kernel/drivers/misc/mic/scif/scif_peer_bus.c

   1 /*
   2  * Intel MIC Platform Software Stack (MPSS)
   3  *
   4  * Copyright(c) 2014 Intel Corporation.
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License, version 2, as
   8  * published by the Free Software Foundation.
   9  *
  10  * This program is distributed in the hope that it will be useful, but
  11  * WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  13  * General Public License for more details.
  14  *
  15  * Intel SCIF driver.
  16  */
  17 #include "scif_main.h"
  18 #include "../bus/scif_bus.h"
  19 #include "scif_peer_bus.h"
  20
  21 static inline struct scif_peer_dev *
  22 dev_to_scif_peer(struct device *dev)
  23 {
  24         return container_of(dev, struct scif_peer_dev, dev);
  25 }
  26
  27 struct bus_type scif_peer_bus = {
  28         .name  = "scif_peer_bus",
  29 };
  30
  31 static void scif_peer_release_dev(struct device *d)
  32 {
  33         struct scif_peer_dev *sdev = dev_to_scif_peer(d);
  34         struct scif_dev *scifdev = &scif_dev[sdev->dnode];
  35
  36         scif_cleanup_scifdev(scifdev);
  37         kfree(sdev);
  38 }
  39
  40 static int scif_peer_initialize_device(struct scif_dev *scifdev)
  41 {
  42         struct scif_peer_dev *spdev;
  43         int ret;
  44
  45         spdev = kzalloc(sizeof(*spdev), GFP_KERNEL);
  46         if (!spdev) {
  47                 ret = -ENOMEM;
  48                 goto err;
  49         }
  50
  51         spdev->dev.parent = scifdev->sdev->dev.parent;
  52         spdev->dev.release = scif_peer_release_dev;
  53         spdev->dnode = scifdev->node;
  54         spdev->dev.bus = &scif_peer_bus;
  55         dev_set_name(&spdev->dev, "scif_peer-dev%u", spdev->dnode);
  56
  57         device_initialize(&spdev->dev);
  58         get_device(&spdev->dev);
  59         rcu_assign_pointer(scifdev->spdev, spdev);
  60
  61         mutex_lock(&scif_info.conflock);
  62         scif_info.total++;
  63         scif_info.maxid = max_t(u32, spdev->dnode, scif_info.maxid);
  64         mutex_unlock(&scif_info.conflock);
  65         return 0;
  66 err:
  67         dev_err(&scifdev->sdev->dev,
  68                 "dnode %d: initialize_device rc %d\n", scifdev->node, ret);
  69         return ret;
  70 }
  71
  72 static int scif_peer_add_device(struct scif_dev *scifdev)
  73 {
  74         struct scif_peer_dev *spdev = rcu_dereference(scifdev->spdev);
  75         char pool_name[16];
  76         int ret;
  77
  78         ret = device_add(&spdev->dev);
  79         put_device(&spdev->dev);
  80         if (ret) {
  81                 dev_err(&scifdev->sdev->dev,
  82                         "dnode %d: peer device_add failed\n", scifdev->node);
  83                 goto put_spdev;
  84         }
  85
  86         scnprintf(pool_name, sizeof(pool_name), "scif-%d", spdev->dnode);
  87         scifdev->signal_pool = dmam_pool_create(pool_name, &scifdev->sdev->dev,
  88                                                 sizeof(struct scif_status), 1,
  89                                                 0);
  90         if (!scifdev->signal_pool) {
  91                 dev_err(&scifdev->sdev->dev,
  92                         "dnode %d: dmam_pool_create failed\n", scifdev->node);
  93                 ret = -ENOMEM;
  94                 goto del_spdev;
  95         }
  96         dev_dbg(&spdev->dev, "Added peer dnode %d\n", spdev->dnode);
  97         return 0;
  98 del_spdev:
  99         device_del(&spdev->dev);
 100 put_spdev:
 101         RCU_INIT_POINTER(scifdev->spdev, NULL);
 102         synchronize_rcu();
 103         put_device(&spdev->dev);
 104
 105         mutex_lock(&scif_info.conflock);
 106         scif_info.total--;
 107         mutex_unlock(&scif_info.conflock);
 108         return ret;
 109 }
 110
 111 void scif_add_peer_device(struct work_struct *work)
 112 {
 113         struct scif_dev *scifdev = container_of(work, struct scif_dev,
 114                                                 peer_add_work);
 115
 116         scif_peer_add_device(scifdev);
 117 }
 118
 119 /*
 120  * Peer device registration is split into a device_initialize and a device_add.
 121  * The reason for doing this is as follows: First, peer device registration
 122  * itself cannot be done in the message processing thread and must be delegated
 123  * to another workqueue, otherwise if SCIF client probe, called during peer
 124  * device registration, calls scif_connect(..), it will block the message
 125  * processing thread causing a deadlock. Next, device_initialize is done in the
 126  * "top-half" message processing thread and device_add in the "bottom-half"
 127  * workqueue. If this is not done, SCIF_CNCT_REQ message processing executing
 128  * concurrently with SCIF_INIT message processing is unable to get a reference
 129  * on the peer device, thereby failing the connect request.
 130  */
 131 void scif_peer_register_device(struct scif_dev *scifdev)
 132 {
 133         int ret;
 134
 135         mutex_lock(&scifdev->lock);
 136         ret = scif_peer_initialize_device(scifdev);
 137         if (ret)
 138                 goto exit;
 139         schedule_work(&scifdev->peer_add_work);
 140 exit:
 141         mutex_unlock(&scifdev->lock);
 142 }
 143
 144 int scif_peer_unregister_device(struct scif_dev *scifdev)
 145 {
 146         struct scif_peer_dev *spdev;
 147
 148         mutex_lock(&scifdev->lock);
 149         /* Flush work to ensure device register is complete */
 150         flush_work(&scifdev->peer_add_work);
 151
 152         /*
 153          * Continue holding scifdev->lock since theoretically unregister_device
 154          * can be called simultaneously from multiple threads
 155          */
 156         spdev = rcu_dereference(scifdev->spdev);
 157         if (!spdev) {
 158                 mutex_unlock(&scifdev->lock);
 159                 return -ENODEV;
 160         }
 161
 162         RCU_INIT_POINTER(scifdev->spdev, NULL);
 163         synchronize_rcu();
 164         mutex_unlock(&scifdev->lock);
 165
 166         dev_dbg(&spdev->dev, "Removing peer dnode %d\n", spdev->dnode);
 167         device_unregister(&spdev->dev);
 168
 169         mutex_lock(&scif_info.conflock);
 170         scif_info.total--;
 171         mutex_unlock(&scif_info.conflock);
 172         return 0;
 173 }
 174
 175 int scif_peer_bus_init(void)
 176 {
 177         return bus_register(&scif_peer_bus);
 178 }
 179
 180 void scif_peer_bus_exit(void)
 181 {
 182         bus_unregister(&scif_peer_bus);
 183 }