net: stmmac: dwmac-rk: Validate GRF and peripheral GRF during probe

All Rockchip GMAC variants typically write to GRF regs to control e.g.
interface mode, speed and MAC rx/tx delay. Newer SoCs such as RK3576 and
RK3588 use a mix of GRF and peripheral GRF regs. These syscon regmaps is
located with help of a rockchip,grf and rockchip,php-grf phandle.

However, validating the rockchip,grf and rockchip,php-grf syscon regmap
is deferred until e.g. interface mode or speed is configured, inside the
individual SoC specific operations.

Change to validate the rockchip,grf and rockchip,php-grf syscon regmap
at probe time to simplify all SoC specific operations.

This should not introduce any backward compatibility issues as all
GMAC nodes have been added together with a rockchip,grf phandle (and
rockchip,php-grf where required) in their initial commit.

Signed-off-by: Jonas Karlman <jonas@kwiboo.se>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://patch.msgid.link/20250308213720.2517944-3-jonas@kwiboo.se
Reviewed-by: Sebastian Reichel <sebastian.reichel@collabora.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

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

@@ -33,6 +33,7 @@ struct rk_gmac_ops {
 	void (*set_clock_selection)(struct rk_priv_data *bsp_priv, bool input,
 				    bool enable);
 	void (*integrated_phy_powerup)(struct rk_priv_data *bsp_priv);
+	bool php_grf_required;
 	bool regs_valid;
 	u32 regs[];
 };
@@ -1254,6 +1255,7 @@ static const struct rk_gmac_ops rk3576_ops = {
 	.set_rgmii_speed = rk3576_set_gmac_speed,
 	.set_rmii_speed = rk3576_set_gmac_speed,
 	.set_clock_selection = rk3576_set_clock_selection,
+	.php_grf_required = true,
 	.regs_valid = true,
 	.regs = {
 		0x2a220000, /* gmac0 */
@@ -1401,6 +1403,7 @@ static const struct rk_gmac_ops rk3588_ops = {
 	.set_rgmii_speed = rk3588_set_gmac_speed,
 	.set_rmii_speed = rk3588_set_gmac_speed,
 	.set_clock_selection = rk3588_set_clock_selection,
+	.php_grf_required = true,
 	.regs_valid = true,
 	.regs = {
 		0xfe1b0000, /* gmac0 */
@@ -1812,8 +1815,22 @@ static struct rk_priv_data *rk_gmac_setup(struct platform_device *pdev,
 
 	bsp_priv->grf = syscon_regmap_lookup_by_phandle(dev->of_node,
 							"rockchip,grf");
-	bsp_priv->php_grf = syscon_regmap_lookup_by_phandle(dev->of_node,
-							    "rockchip,php-grf");
+	if (IS_ERR(bsp_priv->grf)) {
+		dev_err_probe(dev, PTR_ERR(bsp_priv->grf),
+			      "failed to lookup rockchip,grf\n");
+		return ERR_CAST(bsp_priv->grf);
+	}
+
+	if (ops->php_grf_required) {
+		bsp_priv->php_grf =
+			syscon_regmap_lookup_by_phandle(dev->of_node,
+							"rockchip,php-grf");
+		if (IS_ERR(bsp_priv->php_grf)) {
+			dev_err_probe(dev, PTR_ERR(bsp_priv->php_grf),
+				      "failed to lookup rockchip,php-grf\n");
+			return ERR_CAST(bsp_priv->php_grf);
+		}
+	}
 
 	if (plat->phy_node) {
 		bsp_priv->integrated_phy = of_property_read_bool(plat->phy_node,