PCI: brcmstb: Enable child bus device regulators from DT

Some platforms have power regulators for slots or devices below Root Ports.
On platforms like Raspberry Pi 4, these regulators are described in the
Root Port device tree node, since they logically belong to the Root Port,
not to the host bridge itself.

Add an .add_bus() hook (called when pci_alloc_child_bus() allocates the
secondary ("child") bus for a bridge), and look for such regulators.  If we
find some, enable them before bringing up the link and enumerating devices
on the child bus.

Similarly, when pci_remove_bus() calls the ops->remove_bus() hook, disable
the regulators.

The regulators that may be described in a Root Port DT device are:

  vpcie3v3
  vpcie3v3aux
  vpcie12v

These control power to the device downstream from the Root Port.

[bhelgaas: commit log, name hooks brcm_pcie_add_bus(), etc, since we only
support one set of subregulator info, save info in struct brcm_pcie instead
of dev->driver_data, move brcm_pcie_start_link() from probe to .add_bus()
(from subsequent patch)]
Link: https://lore.kernel.org/r/20220725151258.42574-5-jim2101024@gmail.com
Signed-off-by: Jim Quinlan <jim2101024@gmail.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Tested-by: Florian Fainelli <f.fainelli@gmail.com>

drivers/pci/controller/pcie-brcmstb.c

@@ -24,6 +24,7 @@
 #include <linux/pci.h>
 #include <linux/pci-ecam.h>
 #include <linux/printk.h>
+#include <linux/regulator/consumer.h>
 #include <linux/reset.h>
 #include <linux/sizes.h>
 #include <linux/slab.h>
@@ -218,6 +219,11 @@ struct pcie_cfg_data {
 	void (*bridge_sw_init_set)(struct brcm_pcie *pcie, u32 val);
 };
 
+struct subdev_regulators {
+	unsigned int num_supplies;
+	struct regulator_bulk_data supplies[];
+};
+
 struct brcm_msi {
 	struct device		*dev;
 	void __iomem		*base;
@@ -255,6 +261,7 @@ struct brcm_pcie {
 	u32			hw_rev;
 	void			(*perst_set)(struct brcm_pcie *pcie, u32 val);
 	void			(*bridge_sw_init_set)(struct brcm_pcie *pcie, u32 val);
+	struct subdev_regulators *sr;
 };
 
 static inline bool is_bmips(const struct brcm_pcie *pcie)
@@ -1065,6 +1072,82 @@ static int brcm_pcie_start_link(struct brcm_pcie *pcie)
 	return 0;
 }
 
+static const char * const supplies[] = {
+	"vpcie3v3",
+	"vpcie3v3aux",
+	"vpcie12v",
+};
+
+static void *alloc_subdev_regulators(struct device *dev)
+{
+	const size_t size = sizeof(struct subdev_regulators) +
+		sizeof(struct regulator_bulk_data) * ARRAY_SIZE(supplies);
+	struct subdev_regulators *sr;
+	int i;
+
+	sr = devm_kzalloc(dev, size, GFP_KERNEL);
+	if (sr) {
+		sr->num_supplies = ARRAY_SIZE(supplies);
+		for (i = 0; i < ARRAY_SIZE(supplies); i++)
+			sr->supplies[i].supply = supplies[i];
+	}
+
+	return sr;
+}
+
+static int brcm_pcie_add_bus(struct pci_bus *bus)
+{
+	struct brcm_pcie *pcie = bus->sysdata;
+	struct device *dev = &bus->dev;
+	struct subdev_regulators *sr;
+	int ret;
+
+	if (!bus->parent || !pci_is_root_bus(bus->parent))
+		return 0;
+
+	if (dev->of_node) {
+		sr = alloc_subdev_regulators(dev);
+		if (!sr) {
+			dev_info(dev, "Can't allocate regulators for downstream device\n");
+			goto no_regulators;
+		}
+
+		pcie->sr = sr;
+
+		ret = regulator_bulk_get(dev, sr->num_supplies, sr->supplies);
+		if (ret) {
+			dev_info(dev, "No regulators for downstream device\n");
+			goto no_regulators;
+		}
+
+		ret = regulator_bulk_enable(sr->num_supplies, sr->supplies);
+		if (ret) {
+			dev_err(dev, "Can't enable regulators for downstream device\n");
+			regulator_bulk_free(sr->num_supplies, sr->supplies);
+			pcie->sr = NULL;
+		}
+	}
+
+no_regulators:
+	brcm_pcie_start_link(pcie);
+	return 0;
+}
+
+static void brcm_pcie_remove_bus(struct pci_bus *bus)
+{
+	struct brcm_pcie *pcie = bus->sysdata;
+	struct subdev_regulators *sr = pcie->sr;
+	struct device *dev = &bus->dev;
+
+	if (!sr)
+		return;
+
+	if (regulator_bulk_disable(sr->num_supplies, sr->supplies))
+		dev_err(dev, "Failed to disable regulators for downstream device\n");
+	regulator_bulk_free(sr->num_supplies, sr->supplies);
+	pcie->sr = NULL;
+}
+
 /* L23 is a low-power PCIe link state */
 static void brcm_pcie_enter_l23(struct brcm_pcie *pcie)
 {
@@ -1336,12 +1419,16 @@ static struct pci_ops brcm_pcie_ops = {
 	.map_bus = brcm_pcie_map_conf,
 	.read = pci_generic_config_read,
 	.write = pci_generic_config_write,
+	.add_bus = brcm_pcie_add_bus,
+	.remove_bus = brcm_pcie_remove_bus,
 };
 
 static struct pci_ops brcm_pcie_ops32 = {
 	.map_bus = brcm_pcie_map_conf32,
 	.read = pci_generic_config_read32,
 	.write = pci_generic_config_write32,
+	.add_bus = brcm_pcie_add_bus,
+	.remove_bus = brcm_pcie_remove_bus,
 };
 
 static int brcm_pcie_probe(struct platform_device *pdev)
@@ -1414,10 +1501,6 @@ static int brcm_pcie_probe(struct platform_device *pdev)
 	if (ret)
 		goto fail;
 
-	ret = brcm_pcie_start_link(pcie);
-	if (ret)
-		goto fail;
-
 	pcie->hw_rev = readl(pcie->base + PCIE_MISC_REVISION);
 	if (pcie->type == BCM4908 && pcie->hw_rev >= BRCM_PCIE_HW_REV_3_20) {
 		dev_err(pcie->dev, "hardware revision with unsupported PERST# setup\n");
@@ -1439,7 +1522,17 @@ static int brcm_pcie_probe(struct platform_device *pdev)
 
 	platform_set_drvdata(pdev, pcie);
 
-	return pci_host_probe(bridge);
+	ret = pci_host_probe(bridge);
+	if (!ret && !brcm_pcie_link_up(pcie))
+		ret = -ENODEV;
+
+	if (ret) {
+		brcm_pcie_remove(pdev);
+		return ret;
+	}
+
+	return 0;
+
 fail:
 	__brcm_pcie_remove(pcie);
 	return ret;