PCI: brcmstb: Add mechanism to turn on subdev regulators

jim2101024 · bjorn-helgaas · commit 67211aadcb4b · 2022-01-12T13:45:50.000-06:00
Add a mechanism to identify standard PCIe regulators in the DT, allocate them, and turn them on before the rest of the bus is scanned during pci_host_probe(). The allocated structure that contains the regulators is stored in the port driver dev.driver_data field. Here is a point-by-point of how and when this mechanism is activated: If: -- PCIe RC driver sets pci_ops {add,remove)_bus to pci_subdev_regulators_{add,remove}_bus during its probe. -- There is a DT node "RB" under the host bridge DT node. -- During the RC driver's pci_host_probe() the add_bus callback is invoked where (bus->parent && pci_is_root_bus(bus->parent) is true Then: -- A struct subdev_regulators structure will be allocated and assigned to bus->dev.driver_data. -- regulator_bulk_{get,enable} will be invoked on &bus->dev and the former will search for and process any vpcie{12v,3v3,3v3aux}-supply properties that reside in node "RB". -- The regulators will be turned off/on for any unbind/bind operations. -- The regulators will be turned off/on for any suspend/resumes, but only if the RC driver handles this on its own. This will appear in a later commit for the pcie-brcmstb.c driver. The unabridged reason for doing this is as follows. We would like the Broadcom STB PCIe root complex driver (and others) to be able to turn off/on regulators[1] that provide power to endpoint[2] devices. Typically, the drivers of these endpoint devices are stock Linux drivers that are not aware that these regulator(s) exist and must be turned on for the driver to be probed. The simple solution of course is to turn these regulators on at boot and keep them on. However, this solution does not satisfy at least three of our usage modes: 1. For example, one customer uses multiple PCIe controllers, but wants the ability to, by script invoking and unbind, turn any or all of them and their subdevices off to save power, e.g. when in battery mode. 2. Another example is when a watchdog script discovers that an endpoint device is in an unresponsive state and would like to unbind, power toggle, and re-bind just the PCIe endpoint and controller. 3. Of course we also want power turned off during suspend mode. However, some endpoint devices may be able to "wake" during suspend and we need to recognise this case and veto the nominal act of turning off its regulator. Such is the case with Wake-on-LAN and Wake-on-WLAN support where the PCIe endpoint device needs to be kept powered on in order to receive network packets and wake the system. In all of these cases it is advantageous for the PCIe controller to govern the turning off/on the regulators needed by the endpoint device. The first two cases can be done by simply unbinding and binding the PCIe controller, if the controller has control of these regulators. [1] These regulators typically govern the actual power supply to the endpoint chip. Sometimes they may be the official PCIe socket power -- such as 3.3v or aux-3.3v. Sometimes they are truly the regulator(s) that supply power to the EP chip. [2] The 99% configuration of our boards is a single endpoint device attached to the PCIe controller. I use the term endpoint but it could possibly mean a switch as well. Link: https://lore.kernel.org/r/20220106160332.2143-6-jim2101024@gmail.com Signed-off-by: Jim Quinlan <jim2101024@gmail.com> Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com> Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
diff --git a/drivers/pci/controller/pcie-brcmstb.c b/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>
@@ -260,6 +261,14 @@ static const struct pcie_cfg_data bcm2711_cfg = {
 	.bridge_sw_init_set = brcm_pcie_bridge_sw_init_set_generic,
 };
 
+struct subdev_regulators {
+	unsigned int num_supplies;
+	struct regulator_bulk_data supplies[];
+};
+
+static int pci_subdev_regulators_add_bus(struct pci_bus *bus);
+static void pci_subdev_regulators_remove_bus(struct pci_bus *bus);
+
 struct brcm_msi {
 	struct device		*dev;
 	void __iomem		*base;
@@ -408,6 +417,71 @@ static int brcm_pcie_set_ssc(struct brcm_pcie *pcie)
 	return ssc && pll ? 0 : -EIO;
 }
 
+static void *alloc_subdev_regulators(struct device *dev)
+{
+	static const char * const supplies[] = {
+		"vpcie3v3",
+		"vpcie3v3aux",
+		"vpcie12v",
+	};
+	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 pci_subdev_regulators_add_bus(struct pci_bus *bus)
+{
+	struct device *dev = &bus->dev;
+	struct subdev_regulators *sr;
+	int ret;
+
+	if (!dev->of_node || !bus->parent || !pci_is_root_bus(bus->parent))
+		return 0;
+
+	if (dev->driver_data)
+		dev_err(dev, "dev.driver_data unexpectedly non-NULL\n");
+
+	sr = alloc_subdev_regulators(dev);
+	if (!sr)
+		return -ENOMEM;
+
+	dev->driver_data = sr;
+	ret = regulator_bulk_get(dev, sr->num_supplies, sr->supplies);
+	if (ret)
+		return ret;
+
+	ret = regulator_bulk_enable(sr->num_supplies, sr->supplies);
+	if (ret) {
+		dev_err(dev, "failed to enable regulators for downstream device\n");
+		return ret;
+	}
+
+	return 0;
+}
+
+static void pci_subdev_regulators_remove_bus(struct pci_bus *bus)
+{
+	struct device *dev = &bus->dev;
+	struct subdev_regulators *sr = dev->driver_data;
+
+	if (!sr || !bus->parent || !pci_is_root_bus(bus->parent))
+		return;
+
+	if (regulator_bulk_disable(sr->num_supplies, sr->supplies))
+		dev_err(dev, "failed to disable regulators for downstream device\n");
+	dev->driver_data = NULL;
+}
+
 /* Limits operation to a specific generation (1, 2, or 3) */
 static void brcm_pcie_set_gen(struct brcm_pcie *pcie, int gen)
 {
@@ -731,6 +805,8 @@ 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 = pci_subdev_regulators_add_bus,
+	.remove_bus = pci_subdev_regulators_remove_bus,
 };
 
 static inline void brcm_pcie_bridge_sw_init_set_generic(struct brcm_pcie *pcie, u32 val)
