PCI: starfive: Use regulator APIs to control the 3v3 power supply of PCIe slots

The driver has been using the "enable-gpios" property to control the 3v3
power supply of PCIe slots. But it is not documented in the dt-bindings and
also using GPIO APIs is not a standard way to control PCIe slot power, so
use the documented "vpcie3v3-supply" property and regulator APIs to control
the slot supply.

This change will break the DTs which used "enable-gpio" or "enable-gpios"
property under the controller node. Since these properties were not defined
in the bindings, it is safe to switch to "vpcie3v3-supply". Any out-of-tree
DTS impacted by this change should migrate to "vpcie3v3-supply" instead.

Signed-off-by: Hal Feng <hal.feng@starfivetech.com>
[mani: reworded description]
Signed-off-by: Manivannan Sadhasivam <mani@kernel.org>
Acked-by: Kevin Xie <kevin.xie@starfivetech.com>
Link: https://patch.msgid.link/20251218102149.28062-1-hal.feng@starfivetech.com

Author: hal-feng

drivers/pci/controller/plda/pcie-starfive.c

@@ -55,7 +55,7 @@ struct starfive_jh7110_pcie {
 	struct reset_control *resets;
 	struct clk_bulk_data *clks;
 	struct regmap *reg_syscon;
-	struct gpio_desc *power_gpio;
+	struct regulator *vpcie3v3;
 	struct gpio_desc *reset_gpio;
 	struct phy *phy;
 
@@ -153,11 +153,13 @@ static int starfive_pcie_parse_dt(struct starfive_jh7110_pcie *pcie,
 		return dev_err_probe(dev, PTR_ERR(pcie->reset_gpio),
 				     "failed to get perst-gpio\n");
 
-	pcie->power_gpio = devm_gpiod_get_optional(dev, "enable",
-						   GPIOD_OUT_LOW);
-	if (IS_ERR(pcie->power_gpio))
-		return dev_err_probe(dev, PTR_ERR(pcie->power_gpio),
-				     "failed to get power-gpio\n");
+	pcie->vpcie3v3 = devm_regulator_get_optional(dev, "vpcie3v3");
+	if (IS_ERR(pcie->vpcie3v3)) {
+		if (PTR_ERR(pcie->vpcie3v3) != -ENODEV)
+			return dev_err_probe(dev, PTR_ERR(pcie->vpcie3v3),
+					     "failed to get vpcie3v3 regulator\n");
+		pcie->vpcie3v3 = NULL;
+	}
 
 	return 0;
 }
@@ -270,8 +272,8 @@ static void starfive_pcie_host_deinit(struct plda_pcie_rp *plda)
 		container_of(plda, struct starfive_jh7110_pcie, plda);
 
 	starfive_pcie_clk_rst_deinit(pcie);
-	if (pcie->power_gpio)
-		gpiod_set_value_cansleep(pcie->power_gpio, 0);
+	if (pcie->vpcie3v3)
+		regulator_disable(pcie->vpcie3v3);
 	starfive_pcie_disable_phy(pcie);
 }
 
@@ -304,8 +306,11 @@ static int starfive_pcie_host_init(struct plda_pcie_rp *plda)
 	if (ret)
 		return ret;
 
-	if (pcie->power_gpio)
-		gpiod_set_value_cansleep(pcie->power_gpio, 1);
+	if (pcie->vpcie3v3) {
+		ret = regulator_enable(pcie->vpcie3v3);
+		if (ret)
+			dev_err_probe(dev, ret, "failed to enable vpcie3v3 regulator\n");
+	}
 
 	if (pcie->reset_gpio)
 		gpiod_set_value_cansleep(pcie->reset_gpio, 1);