net: Add a layer for non-PHY MII time stamping drivers.

While PHY time stamping drivers can simply attach their interface
directly to the PHY instance, stand alone drivers require support in
order to manage their services.  Non-PHY MII time stamping drivers
have a control interface over another bus like I2C, SPI, UART, or via
a memory mapped peripheral.  The controller device will be associated
with one or more time stamping channels, each of which sits snoops in
on a MII bus.

This patch provides a glue layer that will enable time stamping
channels to find their controlling device.
Signed-off-by: Richard Cochran <richardcochran@gmail.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/phy/Makefile

@@ -43,6 +43,8 @@ obj-$(CONFIG_MDIO_SUN4I)	+= mdio-sun4i.o
 obj-$(CONFIG_MDIO_THUNDER)	+= mdio-thunder.o
 obj-$(CONFIG_MDIO_XGENE)	+= mdio-xgene.o
 
+obj-$(CONFIG_NETWORK_PHY_TIMESTAMPING) += mii_timestamper.o
+
 obj-$(CONFIG_SFP)		+= sfp.o
 sfp-obj-$(CONFIG_SFP)		+= sfp-bus.o
 obj-y				+= $(sfp-obj-y) $(sfp-obj-m)

drivers/net/phy/mii_timestamper.c

+// SPDX-License-Identifier: GPL-2.0
+//
+// Support for generic time stamping devices on MII buses.
+// Copyright (C) 2018 Richard Cochran <richardcochran@gmail.com>
+//
+
+#include <linux/mii_timestamper.h>
+
+static LIST_HEAD(mii_timestamping_devices);
+static DEFINE_MUTEX(tstamping_devices_lock);
+
+struct mii_timestamping_desc {
+	struct list_head list;
+	struct mii_timestamping_ctrl *ctrl;
+	struct device *device;
+};
+
+/**
+ * register_mii_tstamp_controller() - registers an MII time stamping device.
+ *
+ * @device:	The device to be registered.
+ * @ctrl:	Pointer to device's control interface.
+ *
+ * Returns zero on success or non-zero on failure.
+ */
+int register_mii_tstamp_controller(struct device *device,
+				   struct mii_timestamping_ctrl *ctrl)
+{
+	struct mii_timestamping_desc *desc;
+
+	desc = kzalloc(sizeof(*desc), GFP_KERNEL);
+	if (!desc)
+		return -ENOMEM;
+
+	INIT_LIST_HEAD(&desc->list);
+	desc->ctrl = ctrl;
+	desc->device = device;
+
+	mutex_lock(&tstamping_devices_lock);
+	list_add_tail(&mii_timestamping_devices, &desc->list);
+	mutex_unlock(&tstamping_devices_lock);
+
+	return 0;
+}
+EXPORT_SYMBOL(register_mii_tstamp_controller);
+
+/**
+ * unregister_mii_tstamp_controller() - unregisters an MII time stamping device.
+ *
+ * @device:	A device previously passed to register_mii_tstamp_controller().
+ */
+void unregister_mii_tstamp_controller(struct device *device)
+{
+	struct mii_timestamping_desc *desc;
+	struct list_head *this, *next;
+
+	mutex_lock(&tstamping_devices_lock);
+	list_for_each_safe(this, next, &mii_timestamping_devices) {
+		desc = list_entry(this, struct mii_timestamping_desc, list);
+		if (desc->device == device) {
+			list_del_init(&desc->list);
+			kfree(desc);
+			break;
+		}
+	}
+	mutex_unlock(&tstamping_devices_lock);
+}
+EXPORT_SYMBOL(unregister_mii_tstamp_controller);
+
+/**
+ * register_mii_timestamper - Enables a given port of an MII time stamper.
+ *
+ * @node:	The device tree node of the MII time stamp controller.
+ * @port:	The index of the port to be enabled.
+ *
+ * Returns a valid interface on success or ERR_PTR otherwise.
+ */
+struct mii_timestamper *register_mii_timestamper(struct device_node *node,
+						 unsigned int port)
+{
+	struct mii_timestamper *mii_ts = NULL;
+	struct mii_timestamping_desc *desc;
+	struct list_head *this;
+
+	mutex_lock(&tstamping_devices_lock);
+	list_for_each(this, &mii_timestamping_devices) {
+		desc = list_entry(this, struct mii_timestamping_desc, list);
+		if (desc->device->of_node == node) {
+			mii_ts = desc->ctrl->probe_channel(desc->device, port);
+			if (!IS_ERR(mii_ts)) {
+				mii_ts->device = desc->device;
+				get_device(desc->device);
+			}
+			break;
+		}
+	}
+	mutex_unlock(&tstamping_devices_lock);
+
+	return mii_ts ? mii_ts : ERR_PTR(-EPROBE_DEFER);
+}
+EXPORT_SYMBOL(register_mii_timestamper);
+
+/**
+ * unregister_mii_timestamper - Disables a given MII time stamper.
+ *
+ * @mii_ts:	An interface obtained via register_mii_timestamper().
+ *
+ */
+void unregister_mii_timestamper(struct mii_timestamper *mii_ts)
+{
+	struct mii_timestamping_desc *desc;
+	struct list_head *this;
+
+	mutex_lock(&tstamping_devices_lock);
+	list_for_each(this, &mii_timestamping_devices) {
+		desc = list_entry(this, struct mii_timestamping_desc, list);
+		if (desc->device == mii_ts->device) {
+			desc->ctrl->release_channel(desc->device, mii_ts);
+			put_device(desc->device);
+			break;
+		}
+	}
+	mutex_unlock(&tstamping_devices_lock);
+}
+EXPORT_SYMBOL(unregister_mii_timestamper);

include/linux/mii_timestamper.h

@@ -33,10 +33,15 @@ struct phy_device;
  *		the phy_device mutex.
  *
  * @ts_info:	Handles ethtool queries for hardware time stamping.
+ * @device:	Remembers the device to which the instance belongs.
  *
  * Drivers for PHY time stamping devices should embed their
  * mii_timestamper within a private structure, obtaining a reference
  * to it using container_of().
+ *
+ * Drivers for non-PHY time stamping devices should return a pointer
+ * to a mii_timestamper from the probe_channel() callback of their
+ * mii_timestamping_ctrl interface.
  */
 struct mii_timestamper {
 	bool (*rxtstamp)(struct mii_timestamper *mii_ts,
@@ -53,6 +58,64 @@ struct mii_timestamper {
 
 	int  (*ts_info)(struct mii_timestamper *mii_ts,
 			struct ethtool_ts_info *ts_info);
+
+	struct device *device;
+};
+
+/**
+ * struct mii_timestamping_ctrl - MII time stamping controller interface.
+ *
+ * @probe_channel:	Callback into the controller driver announcing the
+ *			presence of the 'port' channel.  The 'device' field
+ *			had been passed to register_mii_tstamp_controller().
+ *			The driver must return either a pointer to a valid
+ *			MII timestamper instance or PTR_ERR.
+ *
+ * @release_channel:	Releases an instance obtained via .probe_channel.
+ */
+struct mii_timestamping_ctrl {
+	struct mii_timestamper *(*probe_channel)(struct device *device,
+						 unsigned int port);
+	void (*release_channel)(struct device *device,
+				struct mii_timestamper *mii_ts);
 };
 
+#ifdef CONFIG_NETWORK_PHY_TIMESTAMPING
+
+int register_mii_tstamp_controller(struct device *device,
+				   struct mii_timestamping_ctrl *ctrl);
+
+void unregister_mii_tstamp_controller(struct device *device);
+
+struct mii_timestamper *register_mii_timestamper(struct device_node *node,
+						 unsigned int port);
+
+void unregister_mii_timestamper(struct mii_timestamper *mii_ts);
+
+#else
+
+static inline
+int register_mii_tstamp_controller(struct device *device,
+				   struct mii_timestamping_ctrl *ctrl)
+{
+	return -EOPNOTSUPP;
+}
+
+static inline void unregister_mii_tstamp_controller(struct device *device)
+{
+}
+
+static inline
+struct mii_timestamper *register_mii_timestamper(struct device_node *node,
+						 unsigned int port)
+{
+	return NULL;
+}
+
+static inline void unregister_mii_timestamper(struct mii_timestamper *mii_ts)
+{
+}
+
+#endif
+
 #endif

net/Kconfig

@@ -108,9 +108,10 @@ config NETWORK_PHY_TIMESTAMPING
 	bool "Timestamping in PHY devices"
 	select NET_PTP_CLASSIFY
 	help
-	  This allows timestamping of network packets by PHYs with
-	  hardware timestamping capabilities. This option adds some
-	  overhead in the transmit and receive paths.
+	  This allows timestamping of network packets by PHYs (or
+	  other MII bus snooping devices) with hardware timestamping
+	  capabilities. This option adds some overhead in the transmit
+	  and receive paths.
 
 	  If you are unsure how to answer this question, answer N.