ec71827@lunn.ch>
Date: Sat, 18 May 2024 03:29:34 +0200
From: Andrew Lunn <andrew@...n.ch>
To: Sky Huang <SkyLake.Huang@...iatek.com>
Cc: Heiner Kallweit <hkallweit1@...il.com>,
	Russell King <linux@...linux.org.uk>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Daniel Golle <daniel@...rotopia.org>,
	Qingfang Deng <dqfext@...il.com>,
	Matthias Brugger <matthias.bgg@...il.com>,
	AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>,
	linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	linux-mediatek@...ts.infradead.org,
	Steven Liu <Steven.Liu@...iatek.com>
Subject: Re: [PATCH net-next v2 5/5] net: phy: add driver for built-in 2.5G
 ethernet PHY on MT7988

> +static int mt798x_2p5ge_phy_config_init(struct phy_device *phydev)
> +{
> +	struct mtk_i2p5ge_phy_priv *priv = phydev->priv;
> +	struct device *dev = &phydev->mdio.dev;
> +	const struct firmware *fw;
> +	struct pinctrl *pinctrl;
> +	int ret, i;
> +	u16 reg;
> +
> +	if (!priv->fw_loaded) {
> +		if (!priv->md32_en_cfg_base || !priv->pmb_addr) {
> +			dev_err(dev, "MD32_EN_CFG base & PMB addresses aren't valid\n");
> +			return -EINVAL;
> +		}
> +
> +		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;
> +		}
> +
> +		reg = readw(priv->md32_en_cfg_base);
> +		if (reg & MD32_EN) {
> +			phy_set_bits(phydev, MII_BMCR, BMCR_RESET);
> +			usleep_range(10000, 11000);
> +		}
> +		phy_set_bits(phydev, MII_BMCR, BMCR_PDOWN);
> +
> +		/* 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)), priv->pmb_addr + i);

You should not trust the firmware. At least do a range check. How big
is the SRAM the firmware is being written into? If you are given a
firmware which is 1MB in size, what will happen?

> +		release_firmware(fw);
> +
> +		writew(reg & ~MD32_EN, priv->md32_en_cfg_base);
> +		writew(reg | MD32_EN, priv->md32_en_cfg_base);
> +		phy_set_bits(phydev, MII_BMCR, BMCR_RESET);
> +		/* We need a delay here to stabilize initialization of MCU */
> +		usleep_range(7000, 8000);
> +		dev_info(dev, "Firmware loading/trigger ok.\n");

Is there a version available anywhere for the firmware?

> +static int mt798x_2p5ge_phy_get_features(struct phy_device *phydev)
> +{
> +	int ret;
> +
> +	ret = genphy_c45_pma_read_abilities(phydev);
> +	if (ret)
> +		return ret;
> +
> +	/* We don't support HDX at MAC layer on mt7988.

That is a MAC limitation, so it should be the MAC which disables this,
not the Phy.

> +	/* FIXME: AN device (MDIO_DEVS_AN)is indeed in this package. However, MDIO_DEVS_AN seems
> +	 * that it won't be set as we detect phydev->c45_ids.mmds_present. So Autoneg_BIT won't be
> +	 * set in genphy_c45_pma_read_abilities(), either. Workaround here temporarily.
> +	 */
> +	linkmode_set_bit(ETHTOOL_LINK_MODE_Autoneg_BIT, phydev->supported);
> +
> +	return 0;
> +}
> +
> +static int mt798x_2p5ge_phy_read_status(struct phy_device *phydev)
> +{
> +	u16 bmsr;
> +	int ret;
> +
> +	/* Use this instead of genphy_c45_read_link() because MDIO_DEVS_AN bit isn't set in
> +	 * phydev->c45_ids.mmds_present.

You have this twice now. Is the hardware broken? If so, maybe change
phydev->c45_ids.mmds_present in the probe function to set the bit?

> +	 */
> +	ret = genphy_update_link(phydev);
> +	if (ret)
> +		return ret;
> +
> +	phydev->speed = SPEED_UNKNOWN;
> +	phydev->duplex = DUPLEX_UNKNOWN;
> +	phydev->pause = 0;
> +	phydev->asym_pause = 0;
> +
> +	/* We'll read link speed through vendor specific registers down below. So remove
> +	 * phy_resolve_aneg_linkmode (AN on) & genphy_c45_read_pma (AN off).
> +	 */
> +	if (phydev->autoneg == AUTONEG_ENABLE && phydev->autoneg_complete) {
> +		ret = genphy_c45_read_lpa(phydev);
> +		if (ret < 0)
> +			return ret;
> +
> +		/* Clause 45 doesn't define 1000BaseT support. Read the link partner's 1G
> +		 * advertisement via Clause 22
> +		 */
> +		ret = phy_read(phydev, MII_STAT1000);
> +		if (ret < 0)
> +			return ret;
> +		mii_stat1000_mod_linkmode_lpa_t(phydev->lp_advertising, ret);
> +	} else if (phydev->autoneg == AUTONEG_DISABLE) {
> +		/* Mask link partner's all advertising capabilities when AN is off. In fact,
> +		 * if we disable antuneg, we can't link up correctly:
> +		 *   2.5G/1G: Need AN to exchange master/slave information.
> +		 *   100M: Without AN, link starts at half duplex, which this phy doesn't support.
> +		 *   10M: Deprecated in this ethernet phy.
> +		 */

So it sounds like phydev->autoneg == AUTONEG_DISABLE is broken with
this hardware. So just don't allow it, return -EOPNOTSUPP in config_aneg()

     Andrew