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>

2 files changed, 127 insertions, 0 deletions

diff --git a/drivers/net/phy/Makefile b/drivers/net/phy/Makefile
index d846b4dc1c68..fe5badf13b65 100644
--- a/drivers/net/phy/Makefile
+++ b/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)
diff --git a/drivers/net/phy/mii_timestamper.c b/drivers/net/phy/mii_timestamper.c
new file mode 100644
index 000000000000..2f12c5d901df
--- /dev/null
+++ b/drivers/net/phy/mii_timestamper.c
@@ -0,0 +1,125 @@
+// 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);