Microchip lan7431 is frequently connected to a phy. However, it
can also be directly connected to a MII remote peer without
any phy in between. For supporting such a phyless hardware setup
in Linux we added the capability to the driver to understand
the fixed-link and the phy-connection-type entries in the device
tree.

If a fixed-link node is configured in the device tree the lan7431
device will deactivate auto negotiation and uses the speed and
duplex settings configured in the fixed-link node.

Also the phy-connection-type can be configured in the device tree
and in case of a fixed-link connection the RGMII mode can be
configured, all other modes fall back to the default: GMII.

Example:

 &pcie {
        status = "okay";

        host@0 {
                reg = <0 0 0 0 0>;

                #address-cells = <3>;
                #size-cells = <2>;

                ethernet@0 {
                        compatible = "weyland-yutani,noscom1", 
"microchip,lan743x";
                        status = "okay";
                        reg = <0 0 0 0 0>;
                        phy-connection-type = "rgmii";

                        fixed-link {
                                speed = <100>;
                                full-duplex;
                        };
                };
        };
};

Signed-off-by: Roelof Berg <rb...@berg-solutions.de>
---
 drivers/net/ethernet/microchip/lan743x_main.c | 93 +++++++++++++++++--
 drivers/net/ethernet/microchip/lan743x_main.h |  4 +
 2 files changed, 89 insertions(+), 8 deletions(-)

diff --git a/drivers/net/ethernet/microchip/lan743x_main.c 
b/drivers/net/ethernet/microchip/lan743x_main.c
index a43140f7b5eb..278765dfc3b3 100644
--- a/drivers/net/ethernet/microchip/lan743x_main.c
+++ b/drivers/net/ethernet/microchip/lan743x_main.c
@@ -9,9 +9,12 @@
 #include <linux/microchipphy.h>
 #include <linux/net_tstamp.h>
 #include <linux/phy.h>
+#include <linux/phy_fixed.h>
 #include <linux/rtnetlink.h>
 #include <linux/iopoll.h>
 #include <linux/crc16.h>
+#include <linux/of_mdio.h>
+#include <linux/of_net.h>
 #include "lan743x_main.h"
 #include "lan743x_ethtool.h"
 
@@ -946,6 +949,9 @@ static void lan743x_phy_link_status_change(struct 
net_device *netdev)
 {
        struct lan743x_adapter *adapter = netdev_priv(netdev);
        struct phy_device *phydev = netdev->phydev;
+       struct device_node *phynode;
+       phy_interface_t phyifc = PHY_INTERFACE_MODE_GMII;
+       u32 data;
 
        phy_print_status(phydev);
        if (phydev->state == PHY_RUNNING) {
@@ -953,6 +959,48 @@ static void lan743x_phy_link_status_change(struct 
net_device *netdev)
                int remote_advertisement = 0;
                int local_advertisement = 0;
 
+               /* check if a fixed-link is defined in device-tree */
+               phynode = of_node_get(adapter->pdev->dev.of_node);
+               if (phynode && of_phy_is_fixed_link(phynode)) {
+                       /* Configure MAC to fixed link parameters */
+                       data = lan743x_csr_read(adapter, MAC_CR);
+                       /* Disable auto negotiation */
+                       data &= ~(MAC_CR_ADD_ | MAC_CR_ASD_);
+                       /* Set duplex mode */
+                       if (phydev->duplex)
+                               data |= MAC_CR_DPX_;
+                       else
+                               data &= ~MAC_CR_DPX_;
+                       /* Set bus speed */
+                       switch (phydev->speed) {
+                       case 10:
+                               data &= ~MAC_CR_CFG_H_;
+                               data &= ~MAC_CR_CFG_L_;
+                               break;
+                       case 100:
+                               data &= ~MAC_CR_CFG_H_;
+                               data |= MAC_CR_CFG_L_;
+                               break;
+                       case 1000:
+                               data |= MAC_CR_CFG_H_;
+                               data |= MAC_CR_CFG_L_;
+                               break;
+                       }
+                       /* Set interface mode */
+                       of_get_phy_mode(phynode, &phyifc);
+                       if (phyifc == PHY_INTERFACE_MODE_RGMII ||
+                           phyifc == PHY_INTERFACE_MODE_RGMII_ID ||
+                           phyifc == PHY_INTERFACE_MODE_RGMII_RXID ||
+                           phyifc == PHY_INTERFACE_MODE_RGMII_TXID)
+                               /* RGMII */
+                               data &= ~MAC_CR_MII_EN_;
+                       else
+                               /* GMII */
+                               data |= MAC_CR_MII_EN_;
+                       lan743x_csr_write(adapter, MAC_CR, data);
+               }
+               of_node_put(phynode);
+
                memset(&ksettings, 0, sizeof(ksettings));
                phy_ethtool_get_link_ksettings(netdev, &ksettings);
                local_advertisement =
@@ -974,6 +1022,8 @@ static void lan743x_phy_close(struct lan743x_adapter 
*adapter)
 
        phy_stop(netdev->phydev);
        phy_disconnect(netdev->phydev);
+       if (of_phy_is_fixed_link(adapter->pdev->dev.of_node))
+               of_phy_deregister_fixed_link(adapter->pdev->dev.of_node);
        netdev->phydev = NULL;
 }
 
@@ -982,18 +1032,44 @@ static int lan743x_phy_open(struct lan743x_adapter 
*adapter)
        struct lan743x_phy *phy = &adapter->phy;
        struct phy_device *phydev;
        struct net_device *netdev;
+       struct device_node *phynode = NULL;
+       phy_interface_t phyifc = PHY_INTERFACE_MODE_GMII;
        int ret = -EIO;
 
        netdev = adapter->netdev;
-       phydev = phy_find_first(adapter->mdiobus);
-       if (!phydev)
-               goto return_error;
 
-       ret = phy_connect_direct(netdev, phydev,
-                                lan743x_phy_link_status_change,
-                                PHY_INTERFACE_MODE_GMII);
-       if (ret)
-               goto return_error;
+       /* check if a fixed-link is defined in device-tree */
+       phynode = of_node_get(adapter->pdev->dev.of_node);
+       if (phynode && of_phy_is_fixed_link(phynode)) {
+               netdev_dbg(netdev, "fixed-link detected\n");
+
+               ret = of_phy_register_fixed_link(phynode);
+               if (ret) {
+                       netdev_err(netdev, "cannot register fixed PHY\n");
+                       goto return_error;
+               }
+
+               of_get_phy_mode(phynode, &phyifc);
+               phydev = of_phy_connect(netdev, phynode,
+                                       lan743x_phy_link_status_change,
+                                       0, phyifc);
+               if (!phydev)
+                       goto return_error;
+       } else {
+               phydev = phy_find_first(adapter->mdiobus);
+               if (!phydev)
+                       goto return_error;
+
+               ret = phy_connect_direct(netdev, phydev,
+                                        lan743x_phy_link_status_change,
+                                        PHY_INTERFACE_MODE_GMII);
+               /* Note: We cannot use phyifc here because this would be SGMII
+                * on a standard PC.
+                */
+               if (ret)
+                       goto return_error;
+       }
+       of_node_put(phynode);
 
        /* MAC doesn't support 1000T Half */
        phy_remove_link_mode(phydev, ETHTOOL_LINK_MODE_1000baseT_Half_BIT);
@@ -1008,6 +1084,7 @@ static int lan743x_phy_open(struct lan743x_adapter 
*adapter)
        return 0;
 
 return_error:
+       of_node_put(phynode);
        return ret;
 }
 
diff --git a/drivers/net/ethernet/microchip/lan743x_main.h 
b/drivers/net/ethernet/microchip/lan743x_main.h
index 3b02eeae5f45..e49f6b6cd440 100644
--- a/drivers/net/ethernet/microchip/lan743x_main.h
+++ b/drivers/net/ethernet/microchip/lan743x_main.h
@@ -104,10 +104,14 @@
        ((value << 0) & FCT_FLOW_CTL_ON_THRESHOLD_)
 
 #define MAC_CR                         (0x100)
+#define MAC_CR_MII_EN_                 BIT(19)
 #define MAC_CR_EEE_EN_                 BIT(17)
 #define MAC_CR_ADD_                    BIT(12)
 #define MAC_CR_ASD_                    BIT(11)
 #define MAC_CR_CNTR_RST_               BIT(5)
+#define MAC_CR_DPX_                    BIT(3)
+#define MAC_CR_CFG_H_                  BIT(2)
+#define MAC_CR_CFG_L_                  BIT(1)
 #define MAC_CR_RST_                    BIT(0)
 
 #define MAC_RX                         (0x104)
-- 
2.20.1

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