PCI/pwrctrl: Move creation of pwrctrl devices to pci_scan_device()

Current way of creating pwrctrl devices requires iterating through the
child devicetree nodes of the PCI bridge in pci_pwrctrl_create_devices().
Even though it works, it creates confusion as there is no symmetry between
this and pci_pwrctrl_unregister() function that removes the pwrctrl
devices.

So to make these two functions symmetric, move the creation of pwrctrl
devices to pci_scan_device(). During the scan of each device in a slot,
the devicetree node (if exists) for the PCI device will be checked. If it
has the supplies populated, then the pwrctrl device will be created.

Since the PCI device scan happens so early, there would be no "struct
pci_dev" available for the device. So the host bridge is used as the
parent of all pwrctrl devices.

One nice side effect of this move is that, it is now possible to have
pwrctrl devices for PCI bridges as well (to control the supplies of PCI
slots).

Suggested-by: Lukas Wunner <lukas@wunner.de>
Tested-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Link: https://lore.kernel.org/r/20250116-pci-pwrctrl-slot-v3-1-827473c8fbf4@linaro.org
[kwilczynski: commit log]
Signed-off-by: Krzysztof Wilczyński <kwilczynski@kernel.org>

3 files changed, 35 insertions, 44 deletions

diff --git a/drivers/pci/bus.c b/drivers/pci/bus.c
index 98910bc0fcc4..b6851101ac36 100644
--- a/drivers/pci/bus.c
+++ b/drivers/pci/bus.c
@@ -331,47 +331,6 @@ void __weak pcibios_resource_survey_bus(struct pci_bus *bus) { }
 
 void __weak pcibios_bus_add_device(struct pci_dev *pdev) { }
 
-/*
- * Create pwrctrl devices (if required) for the PCI devices to handle the power
- * state.
- */
-static void pci_pwrctrl_create_devices(struct pci_dev *dev)
-{
-	struct device_node *np = dev_of_node(&dev->dev);
-	struct device *parent = &dev->dev;
-	struct platform_device *pdev;
-
-	/*
-	 * First ensure that we are starting from a PCI bridge and it has a
-	 * corresponding devicetree node.
-	 */
-	if (np && pci_is_bridge(dev)) {
-		/*
-		 * Now look for the child PCI device nodes and create pwrctrl
-		 * devices for them. The pwrctrl device drivers will manage the
-		 * power state of the devices.
-		 */
-		for_each_available_child_of_node_scoped(np, child) {
-			/*
-			 * First check whether the pwrctrl device really
-			 * needs to be created or not. This is decided
-			 * based on at least one of the power supplies
-			 * being defined in the devicetree node of the
-			 * device.
-			 */
-			if (!of_pci_supply_present(child)) {
-				pci_dbg(dev, "skipping OF node: %s\n", child->name);
-				return;
-			}
-
-			/* Now create the pwrctrl device */
-			pdev = of_platform_device_create(child, NULL, parent);
-			if (!pdev)
-				pci_err(dev, "failed to create OF node: %s\n", child->name);
-		}
-	}
-}
-
 /**
  * pci_bus_add_device - start driver for a single device
  * @dev: device to add
@@ -396,8 +355,6 @@ void pci_bus_add_device(struct pci_dev *dev)
 	pci_proc_attach_device(dev);
 	pci_bridge_d3_update(dev);
 
-	pci_pwrctrl_create_devices(dev);
-
 	/*
 	 * If the PCI device is associated with a pwrctrl device with a
 	 * power supply, create a device link between the PCI device and
diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index b6536ed599c3..95a91778bb5d 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -9,6 +9,8 @@
 #include <linux/pci.h>
 #include <linux/msi.h>
 #include <linux/of_pci.h>
+#include <linux/of_platform.h>
+#include <linux/platform_device.h>
 #include <linux/pci_hotplug.h>
 #include <linux/slab.h>
 #include <linux/module.h>
@@ -2494,6 +2496,36 @@ bool pci_bus_read_dev_vendor_id(struct pci_bus *bus, int devfn, u32 *l,
 EXPORT_SYMBOL(pci_bus_read_dev_vendor_id);
 
 /*
+ * Create pwrctrl device (if required) for the PCI device to handle the power
+ * state.
+ */
+static void pci_pwrctrl_create_device(struct pci_bus *bus, int devfn)
+{
+	struct pci_host_bridge *host = pci_find_host_bridge(bus);
+	struct platform_device *pdev;
+	struct device_node *np;
+
+	np = of_pci_find_child_device(dev_of_node(&bus->dev), devfn);
+	if (!np || of_find_device_by_node(np))
+		return;
+
+	/*
+	 * First check whether the pwrctrl device really needs to be created or
+	 * not. This is decided based on at least one of the power supplies
+	 * being defined in the devicetree node of the device.
+	 */
+	if (!of_pci_supply_present(np)) {
+		pr_debug("PCI/pwrctrl: Skipping OF node: %s\n", np->name);
+		return;
+	}
+
+	/* Now create the pwrctrl device */
+	pdev = of_platform_device_create(np, NULL, &host->dev);
+	if (!pdev)
+		pr_err("PCI/pwrctrl: Failed to create pwrctrl device for OF node: %s\n", np->name);
+}
+
+/*
  * Read the config data for a PCI device, sanity-check it,
  * and fill in the dev structure.
  */
@@ -2502,6 +2534,8 @@ static struct pci_dev *pci_scan_device(struct pci_bus *bus, int devfn)
 	struct pci_dev *dev;
 	u32 l;
 
+	pci_pwrctrl_create_device(bus, devfn);
+
 	if (!pci_bus_read_dev_vendor_id(bus, devfn, &l, 60*1000))
 		return NULL;
 
diff --git a/drivers/pci/pwrctrl/core.c b/drivers/pci/pwrctrl/core.c
index 2fb174db91e5..9cc7e2b7f2b5 100644
--- a/drivers/pci/pwrctrl/core.c
+++ b/drivers/pci/pwrctrl/core.c
@@ -44,7 +44,7 @@ static void rescan_work_func(struct work_struct *work)
 						   struct pci_pwrctrl, work);
 
 	pci_lock_rescan_remove();
-	pci_rescan_bus(to_pci_dev(pwrctrl->dev->parent)->bus);
+	pci_rescan_bus(to_pci_host_bridge(pwrctrl->dev->parent)->bus);
 	pci_unlock_rescan_remove();
 }