Re: [PATCH net-next v4 4/4] net: phy: micrel: Add support for lan8842

The 08/14/2025 10:20, Russell King (Oracle) wrote:

Hi Russell,

On Thu, Aug 14, 2025 at 10:26:24AM +0200, Horatiu Vultur wrote:

quoted

+static int lan8842_config_init(struct phy_device *phydev)
+{
+     int ret;
+
+     /* Reset the PHY */
+     ret = lanphy_modify_page_reg(phydev, LAN8814_PAGE_COMMON_REGS,
+                                  LAN8814_QSGMII_SOFT_RESET,
+                                  LAN8814_QSGMII_SOFT_RESET_BIT,
+                                  LAN8814_QSGMII_SOFT_RESET_BIT);
+     if (ret < 0)
+             return ret;
+
+     /* Disable ANEG with QSGMII PCS Host side
+      * It has the same address as lan8814
+      */
+     ret = lanphy_modify_page_reg(phydev, LAN8814_PAGE_PORT_REGS,
+                                  LAN8814_QSGMII_PCS1G_ANEG_CONFIG,
+                                  LAN8814_QSGMII_PCS1G_ANEG_CONFIG_ANEG_ENA,
+                                  0);
+     if (ret < 0)
+             return ret;

Could you explain exactly what effect this has please?

The effect of this and the next write is to disable the auto-negotiation
between the PHY and the MAC.

quoted

+
+     /* Disable also the SGMII_AUTO_ANEG_ENA, this will determine what is the
+      * PHY autoneg with the other end and then will update the host side
+      */
+     ret = lanphy_write_page_reg(phydev, LAN8814_PAGE_COMMON_REGS,
+                                 LAN8842_SGMII_AUTO_ANEG_ENA, 0);
+     if (ret < 0)
+             return ret;

Also please explain this a bit more.

This write disables the PHY to update the host side advertise abilities
with what it autonegotiate on the link side. I will need to double check
but I think this is not needed if the autonegotiation on the host side
is already disabled.

If this changes whether host-side "negotiation" is used, then please
consider implementing the two phy driver inbnad operations as well.

Yes, I will implement the functions: config_inband and inband_caps.

quoted

+static u64 lan8842_get_stat(struct phy_device *phydev, int count, int *regs)
+{
+     int val;

i> +    u64 ret = 0;

Please remember... reverse Christmas tree for variable declarations.

Argh.. goot catch!

Thanks.

--
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-- 
/Horatiu