/*
   * 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
  ",
  				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
  ",
  			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
  ");
  		pp_ping((unsigned long)pp);
  	} else {
  		dev_dbg(&pp->ntb->dev, "link is down
  ");
  		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
  ",
  			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
  ");
  		if (!unsafe) {
  			rc = -EINVAL;
  			goto err_pp;
  		}
  	}
  
  	if (ntb_spad_is_unsafe(ntb)) {
  		dev_dbg(&ntb->dev, "scratchpad is unsafe
  ");
  		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);