linux-kernel - Re: [PATCH 2/2] net: phy: Add driver for Motorcomm yt8821 2.5G ethernet phy

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Message-ID: <c44be0f3-7850-4038-bffb-942a85e3c7d0@motor-comm.com>
Date: Sun, 11 Aug 2024 06:58:54 -0700
From: "Frank.Sae" <Frank.Sae@...or-comm.com>
To: "Russell King (Oracle)" <linux@...linux.org.uk>
Cc: andrew@...n.ch, hkallweit1@...il.com, davem@...emloft.net,
 edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com, robh@...nel.org,
 krzk+dt@...nel.org, conor+dt@...nel.org, netdev@...r.kernel.org,
 devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
 yuanlai.cui@...or-comm.com, hua.sun@...or-comm.com,
 xiaoyong.li@...or-comm.com, suting.hu@...or-comm.com, jie.han@...or-comm.com
Subject: Re: [PATCH 2/2] net: phy: Add driver for Motorcomm yt8821 2.5G
 ethernet phy


On 7/29/24 04:41, Russell King (Oracle) wrote:
> On Sat, Jul 27, 2024 at 02:20:31AM -0700, Frank.Sae wrote:
>> +/**
>> + * yt8821_config_init() - phy initializatioin
>> + * @phydev: a pointer to a &struct phy_device
>> + *
>> + * returns 0 or negative errno code
>> + */
>> +static int yt8821_config_init(struct phy_device *phydev)
>> +{
>> +	struct yt8821_priv *priv = phydev->priv;
>> +	int ret, val;
>> +
>> +	phydev->irq = PHY_POLL;
>> +
>> +	val = ytphy_read_ext_with_lock(phydev, YT8521_CHIP_CONFIG_REG);
>> +	if (priv->chip_mode == YT8821_CHIP_MODE_AUTO_BX2500_SGMII) {
>> +		ret = ytphy_modify_ext_with_lock(phydev,
>> +						 YT8521_CHIP_CONFIG_REG,
>> +						 YT8521_CCR_MODE_SEL_MASK,
>> +						 FIELD_PREP(YT8521_CCR_MODE_SEL_MASK, 0));
>> +		if (ret < 0)
>> +			return ret;
>> +
>> +		__assign_bit(PHY_INTERFACE_MODE_2500BASEX,
>> +			     phydev->possible_interfaces,
>> +			     true);
>> +		__assign_bit(PHY_INTERFACE_MODE_SGMII,
>> +			     phydev->possible_interfaces,
>> +			     true);
> Before each and every call to .config_init, phydev->possible_interfaces
> will be cleared. So, please use __set_bit() here.
>
>> +static int yt8821_read_status(struct phy_device *phydev)
>> +{
>> +	struct yt8821_priv *priv = phydev->priv;
>> +	int old_page;
>> +	int ret = 0;
>> +	int link;
>> +	int val;
>> +
>> +	if (phydev->autoneg == AUTONEG_ENABLE) {
>> +		int lpadv = phy_read_mmd(phydev,
>> +					 MDIO_MMD_AN, MDIO_AN_10GBT_STAT);
>> +
>> +		if (lpadv < 0)
>> +			return lpadv;
>> +
>> +		mii_10gbt_stat_mod_linkmode_lpa_t(phydev->lp_advertising,
>> +						  lpadv);
>> +	}
>> +
>> +	ret = ytphy_write_ext_with_lock(phydev,
>> +					YT8521_REG_SPACE_SELECT_REG,
>> +					YT8521_RSSR_UTP_SPACE);
>> +	if (ret < 0)
>> +		return ret;
>> +
>> +	ret = genphy_read_status(phydev);
>> +	if (ret < 0)
>> +		return ret;
>> +
>> +	old_page = phy_select_page(phydev, YT8521_RSSR_UTP_SPACE);
>> +	if (old_page < 0)
>> +		goto err_restore_page;
>> +
>> +	val = __phy_read(phydev, YTPHY_SPECIFIC_STATUS_REG);
>> +	if (val < 0) {
>> +		ret = val;
>> +		goto err_restore_page;
>> +	}
>> +
>> +	link = val & YTPHY_SSR_LINK;
> What link status is this reporting? For interface switching to work,
> phydev->link must _only_ indicate whether the _media_ side interface
> is up or down. It must _not_ include the status of the MAC facing
> interface from the PHY.
>
> Why? The interface configuration of the MAC is only performed when
> the _media_ link comes up, denoted by phydev->link becoming true.
> If the MAC interface configuration mismatches the PHY interface
> configuration, then the MAC facing interface of the PHY will
> remain down, and if phydev->link is forced to false, then the link
> will never come up.
>
> So, I hope that this isn't testing the MAC facing interface status
> of the PHY!
>
MAC facing interface will be switched according to phy interface. when phy
media side state is link down, the mac facing interface will not be
configured, this refers to Marvell10g.c(mv3310_update_interface) and
Realtek.c(rtl822xb_update_interface).