net: add framework to support Ethernet PSE and PDs devices

This framework was create with intention to provide support for Ethernet PSE
(Power Sourcing Equipment) and PDs (Powered Device).

At current step this patch implements generic PSE support for PoDL (Power over
Data Lines 802.3bu) specification with reserving name space for PD devices as
well.

This framework can be extended to support 802.3af and 802.3at "Power via the
Media Dependent Interface" (or PoE/Power over Ethernet)

Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/Kconfig

@@ -500,6 +500,8 @@ config NET_SB1000
 
 source "drivers/net/phy/Kconfig"
 
+source "drivers/net/pse-pd/Kconfig"
+
 source "drivers/net/can/Kconfig"
 
 source "drivers/net/mctp/Kconfig"

drivers/net/Makefile

@@ -23,6 +23,7 @@ obj-$(CONFIG_NET) += loopback.o
 obj-$(CONFIG_NETDEV_LEGACY_INIT) += Space.o
 obj-$(CONFIG_NETCONSOLE) += netconsole.o
 obj-y += phy/
+obj-y += pse-pd/
 obj-y += mdio/
 obj-y += pcs/
 obj-$(CONFIG_RIONET) += rionet.o

drivers/net/pse-pd/Kconfig

@@ -0,0 +1,11 @@
+# SPDX-License-Identifier: GPL-2.0-only
+#
+# Ethernet Power Sourcing Equipment drivers
+#
+
+menuconfig PSE_CONTROLLER
+	bool "Ethernet Power Sourcing Equipment Support"
+	help
+	  Generic Power Sourcing Equipment Controller support.
+
+	  If unsure, say no.

drivers/net/pse-pd/Makefile

@@ -0,0 +1,4 @@
+# SPDX-License-Identifier: GPL-2.0-only
+# Makefile for Linux PSE drivers
+
+obj-$(CONFIG_PSE_CONTROLLER) += pse_core.o

drivers/net/pse-pd/pse_core.c

@@ -0,0 +1,256 @@
+// SPDX-License-Identifier: GPL-2.0-only
+//
+// Framework for Ethernet Power Sourcing Equipment
+//
+// Copyright (c) 2022 Pengutronix, Oleksij Rempel <kernel@pengutronix.de>
+//
+
+#include <linux/device.h>
+#include <linux/of.h>
+#include <linux/pse-pd/pse.h>
+
+static DEFINE_MUTEX(pse_list_mutex);
+static LIST_HEAD(pse_controller_list);
+
+/**
+ * struct pse_control - a PSE control
+ * @pcdev: a pointer to the PSE controller device
+ *         this PSE control belongs to
+ * @list: list entry for the pcdev's PSE controller list
+ * @id: ID of the PSE line in the PSE controller device
+ * @refcnt: Number of gets of this pse_control
+ */
+struct pse_control {
+	struct pse_controller_dev *pcdev;
+	struct list_head list;
+	unsigned int id;
+	struct kref refcnt;
+};
+
+/**
+ * of_pse_zero_xlate - dummy function for controllers with one only control
+ * @pcdev: a pointer to the PSE controller device
+ * @pse_spec: PSE line specifier as found in the device tree
+ *
+ * This static translation function is used by default if of_xlate in
+ * :c:type:`pse_controller_dev` is not set. It is useful for all PSE
+ * controllers with #pse-cells = <0>.
+ */
+static int of_pse_zero_xlate(struct pse_controller_dev *pcdev,
+			     const struct of_phandle_args *pse_spec)
+{
+	return 0;
+}
+
+/**
+ * of_pse_simple_xlate - translate pse_spec to the PSE line number
+ * @pcdev: a pointer to the PSE controller device
+ * @pse_spec: PSE line specifier as found in the device tree
+ *
+ * This static translation function is used by default if of_xlate in
+ * :c:type:`pse_controller_dev` is not set. It is useful for all PSE
+ * controllers with 1:1 mapping, where PSE lines can be indexed by number
+ * without gaps.
+ */
+static int of_pse_simple_xlate(struct pse_controller_dev *pcdev,
+			       const struct of_phandle_args *pse_spec)
+{
+	if (pse_spec->args[0] >= pcdev->nr_lines)
+		return -EINVAL;
+
+	return pse_spec->args[0];
+}
+
+/**
+ * pse_controller_register - register a PSE controller device
+ * @pcdev: a pointer to the initialized PSE controller device
+ */
+int pse_controller_register(struct pse_controller_dev *pcdev)
+{
+	if (!pcdev->of_xlate) {
+		if (pcdev->of_pse_n_cells == 0)
+			pcdev->of_xlate = of_pse_zero_xlate;
+		else if (pcdev->of_pse_n_cells == 1)
+			pcdev->of_xlate = of_pse_simple_xlate;
+	}
+
+	mutex_init(&pcdev->lock);
+	INIT_LIST_HEAD(&pcdev->pse_control_head);
+
+	mutex_lock(&pse_list_mutex);
+	list_add(&pcdev->list, &pse_controller_list);
+	mutex_unlock(&pse_list_mutex);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(pse_controller_register);
+
+/**
+ * pse_controller_unregister - unregister a PSE controller device
+ * @pcdev: a pointer to the PSE controller device
+ */
+void pse_controller_unregister(struct pse_controller_dev *pcdev)
+{
+	mutex_lock(&pse_list_mutex);
+	list_del(&pcdev->list);
+	mutex_unlock(&pse_list_mutex);
+}
+EXPORT_SYMBOL_GPL(pse_controller_unregister);
+
+static void devm_pse_controller_release(struct device *dev, void *res)
+{
+	pse_controller_unregister(*(struct pse_controller_dev **)res);
+}
+
+/**
+ * devm_pse_controller_register - resource managed pse_controller_register()
+ * @dev: device that is registering this PSE controller
+ * @pcdev: a pointer to the initialized PSE controller device
+ *
+ * Managed pse_controller_register(). For PSE controllers registered by
+ * this function, pse_controller_unregister() is automatically called on
+ * driver detach. See pse_controller_register() for more information.
+ */
+int devm_pse_controller_register(struct device *dev,
+				 struct pse_controller_dev *pcdev)
+{
+	struct pse_controller_dev **pcdevp;
+	int ret;
+
+	pcdevp = devres_alloc(devm_pse_controller_release, sizeof(*pcdevp),
+			      GFP_KERNEL);
+	if (!pcdevp)
+		return -ENOMEM;
+
+	ret = pse_controller_register(pcdev);
+	if (ret) {
+		devres_free(pcdevp);
+		return ret;
+	}
+
+	*pcdevp = pcdev;
+	devres_add(dev, pcdevp);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(devm_pse_controller_register);
+
+/* PSE control section */
+
+static void __pse_control_release(struct kref *kref)
+{
+	struct pse_control *psec = container_of(kref, struct pse_control,
+						  refcnt);
+
+	lockdep_assert_held(&pse_list_mutex);
+
+	module_put(psec->pcdev->owner);
+
+	list_del(&psec->list);
+	kfree(psec);
+}
+
+static void __pse_control_put_internal(struct pse_control *psec)
+{
+	lockdep_assert_held(&pse_list_mutex);
+
+	kref_put(&psec->refcnt, __pse_control_release);
+}
+
+/**
+ * pse_control_put - free the PSE control
+ * @psec: PSE control pointer
+ */
+void pse_control_put(struct pse_control *psec)
+{
+	if (IS_ERR_OR_NULL(psec))
+		return;
+
+	mutex_lock(&pse_list_mutex);
+	__pse_control_put_internal(psec);
+	mutex_unlock(&pse_list_mutex);
+}
+EXPORT_SYMBOL_GPL(pse_control_put);
+
+static struct pse_control *
+pse_control_get_internal(struct pse_controller_dev *pcdev, unsigned int index)
+{
+	struct pse_control *psec;
+
+	lockdep_assert_held(&pse_list_mutex);
+
+	list_for_each_entry(psec, &pcdev->pse_control_head, list) {
+		if (psec->id == index) {
+			kref_get(&psec->refcnt);
+			return psec;
+		}
+	}
+
+	psec = kzalloc(sizeof(*psec), GFP_KERNEL);
+	if (!psec)
+		return ERR_PTR(-ENOMEM);
+
+	if (!try_module_get(pcdev->owner)) {
+		kfree(psec);
+		return ERR_PTR(-ENODEV);
+	}
+
+	psec->pcdev = pcdev;
+	list_add(&psec->list, &pcdev->pse_control_head);
+	psec->id = index;
+	kref_init(&psec->refcnt);
+
+	return psec;
+}
+
+struct pse_control *
+of_pse_control_get(struct device_node *node)
+{
+	struct pse_controller_dev *r, *pcdev;
+	struct of_phandle_args args;
+	struct pse_control *psec;
+	int psec_id;
+	int ret;
+
+	if (!node)
+		return ERR_PTR(-EINVAL);
+
+	ret = of_parse_phandle_with_args(node, "pses", "#pse-cells", 0, &args);
+	if (ret)
+		return ERR_PTR(ret);
+
+	mutex_lock(&pse_list_mutex);
+	pcdev = NULL;
+	list_for_each_entry(r, &pse_controller_list, list) {
+		if (args.np == r->dev->of_node) {
+			pcdev = r;
+			break;
+		}
+	}
+
+	if (!pcdev) {
+		psec = ERR_PTR(-EPROBE_DEFER);
+		goto out;
+	}
+
+	if (WARN_ON(args.args_count != pcdev->of_pse_n_cells)) {
+		psec = ERR_PTR(-EINVAL);
+		goto out;
+	}
+
+	psec_id = pcdev->of_xlate(pcdev, &args);
+	if (psec_id < 0) {
+		psec = ERR_PTR(psec_id);
+		goto out;
+	}
+
+	/* pse_list_mutex also protects the pcdev's pse_control list */
+	psec = pse_control_get_internal(pcdev, psec_id);
+
+out:
+	mutex_unlock(&pse_list_mutex);
+	of_node_put(args.np);
+
+	return psec;
+}
+EXPORT_SYMBOL_GPL(of_pse_control_get);

include/linux/pse-pd/pse.h

@@ -0,0 +1,67 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+// Copyright (c) 2022 Pengutronix, Oleksij Rempel <kernel@pengutronix.de>
+ */
+#ifndef _LINUX_PSE_CONTROLLER_H
+#define _LINUX_PSE_CONTROLLER_H
+
+#include <linux/ethtool.h>
+#include <linux/list.h>
+#include <uapi/linux/ethtool.h>
+
+struct module;
+struct device_node;
+struct of_phandle_args;
+struct pse_control;
+
+/**
+ * struct pse_controller_dev - PSE controller entity that might
+ *                             provide multiple PSE controls
+ * @ops: a pointer to device specific struct pse_controller_ops
+ * @owner: kernel module of the PSE controller driver
+ * @list: internal list of PSE controller devices
+ * @pse_control_head: head of internal list of requested PSE controls
+ * @dev: corresponding driver model device struct
+ * @of_pse_n_cells: number of cells in PSE line specifiers
+ * @of_xlate: translation function to translate from specifier as found in the
+ *            device tree to id as given to the PSE control ops
+ * @nr_lines: number of PSE controls in this controller device
+ * @lock: Mutex for serialization access to the PSE controller
+ */
+struct pse_controller_dev {
+	const struct pse_controller_ops *ops;
+	struct module *owner;
+	struct list_head list;
+	struct list_head pse_control_head;
+	struct device *dev;
+	int of_pse_n_cells;
+	int (*of_xlate)(struct pse_controller_dev *pcdev,
+			const struct of_phandle_args *pse_spec);
+	unsigned int nr_lines;
+	struct mutex lock;
+};
+
+#if IS_ENABLED(CONFIG_PSE_CONTROLLER)
+int pse_controller_register(struct pse_controller_dev *pcdev);
+void pse_controller_unregister(struct pse_controller_dev *pcdev);
+struct device;
+int devm_pse_controller_register(struct device *dev,
+				 struct pse_controller_dev *pcdev);
+
+struct pse_control *of_pse_control_get(struct device_node *node);
+void pse_control_put(struct pse_control *psec);
+
+#else
+
+static inline struct pse_control *of_pse_control_get(struct device_node *node)
+{
+	return ERR_PTR(-ENOENT);
+}
+
+static inline void pse_control_put(struct pse_control *psec)
+{
+}
+
+#endif
+
+#endif