net: stmmac: dwmac-starfive: Add phy interface settings

dwmac supports multiple modess. When working under rmii and rgmii,
you need to set different phy interfaces.

According to the dwmac document, when working in rmii, it needs to be
set to 0x4, and rgmii needs to be set to 0x1.

The phy interface needs to be set in syscon, the format is as follows:
starfive,syscon: <&syscon, offset, shift>
Tested-by: Tommaso Merciai <tomm.merciai@gmail.com>
Signed-off-by: Samin Guo <samin.guo@starfivetech.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

drivers/net/ethernet/stmicro/stmmac/dwmac-starfive.c

@@ -13,6 +13,10 @@
 
 #include "stmmac_platform.h"
 
+#define STARFIVE_DWMAC_PHY_INFT_RGMII	0x1
+#define STARFIVE_DWMAC_PHY_INFT_RMII	0x4
+#define STARFIVE_DWMAC_PHY_INFT_FIELD	0x7U
+
 struct starfive_dwmac {
 	struct device *dev;
 	struct clk *clk_tx;
@@ -46,6 +50,46 @@ static void starfive_dwmac_fix_mac_speed(void *priv, unsigned int speed)
 		dev_err(dwmac->dev, "failed to set tx rate %lu\n", rate);
 }
 
+static int starfive_dwmac_set_mode(struct plat_stmmacenet_data *plat_dat)
+{
+	struct starfive_dwmac *dwmac = plat_dat->bsp_priv;
+	struct regmap *regmap;
+	unsigned int args[2];
+	unsigned int mode;
+	int err;
+
+	switch (plat_dat->interface) {
+	case PHY_INTERFACE_MODE_RMII:
+		mode = STARFIVE_DWMAC_PHY_INFT_RMII;
+		break;
+
+	case PHY_INTERFACE_MODE_RGMII:
+	case PHY_INTERFACE_MODE_RGMII_ID:
+		mode = STARFIVE_DWMAC_PHY_INFT_RGMII;
+		break;
+
+	default:
+		dev_err(dwmac->dev, "unsupported interface %d\n",
+			plat_dat->interface);
+		return -EINVAL;
+	}
+
+	regmap = syscon_regmap_lookup_by_phandle_args(dwmac->dev->of_node,
+						      "starfive,syscon",
+						      2, args);
+	if (IS_ERR(regmap))
+		return dev_err_probe(dwmac->dev, PTR_ERR(regmap), "getting the regmap failed\n");
+
+	/* args[0]:offset  args[1]: shift */
+	err = regmap_update_bits(regmap, args[0],
+				 STARFIVE_DWMAC_PHY_INFT_FIELD << args[1],
+				 mode << args[1]);
+	if (err)
+		return dev_err_probe(dwmac->dev, err, "error setting phy mode\n");
+
+	return 0;
+}
+
 static int starfive_dwmac_probe(struct platform_device *pdev)
 {
 	struct plat_stmmacenet_data *plat_dat;
@@ -91,6 +135,10 @@ static int starfive_dwmac_probe(struct platform_device *pdev)
 	plat_dat->bsp_priv = dwmac;
 	plat_dat->dma_cfg->dche = true;
 
+	err = starfive_dwmac_set_mode(plat_dat);
+	if (err)
+		return err;
+
 	err = stmmac_dvr_probe(&pdev->dev, plat_dat, &stmmac_res);
 	if (err) {
 		stmmac_remove_config_dt(pdev, plat_dat);