[PATCH v17 4/6] fpga: add fpga bridge framework

[Alan Tull]

This framework adds API functions for enabling/
disabling FPGA bridges under kernel control.

This allows the Linux kernel to disable FPGA bridges
during FPGA reprogramming and to enable FPGA bridges
when FPGA reprogramming is done.  This framework is
be manufacturer-agnostic, allowing it to be used in
interfaces that use the FPGA Manager Framework to
reprogram FPGA's.

The functions are:
* of_fpga_bridge_get
* fpga_bridge_put
   Get/put an exclusive reference to a FPGA bridge.

* fpga_bridge_enable
* fpga_bridge_disable
   Enable/Disable traffic through a bridge.

* fpga_bridge_register
* fpga_bridge_unregister
   Register/unregister a device-specific low level FPGA
   Bridge driver.

Get an exclusive reference to a bridge and add it to a list:
* fpga_bridge_get_to_list

To enable/disable/put a set of bridges that are on a list:
* fpga_bridges_enable
* fpga_bridges_disable
* fpga_bridges_put

Signed-off-by: Alan Tull <atull@xxxxxxxxxxxxxxxxxxxxx>
---
v2:  Minor cleanup
v12: Bump version to line up with simple fpga bus
     Remove sysfs
     Improve get/put functions, get the low level driver too.
     Clean up class implementation
     Add kernel doc documentation
     Rename (un)register_fpga_bridge -> fpga_bridge_(un)register
v13: Add inlined empty functions for if not CONFIG_FPGA_BRIDGE
     Clean up debugging
     Remove unneeded #include in .h
     Remove unnecessary prints
     Remove 'label' DT binding.
     Document the mutex
v14: Allow bridges with no ops
     *const* struct fpga_bridge_ops
     Add functions to git/put/enable/disable list of bridges
     Add list node to struct fpga_bridge
     Do of_node_get/put in of_fpga_bridge_get()
     Add r/o attributes: name and state
v15: No change in this patch for v15 of this patch set
v16: Remove of_get_fpga_bus function
v17: No change to this patch in v17 of patch set
---
 drivers/fpga/Kconfig             |    7 +
 drivers/fpga/Makefile            |    3 +
 drivers/fpga/fpga-bridge.c       |  388 ++++++++++++++++++++++++++++++++++++++
 include/linux/fpga/fpga-bridge.h |   55 ++++++
 4 files changed, 453 insertions(+)
 create mode 100644 drivers/fpga/fpga-bridge.c
 create mode 100644 include/linux/fpga/fpga-bridge.h

diff --git a/drivers/fpga/Kconfig b/drivers/fpga/Kconfig
index c9b9fdf..b6cfd89 100644
--- a/drivers/fpga/Kconfig
+++ b/drivers/fpga/Kconfig
@@ -24,6 +24,13 @@ config FPGA_MGR_ZYNQ_FPGA
 	help
 	  FPGA manager driver support for Xilinx Zynq FPGAs.
 
+config FPGA_BRIDGE
+       bool "FPGA Bridge Framework"
+       depends on OF
+       help
+         Say Y here if you want to support bridges connected between host
+	 processors and FPGAs or between FPGAs.
+
 endif # FPGA
 
 endmenu
diff --git a/drivers/fpga/Makefile b/drivers/fpga/Makefile
index 8d83fc6..4baef00 100644
--- a/drivers/fpga/Makefile
+++ b/drivers/fpga/Makefile
@@ -8,3 +8,6 @@ obj-$(CONFIG_FPGA)			+= fpga-mgr.o
 # FPGA Manager Drivers
 obj-$(CONFIG_FPGA_MGR_SOCFPGA)		+= socfpga.o
 obj-$(CONFIG_FPGA_MGR_ZYNQ_FPGA)	+= zynq-fpga.o
+
+# FPGA Bridge Drivers
+obj-$(CONFIG_FPGA_BRIDGE)		+= fpga-bridge.o
diff --git a/drivers/fpga/fpga-bridge.c b/drivers/fpga/fpga-bridge.c
new file mode 100644
index 0000000..5119d8e
--- /dev/null
+++ b/drivers/fpga/fpga-bridge.c
@@ -0,0 +1,388 @@
+/*
+ * FPGA Bridge Framework Driver
+ *
+ *  Copyright (C) 2013-2015 Altera Corporation, All Rights Reserved.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+#include <linux/fpga/fpga-bridge.h>
+#include <linux/idr.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/of_platform.h>
+#include <linux/slab.h>
+#include <linux/spinlock.h>
+
+static DEFINE_IDA(fpga_bridge_ida);
+static struct class *fpga_bridge_class;
+
+/* Lock for adding/removing bridges to linked lists*/
+spinlock_t bridge_list_lock;
+
+static int fpga_bridge_of_node_match(struct device *dev, const void *data)
+{
+	return dev->of_node == data;
+}
+
+/**
+ * fpga_bridge_enable - Enable transactions on the bridge
+ *
+ * @bridge: FPGA bridge
+ *
+ * Return: 0 for success, error code otherwise.
+ */
+int fpga_bridge_enable(struct fpga_bridge *bridge)
+{
+	dev_dbg(&bridge->dev, "enable\n");
+
+	if (bridge->br_ops && bridge->br_ops->enable_set)
+		return bridge->br_ops->enable_set(bridge, 1);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(fpga_bridge_enable);
+
+/**
+ * fpga_bridge_disable - Disable transactions on the bridge
+ *
+ * @bridge: FPGA bridge
+ *
+ * Return: 0 for success, error code otherwise.
+ */
+int fpga_bridge_disable(struct fpga_bridge *bridge)
+{
+	dev_dbg(&bridge->dev, "disable\n");
+
+	if (bridge->br_ops && bridge->br_ops->enable_set)
+		return bridge->br_ops->enable_set(bridge, 0);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(fpga_bridge_disable);
+
+/**
+ * of_fpga_bridge_get - get an exclusive reference to a fpga bridge
+ *
+ * @np: node pointer of a FPGA bridge
+ *
+ * Return fpga_bridge struct if successful.
+ * Return -EBUSY if someone already has a reference to the bridge.
+ * Return -ENODEV if @np is not a FPGA Bridge.
+ */
+struct fpga_bridge *of_fpga_bridge_get(struct device_node *np)
+{
+	struct device *dev;
+	struct fpga_bridge *bridge;
+	int ret = -ENODEV;
+
+	of_node_get(np);
+
+	dev = class_find_device(fpga_bridge_class, NULL, np,
+				fpga_bridge_of_node_match);
+	if (!dev)
+		goto err_dev;
+
+	bridge = to_fpga_bridge(dev);
+	if (!bridge)
+		goto err_dev;
+
+	if (!mutex_trylock(&bridge->mutex)) {
+		ret = -EBUSY;
+		goto err_dev;
+	}
+
+	if (!try_module_get(dev->parent->driver->owner))
+		goto err_ll_mod;
+
+	dev_dbg(&bridge->dev, "get\n");
+
+	return bridge;
+
+err_ll_mod:
+	mutex_unlock(&bridge->mutex);
+err_dev:
+	put_device(dev);
+	of_node_put(np);
+	return ERR_PTR(ret);
+}
+EXPORT_SYMBOL_GPL(of_fpga_bridge_get);
+
+/**
+ * fpga_bridge_put - release a reference to a bridge
+ *
+ * @bridge: FPGA bridge
+ */
+void fpga_bridge_put(struct fpga_bridge *bridge)
+{
+	dev_dbg(&bridge->dev, "put\n");
+
+	module_put(bridge->dev.parent->driver->owner);
+	mutex_unlock(&bridge->mutex);
+	put_device(&bridge->dev);
+}
+EXPORT_SYMBOL_GPL(fpga_bridge_put);
+
+/**
+ * fpga_bridges_enable - enable bridges in a list
+ * @bridge_list: list of FPGA bridges
+ *
+ * Enable each bridge in the list.  If list is empty, do nothing.
+ *
+ * Return 0 for success or empty bridge list; return error code otherwise.
+ */
+int fpga_bridges_enable(struct list_head *bridge_list)
+{
+	struct fpga_bridge *bridge;
+	struct list_head *node;
+	int ret;
+
+	list_for_each(node, bridge_list) {
+		bridge = list_entry(node, struct fpga_bridge, node);
+		ret = fpga_bridge_enable(bridge);
+		if (ret)
+			return ret;
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(fpga_bridges_enable);
+
+/**
+ * fpga_bridges_disable - disable bridges in a list
+ *
+ * @bridge_list: list of FPGA bridges
+ *
+ * Disable each bridge in the list.  If list is empty, do nothing.
+ *
+ * Return 0 for success or empty bridge list; return error code otherwise.
+ */
+int fpga_bridges_disable(struct list_head *bridge_list)
+{
+	struct fpga_bridge *bridge;
+	struct list_head *node;
+	int ret;
+
+	list_for_each(node, bridge_list) {
+		bridge = list_entry(node, struct fpga_bridge, node);
+		ret = fpga_bridge_disable(bridge);
+		if (ret)
+			return ret;
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(fpga_bridges_disable);
+
+/**
+ * fpga_bridges_put - put bridges
+ *
+ * @bridge_list: list of FPGA bridges
+ *
+ * For each bridge in the list, put the bridge and remove it from the list.
+ * If list is empty, do nothing.
+ */
+void fpga_bridges_put(struct list_head *bridge_list)
+{
+	struct fpga_bridge *bridge;
+	struct list_head *node, *next;
+	unsigned long flags;
+
+	list_for_each_safe(node, next, bridge_list) {
+		bridge = list_entry(node, struct fpga_bridge, node);
+
+		fpga_bridge_put(bridge);
+
+		spin_lock_irqsave(&bridge_list_lock, flags);
+		list_del(&bridge->node);
+		spin_unlock_irqrestore(&bridge_list_lock, flags);
+	}
+}
+EXPORT_SYMBOL_GPL(fpga_bridges_put);
+
+/**
+ * fpga_bridges_get_to_list - get a bridge, add it to a list
+ *
+ * @np: node pointer of a FPGA bridge
+ * @bridge_list: list of FPGA bridges
+ *
+ * Get an exclusive reference to the bridge and and it to the list.
+ *
+ * Return 0 for success, error code from of_fpga_bridge_get() othewise.
+ */
+int fpga_bridge_get_to_list(struct device_node *np,
+			    struct list_head *bridge_list)
+{
+	struct fpga_bridge *bridge;
+	unsigned long flags;
+
+	bridge = of_fpga_bridge_get(np);
+	if (IS_ERR(bridge))
+		return PTR_ERR(bridge);
+
+	spin_lock_irqsave(&bridge_list_lock, flags);
+	list_add(&bridge->node, bridge_list);
+	spin_unlock_irqrestore(&bridge_list_lock, flags);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(fpga_bridge_get_to_list);
+
+static ssize_t name_show(struct device *dev,
+			 struct device_attribute *attr, char *buf)
+{
+	struct fpga_bridge *bridge = to_fpga_bridge(dev);
+
+	return sprintf(buf, "%s\n", bridge->name);
+}
+
+static ssize_t state_show(struct device *dev,
+			  struct device_attribute *attr, char *buf)
+{
+	struct fpga_bridge *bridge = to_fpga_bridge(dev);
+	int enable = 1;
+
+	if (bridge->br_ops && bridge->br_ops->enable_show)
+		enable = bridge->br_ops->enable_show(bridge);
+
+	return sprintf(buf, "%s\n", enable ? "enabled" : "disabled");
+}
+
+static DEVICE_ATTR_RO(name);
+static DEVICE_ATTR_RO(state);
+
+static struct attribute *fpga_bridge_attrs[] = {
+	&dev_attr_name.attr,
+	&dev_attr_state.attr,
+	NULL,
+};
+ATTRIBUTE_GROUPS(fpga_bridge);
+
+/**
+ * fpga_bridge_register - register a fpga bridge driver
+ * @dev:	FPGA bridge device from pdev
+ * @name:	FPGA bridge name
+ * @br_ops:	pointer to structure of fpga bridge ops
+ * @priv:	FPGA bridge private data
+ *
+ * Return: 0 for success, error code otherwise.
+ */
+int fpga_bridge_register(struct device *dev, const char *name,
+			 const struct fpga_bridge_ops *br_ops, void *priv)
+{
+	struct fpga_bridge *bridge;
+	int id, ret = 0;
+
+	if (!name || !strlen(name)) {
+		dev_err(dev, "Attempt to register with no name!\n");
+		return -EINVAL;
+	}
+
+	bridge = kzalloc(sizeof(*bridge), GFP_KERNEL);
+	if (!bridge)
+		return -ENOMEM;
+
+	id = ida_simple_get(&fpga_bridge_ida, 0, 0, GFP_KERNEL);
+	if (id < 0) {
+		ret = id;
+		goto error_kfree;
+	}
+
+	mutex_init(&bridge->mutex);
+	INIT_LIST_HEAD(&bridge->node);
+
+	bridge->name = name;
+	bridge->br_ops = br_ops;
+	bridge->priv = priv;
+
+	device_initialize(&bridge->dev);
+	bridge->dev.class = fpga_bridge_class;
+	bridge->dev.parent = dev;
+	bridge->dev.of_node = dev->of_node;
+	bridge->dev.id = id;
+	dev_set_drvdata(dev, bridge);
+
+	ret = dev_set_name(&bridge->dev, "br%d", id);
+	if (ret)
+		goto error_device;
+
+	ret = device_add(&bridge->dev);
+	if (ret)
+		goto error_device;
+
+	dev_info(bridge->dev.parent, "fpga bridge [%s] registered\n",
+		 bridge->name);
+
+	return 0;
+
+error_device:
+	ida_simple_remove(&fpga_bridge_ida, id);
+error_kfree:
+	kfree(bridge);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(fpga_bridge_register);
+
+/**
+ * fpga_bridge_unregister - unregister a fpga bridge driver
+ * @dev: FPGA bridge device from pdev
+ */
+void fpga_bridge_unregister(struct device *dev)
+{
+	struct fpga_bridge *bridge = dev_get_drvdata(dev);
+
+	/*
+	 * If the low level driver provides a method for putting bridge into
+	 * a desired state upon unregister, do it.
+	 */
+	if (bridge->br_ops && bridge->br_ops->fpga_bridge_remove)
+		bridge->br_ops->fpga_bridge_remove(bridge);
+
+	device_unregister(&bridge->dev);
+}
+EXPORT_SYMBOL_GPL(fpga_bridge_unregister);
+
+static void fpga_bridge_dev_release(struct device *dev)
+{
+	struct fpga_bridge *bridge = to_fpga_bridge(dev);
+
+	ida_simple_remove(&fpga_bridge_ida, bridge->dev.id);
+	kfree(bridge);
+}
+
+static int __init fpga_bridge_dev_init(void)
+{
+	spin_lock_init(&bridge_list_lock);
+
+	fpga_bridge_class = class_create(THIS_MODULE, "fpga_bridge");
+	if (IS_ERR(fpga_bridge_class))
+		return PTR_ERR(fpga_bridge_class);
+
+	fpga_bridge_class->dev_groups = fpga_bridge_groups;
+	fpga_bridge_class->dev_release = fpga_bridge_dev_release;
+
+	return 0;
+}
+
+static void __exit fpga_bridge_dev_exit(void)
+{
+	class_destroy(fpga_bridge_class);
+	ida_destroy(&fpga_bridge_ida);
+}
+
+MODULE_DESCRIPTION("FPGA Bridge Driver");
+MODULE_AUTHOR("Alan Tull <atull@xxxxxxxxxxxxxxxxxxxxx>");
+MODULE_LICENSE("GPL v2");
+
+subsys_initcall(fpga_bridge_dev_init);
+module_exit(fpga_bridge_dev_exit);
diff --git a/include/linux/fpga/fpga-bridge.h b/include/linux/fpga/fpga-bridge.h
new file mode 100644
index 0000000..1a96934
--- /dev/null
+++ b/include/linux/fpga/fpga-bridge.h
@@ -0,0 +1,55 @@
+#include <linux/device.h>
+
+#ifndef _LINUX_FPGA_BRIDGE_H
+#define _LINUX_FPGA_BRIDGE_H
+
+struct fpga_bridge;
+
+/**
+ * struct fpga_bridge_ops - ops for low level FPGA bridge drivers
+ * @enable_show: returns the FPGA bridge's status
+ * @enable_set: set a FPGA bridge as enabled or disabled
+ * @fpga_bridge_remove: set FPGA into a specific state during driver remove
+ */
+struct fpga_bridge_ops {
+	int (*enable_show)(struct fpga_bridge *bridge);
+	int (*enable_set)(struct fpga_bridge *bridge, bool enable);
+	void (*fpga_bridge_remove)(struct fpga_bridge *bridge);
+};
+
+/**
+ * struct fpga_bridge - FPGA bridge structure
+ * @name: name of low level FPGA bridge
+ * @dev: FPGA bridge device
+ * @mutex: enforces exclusive reference to bridge
+ * @br_ops: pointer to struct of FPGA bridge ops
+ * @node: FPGA bridge list node
+ * @priv: low level driver private date
+ */
+struct fpga_bridge {
+	const char *name;
+	struct device dev;
+	struct mutex mutex; /* for exclusive reference to bridge */
+	const struct fpga_bridge_ops *br_ops;
+	struct list_head node;
+	void *priv;
+};
+
+#define to_fpga_bridge(d) container_of(d, struct fpga_bridge, dev)
+
+struct fpga_bridge *of_fpga_bridge_get(struct device_node *node);
+void fpga_bridge_put(struct fpga_bridge *bridge);
+int fpga_bridge_enable(struct fpga_bridge *bridge);
+int fpga_bridge_disable(struct fpga_bridge *bridge);
+
+int fpga_bridges_enable(struct list_head *bridge_list);
+int fpga_bridges_disable(struct list_head *bridge_list);
+void fpga_bridges_put(struct list_head *bridge_list);
+int fpga_bridge_get_to_list(struct device_node *np,
+			    struct list_head *bridge_list);
+
+int fpga_bridge_register(struct device *dev, const char *name,
+			 const struct fpga_bridge_ops *br_ops, void *priv);
+void fpga_bridge_unregister(struct device *dev);
+
+#endif /* _LINUX_FPGA_BRIDGE_H */
-- 
1.7.9.5