PCI/pwrctrl: Add pwrctrl driver for PCI slots

This driver is used to control the power state of the devices attached to
the PCI slots. Currently, it controls the voltage rails of the PCI slots
defined in the devicetree node of the root port.

The voltage rails for PCI slots are documented in the DT-schema:

  https://github.com/devicetree-org/dt-schema/blob/v2024.11/dtschema/schemas/pci/pci-bus-common.yaml#L153

Since this driver has to work with different kind of slots (PCIe
x1/x4/x8/x16, Mini PCIe, PCI, etc.), the driver is thus using the
of_regulator_bulk_get_all() API to obtain the voltage regulators defined
in the DT node, instead of hardcoding them.

As such, the DT node of the root port should define the relevant supply
properties corresponding to the voltage rails of the PCI slot.

Tested-by: Bartosz Golaszewski <[email protected]>
Signed-off-by: Manivannan Sadhasivam <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
[kwilczynski: commit log]
Signed-off-by: Krzysztof Wilczyński <[email protected]>

Author: Mani-Sadhasivam

drivers/pci/pwrctrl/Kconfig

@@ -10,3 +10,14 @@ config PCI_PWRCTL_PWRSEQ
 	tristate
 	select POWER_SEQUENCING
 	select PCI_PWRCTL
+
+config PCI_PWRCTL_SLOT
+	tristate "PCI Power Control driver for PCI slots"
+	select PCI_PWRCTL
+	help
+	  Say Y here to enable the PCI Power Control driver to control the power
+	  state of PCI slots.
+
+	  This is a generic driver that controls the power state of different
+	  PCI slots. The voltage regulators powering the rails of the PCI slots
+	  are expected to be defined in the devicetree node of the PCI bridge.

drivers/pci/pwrctrl/Makefile

@@ -4,3 +4,6 @@ obj-$(CONFIG_PCI_PWRCTL)		+= pci-pwrctrl-core.o
 pci-pwrctrl-core-y			:= core.o
 
 obj-$(CONFIG_PCI_PWRCTL_PWRSEQ)		+= pci-pwrctrl-pwrseq.o
+
+obj-$(CONFIG_PCI_PWRCTL_SLOT)		+= pci-pwrctl-slot.o
+pci-pwrctl-slot-y			:= slot.o

drivers/pci/pwrctrl/slot.c

@@ -0,0 +1,93 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2024 Linaro Ltd.
+ * Author: Manivannan Sadhasivam <[email protected]>
+ */
+
+#include <linux/device.h>
+#include <linux/mod_devicetable.h>
+#include <linux/module.h>
+#include <linux/pci-pwrctrl.h>
+#include <linux/platform_device.h>
+#include <linux/regulator/consumer.h>
+#include <linux/slab.h>
+
+struct pci_pwrctrl_slot_data {
+	struct pci_pwrctrl ctx;
+	struct regulator_bulk_data *supplies;
+	int num_supplies;
+};
+
+static void devm_pci_pwrctrl_slot_power_off(void *data)
+{
+	struct pci_pwrctrl_slot_data *slot = data;
+
+	regulator_bulk_disable(slot->num_supplies, slot->supplies);
+	regulator_bulk_free(slot->num_supplies, slot->supplies);
+}
+
+static int pci_pwrctrl_slot_probe(struct platform_device *pdev)
+{
+	struct pci_pwrctrl_slot_data *slot;
+	struct device *dev = &pdev->dev;
+	int ret;
+
+	slot = devm_kzalloc(dev, sizeof(*slot), GFP_KERNEL);
+	if (!slot)
+		return -ENOMEM;
+
+	ret = of_regulator_bulk_get_all(dev, dev_of_node(dev),
+					&slot->supplies);
+	if (ret < 0) {
+		dev_err_probe(dev, ret, "Failed to get slot regulators\n");
+		return ret;
+	}
+
+	slot->num_supplies = ret;
+	ret = regulator_bulk_enable(slot->num_supplies, slot->supplies);
+	if (ret < 0) {
+		dev_err_probe(dev, ret, "Failed to enable slot regulators\n");
+		goto err_regulator_free;
+	}
+
+	ret = devm_add_action_or_reset(dev, devm_pci_pwrctrl_slot_power_off,
+				       slot);
+	if (ret)
+		goto err_regulator_disable;
+
+	pci_pwrctrl_init(&slot->ctx, dev);
+
+	ret = devm_pci_pwrctrl_device_set_ready(dev, &slot->ctx);
+	if (ret)
+		return dev_err_probe(dev, ret, "Failed to register pwrctrl driver\n");
+
+	return 0;
+
+err_regulator_disable:
+	regulator_bulk_disable(slot->num_supplies, slot->supplies);
+err_regulator_free:
+	regulator_bulk_free(slot->num_supplies, slot->supplies);
+
+	return ret;
+}
+
+static const struct of_device_id pci_pwrctrl_slot_of_match[] = {
+	{
+		.compatible = "pciclass,0604",
+	},
+	{ }
+};
+MODULE_DEVICE_TABLE(of, pci_pwrctrl_slot_of_match);
+
+static struct platform_driver pci_pwrctrl_slot_driver = {
+	.driver = {
+		.name = "pci-pwrctrl-slot",
+		.of_match_table = pci_pwrctrl_slot_of_match,
+	},
+	.probe = pci_pwrctrl_slot_probe,
+};
+module_platform_driver(pci_pwrctrl_slot_driver);
+
+MODULE_AUTHOR("Manivannan Sadhasivam <[email protected]>");
+MODULE_DESCRIPTION("Generic PCI Power Control driver for PCI Slots");
+MODULE_LICENSE("GPL");