drivers/platform/surface/surface_aggregator_hub.c

   1 // SPDX-License-Identifier: GPL-2.0+
   2 /*
   3  * Driver for Surface System Aggregator Module (SSAM) subsystem device hubs.
   4  *
   5  * Provides a driver for SSAM subsystems device hubs. This driver performs
   6  * instantiation of the devices managed by said hubs and takes care of
   7  * (hot-)removal.
   8  *
   9  * Copyright (C) 2020-2022 Maximilian Luz <luzmaximilian@gmail.com>
  10  */
  11
  12 #include <linux/kernel.h>
  13 #include <linux/limits.h>
  14 #include <linux/module.h>
  15 #include <linux/types.h>
  16 #include <linux/workqueue.h>
  17
  18 #include <linux/surface_aggregator/device.h>
  19
  20
  21 /* -- SSAM generic subsystem hub driver framework. -------------------------- */
  22
  23 enum ssam_hub_state {
  24         SSAM_HUB_UNINITIALIZED,         /* Only set during initialization. */
  25         SSAM_HUB_CONNECTED,
  26         SSAM_HUB_DISCONNECTED,
  27 };
  28
  29 enum ssam_hub_flags {
  30         SSAM_HUB_HOT_REMOVED,
  31 };
  32
  33 struct ssam_hub;
  34
  35 struct ssam_hub_ops {
  36         int (*get_state)(struct ssam_hub *hub, enum ssam_hub_state *state);
  37 };
  38
  39 struct ssam_hub {
  40         struct ssam_device *sdev;
  41
  42         enum ssam_hub_state state;
  43         unsigned long flags;
  44
  45         struct delayed_work update_work;
  46         unsigned long connect_delay;
  47
  48         struct ssam_event_notifier notif;
  49         struct ssam_hub_ops ops;
  50 };
  51
  52 struct ssam_hub_desc {
  53         struct {
  54                 struct ssam_event_registry reg;
  55                 struct ssam_event_id id;
  56                 enum ssam_event_mask mask;
  57         } event;
  58
  59         struct {
  60                 u32 (*notify)(struct ssam_event_notifier *nf, const struct ssam_event *event);
  61                 int (*get_state)(struct ssam_hub *hub, enum ssam_hub_state *state);
  62         } ops;
  63
  64         unsigned long connect_delay_ms;
  65 };
  66
  67 static void ssam_hub_update_workfn(struct work_struct *work)
  68 {
  69         struct ssam_hub *hub = container_of(work, struct ssam_hub, update_work.work);
  70         enum ssam_hub_state state;
  71         int status = 0;
  72
  73         status = hub->ops.get_state(hub, &state);
  74         if (status)
  75                 return;
  76
  77         /*
  78          * There is a small possibility that hub devices were hot-removed and
  79          * re-added before we were able to remove them here. In that case, both
  80          * the state returned by get_state() and the state of the hub will
  81          * equal SSAM_HUB_CONNECTED and we would bail early below, which would
  82          * leave child devices without proper (re-)initialization and the
  83          * hot-remove flag set.
  84          *
  85          * Therefore, we check whether devices have been hot-removed via an
  86          * additional flag on the hub and, in this case, override the returned
  87          * hub state. In case of a missed disconnect (i.e. get_state returned
  88          * "connected"), we further need to re-schedule this work (with the
  89          * appropriate delay) as the actual connect work submission might have
  90          * been merged with this one.
  91          *
  92          * This then leads to one of two cases: Either we submit an unnecessary
  93          * work item (which will get ignored via either the queue or the state
  94          * checks) or, in the unlikely case that the work is actually required,
  95          * double the normal connect delay.
  96          */
  97         if (test_and_clear_bit(SSAM_HUB_HOT_REMOVED, &hub->flags)) {
  98                 if (state == SSAM_HUB_CONNECTED)
  99                         schedule_delayed_work(&hub->update_work, hub->connect_delay);
 100
 101                 state = SSAM_HUB_DISCONNECTED;
 102         }
 103
 104         if (hub->state == state)
 105                 return;
 106         hub->state = state;
 107
 108         if (hub->state == SSAM_HUB_CONNECTED)
 109                 status = ssam_device_register_clients(hub->sdev);
 110         else
 111                 ssam_remove_clients(&hub->sdev->dev);
 112
 113         if (status)
 114                 dev_err(&hub->sdev->dev, "failed to update hub child devices: %d\n", status);
 115 }
 116
 117 static int ssam_hub_mark_hot_removed(struct device *dev, void *_data)
 118 {
 119         struct ssam_device *sdev = to_ssam_device(dev);
 120
 121         if (is_ssam_device(dev))
 122                 ssam_device_mark_hot_removed(sdev);
 123
 124         return 0;
 125 }
 126
 127 static void ssam_hub_update(struct ssam_hub *hub, bool connected)
 128 {
 129         unsigned long delay;
 130
 131         /* Mark devices as hot-removed before we remove any. */
 132         if (!connected) {
 133                 set_bit(SSAM_HUB_HOT_REMOVED, &hub->flags);
 134                 device_for_each_child_reverse(&hub->sdev->dev, NULL, ssam_hub_mark_hot_removed);
 135         }
 136
 137         /*
 138          * Delay update when the base/keyboard cover is being connected to give
 139          * devices/EC some time to set up.
 140          */
 141         delay = connected ? hub->connect_delay : 0;
 142
 143         schedule_delayed_work(&hub->update_work, delay);
 144 }
 145
 146 static int __maybe_unused ssam_hub_resume(struct device *dev)
 147 {
 148         struct ssam_hub *hub = dev_get_drvdata(dev);
 149
 150         schedule_delayed_work(&hub->update_work, 0);
 151         return 0;
 152 }
 153 static SIMPLE_DEV_PM_OPS(ssam_hub_pm_ops, NULL, ssam_hub_resume);
 154
 155 static int ssam_hub_probe(struct ssam_device *sdev)
 156 {
 157         const struct ssam_hub_desc *desc;
 158         struct ssam_hub *hub;
 159         int status;
 160
 161         desc = ssam_device_get_match_data(sdev);
 162         if (!desc) {
 163                 WARN(1, "no driver match data specified");
 164                 return -EINVAL;
 165         }
 166
 167         hub = devm_kzalloc(&sdev->dev, sizeof(*hub), GFP_KERNEL);
 168         if (!hub)
 169                 return -ENOMEM;
 170
 171         hub->sdev = sdev;
 172         hub->state = SSAM_HUB_UNINITIALIZED;
 173
 174         hub->notif.base.priority = INT_MAX;  /* This notifier should run first. */
 175         hub->notif.base.fn = desc->ops.notify;
 176         hub->notif.event.reg = desc->event.reg;
 177         hub->notif.event.id = desc->event.id;
 178         hub->notif.event.mask = desc->event.mask;
 179         hub->notif.event.flags = SSAM_EVENT_SEQUENCED;
 180
 181         hub->connect_delay = msecs_to_jiffies(desc->connect_delay_ms);
 182         hub->ops.get_state = desc->ops.get_state;
 183
 184         INIT_DELAYED_WORK(&hub->update_work, ssam_hub_update_workfn);
 185
 186         ssam_device_set_drvdata(sdev, hub);
 187
 188         status = ssam_device_notifier_register(sdev, &hub->notif);
 189         if (status)
 190                 return status;
 191
 192         schedule_delayed_work(&hub->update_work, 0);
 193         return 0;
 194 }
 195
 196 static void ssam_hub_remove(struct ssam_device *sdev)
 197 {
 198         struct ssam_hub *hub = ssam_device_get_drvdata(sdev);
 199
 200         ssam_device_notifier_unregister(sdev, &hub->notif);
 201         cancel_delayed_work_sync(&hub->update_work);
 202         ssam_remove_clients(&sdev->dev);
 203 }
 204
 205
 206 /* -- SSAM base-subsystem hub driver. --------------------------------------- */
 207
 208 /*
 209  * Some devices (especially battery) may need a bit of time to be fully usable
 210  * after being (re-)connected. This delay has been determined via
 211  * experimentation.
 212  */
 213 #define SSAM_BASE_UPDATE_CONNECT_DELAY          2500
 214
 215 SSAM_DEFINE_SYNC_REQUEST_R(ssam_bas_query_opmode, u8, {
 216         .target_category = SSAM_SSH_TC_BAS,
 217         .target_id       = SSAM_SSH_TID_SAM,
 218         .command_id      = 0x0d,
 219         .instance_id     = 0x00,
 220 });
 221
 222 #define SSAM_BAS_OPMODE_TABLET          0x00
 223 #define SSAM_EVENT_BAS_CID_CONNECTION   0x0c
 224
 225 static int ssam_base_hub_query_state(struct ssam_hub *hub, enum ssam_hub_state *state)
 226 {
 227         u8 opmode;
 228         int status;
 229
 230         status = ssam_retry(ssam_bas_query_opmode, hub->sdev->ctrl, &opmode);
 231         if (status < 0) {
 232                 dev_err(&hub->sdev->dev, "failed to query base state: %d\n", status);
 233                 return status;
 234         }
 235
 236         if (opmode != SSAM_BAS_OPMODE_TABLET)
 237                 *state = SSAM_HUB_CONNECTED;
 238         else
 239                 *state = SSAM_HUB_DISCONNECTED;
 240
 241         return 0;
 242 }
 243
 244 static u32 ssam_base_hub_notif(struct ssam_event_notifier *nf, const struct ssam_event *event)
 245 {
 246         struct ssam_hub *hub = container_of(nf, struct ssam_hub, notif);
 247
 248         if (event->command_id != SSAM_EVENT_BAS_CID_CONNECTION)
 249                 return 0;
 250
 251         if (event->length < 1) {
 252                 dev_err(&hub->sdev->dev, "unexpected payload size: %u\n", event->length);
 253                 return 0;
 254         }
 255
 256         ssam_hub_update(hub, event->data[0]);
 257
 258         /*
 259          * Do not return SSAM_NOTIF_HANDLED: The event should be picked up and
 260          * consumed by the detachment system driver. We're just a (more or less)
 261          * silent observer.
 262          */
 263         return 0;
 264 }
 265
 266 static const struct ssam_hub_desc base_hub = {
 267         .event = {
 268                 .reg = SSAM_EVENT_REGISTRY_SAM,
 269                 .id = {
 270                         .target_category = SSAM_SSH_TC_BAS,
 271                         .instance = 0,
 272                 },
 273                 .mask = SSAM_EVENT_MASK_NONE,
 274         },
 275         .ops = {
 276                 .notify = ssam_base_hub_notif,
 277                 .get_state = ssam_base_hub_query_state,
 278         },
 279         .connect_delay_ms = SSAM_BASE_UPDATE_CONNECT_DELAY,
 280 };
 281
 282
 283 /* -- SSAM KIP-subsystem hub driver. ---------------------------------------- */
 284
 285 /*
 286  * Some devices may need a bit of time to be fully usable after being
 287  * (re-)connected. This delay has been determined via experimentation.
 288  */
 289 #define SSAM_KIP_UPDATE_CONNECT_DELAY           250
 290
 291 #define SSAM_EVENT_KIP_CID_CONNECTION           0x2c
 292
 293 SSAM_DEFINE_SYNC_REQUEST_R(__ssam_kip_query_state, u8, {
 294         .target_category = SSAM_SSH_TC_KIP,
 295         .target_id       = SSAM_SSH_TID_SAM,
 296         .command_id      = 0x2c,
 297         .instance_id     = 0x00,
 298 });
 299
 300 static int ssam_kip_hub_query_state(struct ssam_hub *hub, enum ssam_hub_state *state)
 301 {
 302         int status;
 303         u8 connected;
 304
 305         status = ssam_retry(__ssam_kip_query_state, hub->sdev->ctrl, &connected);
 306         if (status < 0) {
 307                 dev_err(&hub->sdev->dev, "failed to query KIP connection state: %d\n", status);
 308                 return status;
 309         }
 310
 311         *state = connected ? SSAM_HUB_CONNECTED : SSAM_HUB_DISCONNECTED;
 312         return 0;
 313 }
 314
 315 static u32 ssam_kip_hub_notif(struct ssam_event_notifier *nf, const struct ssam_event *event)
 316 {
 317         struct ssam_hub *hub = container_of(nf, struct ssam_hub, notif);
 318
 319         if (event->command_id != SSAM_EVENT_KIP_CID_CONNECTION)
 320                 return 0;       /* Return "unhandled". */
 321
 322         if (event->length < 1) {
 323                 dev_err(&hub->sdev->dev, "unexpected payload size: %u\n", event->length);
 324                 return 0;
 325         }
 326
 327         ssam_hub_update(hub, event->data[0]);
 328         return SSAM_NOTIF_HANDLED;
 329 }
 330
 331 static const struct ssam_hub_desc kip_hub = {
 332         .event = {
 333                 .reg = SSAM_EVENT_REGISTRY_SAM,
 334                 .id = {
 335                         .target_category = SSAM_SSH_TC_KIP,
 336                         .instance = 0,
 337                 },
 338                 .mask = SSAM_EVENT_MASK_TARGET,
 339         },
 340         .ops = {
 341                 .notify = ssam_kip_hub_notif,
 342                 .get_state = ssam_kip_hub_query_state,
 343         },
 344         .connect_delay_ms = SSAM_KIP_UPDATE_CONNECT_DELAY,
 345 };
 346
 347
 348 /* -- Driver registration. -------------------------------------------------- */
 349
 350 static const struct ssam_device_id ssam_hub_match[] = {
 351         { SSAM_VDEV(HUB, SAM, SSAM_SSH_TC_KIP, 0x00), (unsigned long)&kip_hub  },
 352         { SSAM_VDEV(HUB, SAM, SSAM_SSH_TC_BAS, 0x00), (unsigned long)&base_hub },
 353         { }
 354 };
 355 MODULE_DEVICE_TABLE(ssam, ssam_hub_match);
 356
 357 static struct ssam_device_driver ssam_subsystem_hub_driver = {
 358         .probe = ssam_hub_probe,
 359         .remove = ssam_hub_remove,
 360         .match_table = ssam_hub_match,
 361         .driver = {
 362                 .name = "surface_aggregator_subsystem_hub",
 363                 .probe_type = PROBE_PREFER_ASYNCHRONOUS,
 364                 .pm = &ssam_hub_pm_ops,
 365         },
 366 };
 367 module_ssam_device_driver(ssam_subsystem_hub_driver);
 368
 369 MODULE_AUTHOR("Maximilian Luz <luzmaximilian@gmail.com>");
 370 MODULE_DESCRIPTION("Subsystem device hub driver for Surface System Aggregator Module");
 371 MODULE_LICENSE("GPL");