linux-kernel - Re: [PATCH 1/3] net: phy: MII-Lite PHY interface mode

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Message-ID: <aF1E2G69T4IlkCl9@shell.armlinux.org.uk>
Date: Thu, 26 Jun 2025 14:02:16 +0100
From: "Russell King (Oracle)" <linux@...linux.org.uk>
To: Kamil Horák - 2N <kamilh@...s.com>
Cc: florian.fainelli@...adcom.com, bcm-kernel-feedback-list@...adcom.com,
	andrew@...n.ch, hkallweit1@...il.com, davem@...emloft.net,
	edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com,
	krzk+dt@...nel.org, conor+dt@...nel.org, netdev@...r.kernel.org,
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
	f.fainelli@...il.com, robh@...nel.org, andrew+netdev@...n.ch
Subject: Re: [PATCH 1/3] net: phy: MII-Lite PHY interface mode

On Thu, Jun 26, 2025 at 01:56:17PM +0200, Kamil Horák - 2N wrote:
> diff --git a/drivers/net/phy/broadcom.c b/drivers/net/phy/broadcom.c
> index 9b1de54fd483..7d3b85a07b8c 100644
> --- a/drivers/net/phy/broadcom.c
> +++ b/drivers/net/phy/broadcom.c
> @@ -423,6 +423,13 @@ static int bcm54811_config_init(struct phy_device *phydev)
>  	/* With BCM54811, BroadR-Reach implies no autoneg */
>  	if (priv->brr_mode)
>  		phydev->autoneg = 0;

Blank line here to aid readability please.

> +	/* Enable MII Lite (No TXER, RXER, CRS, COL) if configured */
> +	err = bcm_phy_modify_exp(phydev, BCM_EXP_SYNC_ETHERNET,
> +				 BCM_EXP_SYNC_ETHERNET_MII_LITE,
> +				 phydev->interface == PHY_INTERFACE_MODE_MIILITE ?
> +				 BCM_EXP_SYNC_ETHERNET_MII_LITE : 0);

In cases like this, where the ternary op leads to less readable code,
it's better to do:

	if (phydev->interface == PHY_INTERFACE_MODE_MIILITE)
		exp_sync_ethernet = BCM_EXP_SYNC_ETHERNET_MII_LITE;
	else
		exp_sync_ethernet = 0;

	err = bcm_phy_modify_exp(phydev, BCM_EXP_SYNC_ETHERNET,
				 BCM_EXP_SYNC_ETHERNET_MII_LITE,
				 exp_sync_ethernet);

> +	if (err < 0)
> +		return err;
>  
>  	return bcm5481x_set_brrmode(phydev, priv->brr_mode);
>  }

I'd include this with the above change:

> diff --git a/include/linux/brcmphy.h b/include/linux/brcmphy.h
> index 028b3e00378e..15c35655f482 100644
> --- a/include/linux/brcmphy.h
> +++ b/include/linux/brcmphy.h
> @@ -182,6 +182,12 @@
>  #define BCM_LED_MULTICOLOR_ACT		0x9
>  #define BCM_LED_MULTICOLOR_PROGRAM	0xa
>  
> +/*
> + * Broadcom Synchronous Ethernet Controls (expansion register 0x0E)
> + */
> +#define BCM_EXP_SYNC_ETHERNET		(MII_BCM54XX_EXP_SEL_ER + 0x0E)
> +#define BCM_EXP_SYNC_ETHERNET_MII_LITE	BIT(11)
> +
>  /*
>   * BCM5482: Shadow registers
>   * Shadow values go into bits [14:10] of register 0x1c to select a shadow

... and send the changes below as a separate patch as these changes
below are modifying generic code.

> diff --git a/drivers/net/phy/phy-core.c b/drivers/net/phy/phy-core.c
> index e177037f9110..b2df06343b7e 100644
> --- a/drivers/net/phy/phy-core.c
> +++ b/drivers/net/phy/phy-core.c
> @@ -115,6 +115,7 @@ int phy_interface_num_ports(phy_interface_t interface)
>  		return 0;
>  	case PHY_INTERFACE_MODE_INTERNAL:
>  	case PHY_INTERFACE_MODE_MII:
> +	case PHY_INTERFACE_MODE_MIILITE:
>  	case PHY_INTERFACE_MODE_GMII:
>  	case PHY_INTERFACE_MODE_TBI:
>  	case PHY_INTERFACE_MODE_REVMII:
> diff --git a/drivers/net/phy/phy_caps.c b/drivers/net/phy/phy_caps.c
> index 38417e288611..b4a4dea3e756 100644
> --- a/drivers/net/phy/phy_caps.c
> +++ b/drivers/net/phy/phy_caps.c
> @@ -316,6 +316,10 @@ unsigned long phy_caps_from_interface(phy_interface_t interface)
>  		link_caps |= BIT(LINK_CAPA_100HD) | BIT(LINK_CAPA_100FD);
>  		break;
>  
> +	case PHY_INTERFACE_MODE_MIILITE:
> +		link_caps |= BIT(LINK_CAPA_10FD) | BIT(LINK_CAPA_100FD);
> +		break;
> +
>  	case PHY_INTERFACE_MODE_TBI:
>  	case PHY_INTERFACE_MODE_MOCA:
>  	case PHY_INTERFACE_MODE_RTBI:
> diff --git a/drivers/net/phy/phylink.c b/drivers/net/phy/phylink.c
> index 0faa3d97e06b..766cad40f1b8 100644
> --- a/drivers/net/phy/phylink.c
> +++ b/drivers/net/phy/phylink.c
> @@ -234,6 +234,7 @@ static int phylink_interface_max_speed(phy_interface_t interface)
>  	case PHY_INTERFACE_MODE_SMII:
>  	case PHY_INTERFACE_MODE_REVMII:
>  	case PHY_INTERFACE_MODE_MII:
> +	case PHY_INTERFACE_MODE_MIILITE:
>  		return SPEED_100;
>  
>  	case PHY_INTERFACE_MODE_TBI:
> diff --git a/include/linux/phy.h b/include/linux/phy.h
> index e194dad1623d..6aad4b741c01 100644
> --- a/include/linux/phy.h
> +++ b/include/linux/phy.h
> @@ -103,6 +103,7 @@ extern const int phy_basic_ports_array[3];
>   * @PHY_INTERFACE_MODE_QUSGMII: Quad Universal SGMII
>   * @PHY_INTERFACE_MODE_1000BASEKX: 1000Base-KX - with Clause 73 AN
>   * @PHY_INTERFACE_MODE_10G_QXGMII: 10G-QXGMII - 4 ports over 10G USXGMII
> + * @PHY_INTERFACE_MODE_MIILITE: MII-Lite - MII without RXER TXER CRS COL
>   * @PHY_INTERFACE_MODE_MAX: Book keeping
>   *
>   * Describes the interface between the MAC and PHY.
> @@ -144,6 +145,7 @@ typedef enum {
>  	PHY_INTERFACE_MODE_QUSGMII,
>  	PHY_INTERFACE_MODE_1000BASEKX,
>  	PHY_INTERFACE_MODE_10G_QXGMII,
> +	PHY_INTERFACE_MODE_MIILITE,
>  	PHY_INTERFACE_MODE_MAX,
>  } phy_interface_t;
>  
> @@ -260,6 +262,8 @@ static inline const char *phy_modes(phy_interface_t interface)
>  		return "qusgmii";
>  	case PHY_INTERFACE_MODE_10G_QXGMII:
>  		return "10g-qxgmii";
> +	case PHY_INTERFACE_MODE_MIILITE:
> +		return "mii-lite";
>  	default:
>  		return "unknown";
>  	}

Otherwise, I think this is fine.

Please remember netdev's rules, which can be found in the tl;dr on:
https://www.kernel.org/doc/html/v6.1/process/maintainer-netdev.html

(There's probably an updated version, but I can never remember the URL.)

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
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