NTB: Add ping pong test client

This is a simple ping pong driver that exercises the scratch pads and
doorbells of the ntb hardware.  This driver may be used to test that
your ntb hardware and drivers are functioning at a basic level.
Signed-off-by: Allen Hubbe <Allen.Hubbe@emc.com>
Signed-off-by: Jon Mason <jdmason@kudzu.us>

Documentation/ntb.txt

@@ -37,6 +37,33 @@ Transport queue pair.  Network data is copied between socket buffers and the
 Transport queue pair buffer.  The Transport client may be used for other things
 besides Netdev, however no other applications have yet been written.
 
+### NTB Ping Pong Test Client (ntb\_pingpong)
+
+The Ping Pong test client serves as a demonstration to exercise the doorbell
+and scratchpad registers of NTB hardware, and as an example simple NTB client.
+Ping Pong enables the link when started, waits for the NTB link to come up, and
+then proceeds to read and write the doorbell scratchpad registers of the NTB.
+The peers interrupt each other using a bit mask of doorbell bits, which is
+shifted by one in each round, to test the behavior of multiple doorbell bits
+and interrupt vectors.  The Ping Pong driver also reads the first local
+scratchpad, and writes the value plus one to the first peer scratchpad, each
+round before writing the peer doorbell register.
+
+Module Parameters:
+
+* unsafe - Some hardware has known issues with scratchpad and doorbell
+	registers.  By default, Ping Pong will not attempt to exercise such
+	hardware.  You may override this behavior at your own risk by setting
+	unsafe=1.
+* delay\_ms - Specify the delay between receiving a doorbell
+	interrupt event and setting the peer doorbell register for the next
+	round.
+* init\_db - Specify the doorbell bits to start new series of rounds.  A new
+	series begins once all the doorbell bits have been shifted out of
+	range.
+* dyndbg - It is suggested to specify dyndbg=+p when loading this module, and
+	then to observe debugging output on the console.
+
 ## NTB Hardware Drivers
 
 NTB hardware drivers should register devices with the NTB core driver.  After

drivers/ntb/Kconfig

@@ -14,6 +14,8 @@ if NTB
 
 source "drivers/ntb/hw/Kconfig"
 
+source "drivers/ntb/test/Kconfig"
+
 config NTB_TRANSPORT
 	tristate "NTB Transport Client"
 	help

drivers/ntb/Makefile

-obj-$(CONFIG_NTB) += ntb.o hw/
+obj-$(CONFIG_NTB) += ntb.o hw/ test/
 obj-$(CONFIG_NTB_TRANSPORT) += ntb_transport.o

drivers/ntb/test/Kconfig

+config NTB_PINGPONG
+	tristate "NTB Ping Pong Test Client"
+	help
+	 This is a simple ping pong driver that exercises the scratchpads and
+	 doorbells of the ntb hardware.  This driver may be used to test that
+	 your ntb hardware and drivers are functioning at a basic level.
+
+	 If unsure, say N.

drivers/ntb/test/Makefile

+obj-$(CONFIG_NTB_PINGPONG) += ntb_pingpong.o

drivers/ntb/test/ntb_pingpong.c

+/*
+ * This file is provided under a dual BSD/GPLv2 license.  When using or
+ *   redistributing this file, you may do so under either license.
+ *
+ *   GPL LICENSE SUMMARY
+ *
+ *   Copyright (C) 2015 EMC Corporation. All Rights Reserved.
+ *
+ *   This program is free software; you can redistribute it and/or modify
+ *   it under the terms of version 2 of the GNU General Public License as
+ *   published by the Free Software Foundation.
+ *
+ *   This program is distributed in the hope that 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.
+ *
+ *   BSD LICENSE
+ *
+ *   Copyright (C) 2015 EMC Corporation. All Rights Reserved.
+ *
+ *   Redistribution and use in source and binary forms, with or without
+ *   modification, are permitted provided that the following conditions
+ *   are met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ *       notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above copy
+ *       notice, this list of conditions and the following disclaimer in
+ *       the documentation and/or other materials provided with the
+ *       distribution.
+ *     * Neither the name of Intel Corporation nor the names of its
+ *       contributors may be used to endorse or promote products derived
+ *       from this software without specific prior written permission.
+ *
+ *   THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ *   "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ *   LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ *   A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ *   OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ *   SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ *   LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ *   DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ *   THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ *   (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ *   OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ * PCIe NTB Pingpong Linux driver
+ *
+ * Contact Information:
+ * Allen Hubbe <Allen.Hubbe@emc.com>
+ */
+
+/* Note: load this module with option 'dyndbg=+p' */
+
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+
+#include <linux/dma-mapping.h>
+#include <linux/pci.h>
+#include <linux/slab.h>
+#include <linux/spinlock.h>
+
+#include <linux/ntb.h>
+
+#define DRIVER_NAME			"ntb_pingpong"
+#define DRIVER_DESCRIPTION		"PCIe NTB Simple Pingpong Client"
+
+#define DRIVER_LICENSE			"Dual BSD/GPL"
+#define DRIVER_VERSION			"1.0"
+#define DRIVER_RELDATE			"24 March 2015"
+#define DRIVER_AUTHOR			"Allen Hubbe <Allen.Hubbe@emc.com>"
+
+MODULE_LICENSE(DRIVER_LICENSE);
+MODULE_VERSION(DRIVER_VERSION);
+MODULE_AUTHOR(DRIVER_AUTHOR);
+MODULE_DESCRIPTION(DRIVER_DESCRIPTION);
+
+static unsigned int unsafe;
+module_param(unsafe, uint, 0644);
+MODULE_PARM_DESC(unsafe, "Run even though ntb operations may be unsafe");
+
+static unsigned int delay_ms = 1000;
+module_param(delay_ms, uint, 0644);
+MODULE_PARM_DESC(delay_ms, "Milliseconds to delay the response to peer");
+
+static unsigned long db_init = 0x7;
+module_param(db_init, ulong, 0644);
+MODULE_PARM_DESC(delay_ms, "Initial doorbell bits to ring on the peer");
+
+struct pp_ctx {
+	struct ntb_dev			*ntb;
+	u64				db_bits;
+	/* synchronize access to db_bits by ping and pong */
+	spinlock_t			db_lock;
+	struct timer_list		db_timer;
+	unsigned long			db_delay;
+};
+
+static void pp_ping(unsigned long ctx)
+{
+	struct pp_ctx *pp = (void *)ctx;
+	unsigned long irqflags;
+	u64 db_bits, db_mask;
+	u32 spad_rd, spad_wr;
+
+	spin_lock_irqsave(&pp->db_lock, irqflags);
+	{
+		db_mask = ntb_db_valid_mask(pp->ntb);
+		db_bits = ntb_db_read(pp->ntb);
+
+		if (db_bits) {
+			dev_dbg(&pp->ntb->dev,
+				"Masked pongs %#llx\n",
+				db_bits);
+			ntb_db_clear(pp->ntb, db_bits);
+		}
+
+		db_bits = ((pp->db_bits | db_bits) << 1) & db_mask;
+
+		if (!db_bits)
+			db_bits = db_init;
+
+		spad_rd = ntb_spad_read(pp->ntb, 0);
+		spad_wr = spad_rd + 1;
+
+		dev_dbg(&pp->ntb->dev,
+			"Ping bits %#llx read %#x write %#x\n",
+			db_bits, spad_rd, spad_wr);
+
+		ntb_peer_spad_write(pp->ntb, 0, spad_wr);
+		ntb_peer_db_set(pp->ntb, db_bits);
+		ntb_db_clear_mask(pp->ntb, db_mask);
+
+		pp->db_bits = 0;
+	}
+	spin_unlock_irqrestore(&pp->db_lock, irqflags);
+}
+
+static void pp_link_event(void *ctx)
+{
+	struct pp_ctx *pp = ctx;
+
+	if (ntb_link_is_up(pp->ntb, NULL, NULL) == 1) {
+		dev_dbg(&pp->ntb->dev, "link is up\n");
+		pp_ping((unsigned long)pp);
+	} else {
+		dev_dbg(&pp->ntb->dev, "link is down\n");
+		del_timer(&pp->db_timer);
+	}
+}
+
+static void pp_db_event(void *ctx, int vec)
+{
+	struct pp_ctx *pp = ctx;
+	u64 db_bits, db_mask;
+	unsigned long irqflags;
+
+	spin_lock_irqsave(&pp->db_lock, irqflags);
+	{
+		db_mask = ntb_db_vector_mask(pp->ntb, vec);
+		db_bits = db_mask & ntb_db_read(pp->ntb);
+		ntb_db_set_mask(pp->ntb, db_mask);
+		ntb_db_clear(pp->ntb, db_bits);
+
+		pp->db_bits |= db_bits;
+
+		mod_timer(&pp->db_timer, jiffies + pp->db_delay);
+
+		dev_dbg(&pp->ntb->dev,
+			"Pong vec %d bits %#llx\n",
+			vec, db_bits);
+	}
+	spin_unlock_irqrestore(&pp->db_lock, irqflags);
+}
+
+static const struct ntb_ctx_ops pp_ops = {
+	.link_event = pp_link_event,
+	.db_event = pp_db_event,
+};
+
+static int pp_probe(struct ntb_client *client,
+		    struct ntb_dev *ntb)
+{
+	struct pp_ctx *pp;
+	int rc;
+
+	if (ntb_db_is_unsafe(ntb)) {
+		dev_dbg(&ntb->dev, "doorbell is unsafe\n");
+		if (!unsafe) {
+			rc = -EINVAL;
+			goto err_pp;
+		}
+	}
+
+	if (ntb_spad_is_unsafe(ntb)) {
+		dev_dbg(&ntb->dev, "scratchpad is unsafe\n");
+		if (!unsafe) {
+			rc = -EINVAL;
+			goto err_pp;
+		}
+	}
+
+	pp = kmalloc(sizeof(*pp), GFP_KERNEL);
+	if (!pp) {
+		rc = -ENOMEM;
+		goto err_pp;
+	}
+
+	pp->ntb = ntb;
+	pp->db_bits = 0;
+	spin_lock_init(&pp->db_lock);
+	setup_timer(&pp->db_timer, pp_ping, (unsigned long)pp);
+	pp->db_delay = msecs_to_jiffies(delay_ms);
+
+	rc = ntb_set_ctx(ntb, pp, &pp_ops);
+	if (rc)
+		goto err_ctx;
+
+	ntb_link_enable(ntb, NTB_SPEED_AUTO, NTB_WIDTH_AUTO);
+	ntb_link_event(ntb);
+
+	return 0;
+
+err_ctx:
+	kfree(pp);
+err_pp:
+	return rc;
+}
+
+static void pp_remove(struct ntb_client *client,
+		      struct ntb_dev *ntb)
+{
+	struct pp_ctx *pp = ntb->ctx;
+
+	ntb_clear_ctx(ntb);
+	del_timer_sync(&pp->db_timer);
+	ntb_link_disable(ntb);
+
+	kfree(pp);
+}
+
+static struct ntb_client pp_client = {
+	.ops = {
+		.probe = pp_probe,
+		.remove = pp_remove,
+	},
+};
+module_ntb_client(pp_client);