netdev - Re: [PATCH net v3 1/2] net: phy: micrel: lan8842 errata

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Message-ID: <20251031075411.kcxdfonu42wj5rjh@DEN-DL-M31836.microchip.com>
Date: Fri, 31 Oct 2025 08:54:11 +0100
From: Horatiu Vultur <horatiu.vultur@...rochip.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>,
	<netdev@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH net v3 1/2] net: phy: micrel: lan8842 errata

The 10/30/2025 10:33, Russell King (Oracle) wrote:

Hi Russell,

> 
> On Thu, Oct 30, 2025 at 08:49:40AM +0100, Horatiu Vultur wrote:
> > +static int lan8842_erratas(struct phy_device *phydev)
> > +{
> > +     int ret;
> > +
> > +     /* Magjack center tapped ports */
> > +     ret = lanphy_write_page_reg(phydev, LAN8814_PAGE_POWER_REGS,
> > +                                 LAN8814_POWER_MGMT_MODE_3_ANEG_MDI,
> > +                                 LAN8814_POWER_MGMT_VAL1);
> > +     if (ret < 0)
> > +             return ret;
> > +
> > +     ret = lanphy_write_page_reg(phydev, LAN8814_PAGE_POWER_REGS,
> > +                                 LAN8814_POWER_MGMT_MODE_4_ANEG_MDIX,
> > +                                 LAN8814_POWER_MGMT_VAL1);
> > +     if (ret < 0)
> > +             return ret;
> > +
> > +     ret = lanphy_write_page_reg(phydev, LAN8814_PAGE_POWER_REGS,
> > +                                 LAN8814_POWER_MGMT_MODE_5_10BT_MDI,
> > +                                 LAN8814_POWER_MGMT_VAL1);
> > +     if (ret < 0)
> > +             return ret;
> > +
> > +     ret = lanphy_write_page_reg(phydev, LAN8814_PAGE_POWER_REGS,
> > +                                 LAN8814_POWER_MGMT_MODE_6_10BT_MDIX,
> > +                                 LAN8814_POWER_MGMT_VAL1);
> > +     if (ret < 0)
> > +             return ret;
> > +
> > +     ret = lanphy_write_page_reg(phydev, LAN8814_PAGE_POWER_REGS,
> > +                                 LAN8814_POWER_MGMT_MODE_7_100BT_TRAIN,
> > +                                 LAN8814_POWER_MGMT_VAL2);
> > +     if (ret < 0)
> > +             return ret;
> > +
> > +     ret = lanphy_write_page_reg(phydev, LAN8814_PAGE_POWER_REGS,
> > +                                 LAN8814_POWER_MGMT_MODE_8_100BT_MDI,
> > +                                 LAN8814_POWER_MGMT_VAL3);
> > +     if (ret < 0)
> > +             return ret;
> > +
> > +     ret = lanphy_write_page_reg(phydev, LAN8814_PAGE_POWER_REGS,
> > +                                 LAN8814_POWER_MGMT_MODE_9_100BT_EEE_MDI_TX,
> > +                                 LAN8814_POWER_MGMT_VAL3);
> > +     if (ret < 0)
> > +             return ret;
> > +
> > +     ret = lanphy_write_page_reg(phydev, LAN8814_PAGE_POWER_REGS,
> > +                                 LAN8814_POWER_MGMT_MODE_10_100BT_EEE_MDI_RX,
> > +                                 LAN8814_POWER_MGMT_VAL4);
> > +     if (ret < 0)
> > +             return ret;
> > +
> > +     ret = lanphy_write_page_reg(phydev, LAN8814_PAGE_POWER_REGS,
> > +                                 LAN8814_POWER_MGMT_MODE_11_100BT_MDIX,
> > +                                 LAN8814_POWER_MGMT_VAL5);
> > +     if (ret < 0)
> > +             return ret;
> > +
> > +     ret = lanphy_write_page_reg(phydev, LAN8814_PAGE_POWER_REGS,
> > +                                 LAN8814_POWER_MGMT_MODE_12_100BT_EEE_MDIX_TX,
> > +                                 LAN8814_POWER_MGMT_VAL5);
> > +     if (ret < 0)
> > +             return ret;
> > +
> > +     ret = lanphy_write_page_reg(phydev, LAN8814_PAGE_POWER_REGS,
> > +                                 LAN8814_POWER_MGMT_MODE_13_100BT_EEE_MDIX_RX,
> > +                                 LAN8814_POWER_MGMT_VAL4);
> > +     if (ret < 0)
> > +             return ret;
> > +
> > +     return lanphy_write_page_reg(phydev, LAN8814_PAGE_POWER_REGS,
> > +                                  LAN8814_POWER_MGMT_MODE_14_100BTX_EEE_TX_RX,
> > +                                  LAN8814_POWER_MGMT_VAL4);
> 
> This is a lot of repetition.
> 
> Is it worth storing the errata register information in a struct, and
> then using a loop to write these registers. Something like:
> 
> struct lanphy_reg_data {
>         int page;
>         u16 addr;
>         u16 val;
> ;
> 
> static const struct lanphy_reg_data short_centre_tap_errata[] = {
>         ...
> };
> 
> static int lanphy_write_reg_data(struct phy_device *phydev,
>                                  const struct lanphy_reg_data *data,
>                                  size_t num)
> {
>         int ret = 0;
> 
>         while (num--) {
>                 ret = lanphy_write_page_reg(phydev, data->page, data->addr,
>                                             data->val);
>                 if (ret)
>                         break;
>         }
> 
>         return 0;
> }
> 
> static int lan8842_erratas(struct phy_device *phydev)
> {
>         int ret;
> 
>         ret = lanphy_write_reg_data(phydev, short_centre_tap_errata,
>                                     ARRAY_SIZE(short_centre_tap_errata));
>         if (ret)
>                 return ret;
> 
>         return lanphy_write_reg_data(phydev, blah_errata,
>                                      ARRAY_SIZE(blah_errata));
> }
> 
> ?

That is a really good suggestion. I will do that in the next version.

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

-- 
/Horatiu