CODEWITHSUNDEEP
linuxlinux-kerneldriverethernet
rabi
rabi

Reputation: 11

How to activate phyless linux Ethernet driver

I was trying to activate Linux phyless Ethernet driver. There are no much information on net. I am using ARM based Linux kernel SOC is connected to a 1GBPS RGMII port back to back without having a real PHY. Came to know Linux has fixed phy support. Some of the files have used fixed_phy_add function. But still not getting clear idea how to activate. Any kind of help or pointer will really help here.

Upvotes: 1

Views: 4537

Answers (1)

slobobaby
slobobaby

Reputation: 706

Yeah. I have just done this for our board. What really confused me was that you need to add the fixed phy before the fixed mdio bus is activated. So either you need to add it early in your platform init code or hack it into the fixed mdio code like I did (just to get things working, of course). This patch did it for me.

diff --git a/drivers/net/phy/fixed.c b/drivers/net/phy/fixed.c
index ba55adf..7013ef0 100644
--- a/drivers/net/phy/fixed.c
+++ b/drivers/net/phy/fixed.c
@@ -203,11 +203,24 @@ err_regs:
 }
 EXPORT_SYMBOL_GPL(fixed_phy_add);

+static struct fixed_phy_status fixed_phy_status = {
+       .link           = 1,
+       .speed          = 100,
+       .duplex         = 0,
+};
+
 static int __init fixed_mdio_bus_init(void)
 {
        struct fixed_mdio_bus *fmb = &platform_fmb;
        int ret;

+       ret = fixed_phy_add(PHY_POLL, 0, &fixed_phy_status);
+        if (ret < 0)
+        {
+            pr_err("could not add fixed phy.\n");
+            return ret;
+        }
+
        pdev = platform_device_register_simple("Fixed MDIO bus", 0, NULL, 0);
        if (IS_ERR(pdev)) {
                ret = PTR_ERR(pdev);

The next step is to use this phy in your driver, it should be enough to use the name fixed-0:00 as the phy name when you look it up (the :00 is the fixed phy id 0 in the fixed_phy_add above) 

snprintf(phy_id, sizeof(slave_data->phy_id), PHY_ID_FMT, "fixed-0", 0);

Then the phy_connect your driver already has should find the fixed phy and it should work as long as the fixed configuration matches the other side (a switch in our case):

phy_connect(ndev, phy_id, &_adjust_link, phy_if);

There should be a method to make all this work with device tree too but no-one has gotten there yet, AFAICS.

Good Luck.

Upvotes: 3

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