1 .. SPDX-License-Identifier: GPL-2.0
2
3 =========
4 SAS Layer
5 =========
6
7 The SAS Layer is a management infrastructure which manages
8 SAS LLDDs. It sits between SCSI Core and SAS LLDDs. The
9 layout is as follows: while SCSI Core is concerned with
10 SAM/SPC issues, and a SAS LLDD+sequencer is concerned with
11 phy/OOB/link management, the SAS layer is concerned with:
12
13 * SAS Phy/Port/HA event management (LLDD generates,
14 SAS Layer processes),
15 * SAS Port management (creation/destruction),
16 * SAS Domain discovery and revalidation,
17 * SAS Domain device management,
18 * SCSI Host registration/unregistration,
19 * Device registration with SCSI Core (SAS) or libata
20 (SATA), and
21 * Expander management and exporting expander control
22 to user space.
23
24 A SAS LLDD is a PCI device driver. It is concerned with
25 phy/OOB management, and vendor specific tasks and generates
26 events to the SAS layer.
27
28 The SAS Layer does most SAS tasks as outlined in the SAS 1.1
29 spec.
30
31 The sas_ha_struct describes the SAS LLDD to the SAS layer.
32 Most of it is used by the SAS Layer but a few fields need to
33 be initialized by the LLDDs.
34
35 After initializing your hardware, from the probe() function
36 you call sas_register_ha(). It will register your LLDD with
37 the SCSI subsystem, creating a SCSI host and it will
38 register your SAS driver with the sysfs SAS tree it creates.
39 It will then return. Then you enable your phys to actually
40 start OOB (at which point your driver will start calling the
41 notify_* event callbacks).
42
43 Structure descriptions
44 ======================
45
46 ``struct sas_phy``
47 ------------------
48
49 Normally this is statically embedded to your driver's
50 phy structure::
51
52 struct my_phy {
53 blah;
54 struct sas_phy sas_phy;
55 bleh;
56 };
57
58 And then all the phys are an array of my_phy in your HA
59 struct (shown below).
60
61 Then as you go along and initialize your phys you also
62 initialize the sas_phy struct, along with your own
63 phy structure.
64
65 In general, the phys are managed by the LLDD and the ports
66 are managed by the SAS layer. So the phys are initialized
67 and updated by the LLDD and the ports are initialized and
68 updated by the SAS layer.
69
70 There is a scheme where the LLDD can RW certain fields,
71 and the SAS layer can only read such ones, and vice versa.
72 The idea is to avoid unnecessary locking.
73
74 enabled
75 - must be set (0/1)
76
77 id
78 - must be set [0,MAX_PHYS)]
79
80 class, proto, type, role, oob_mode, linkrate
81 - must be set
82
83 oob_mode
84 - you set this when OOB has finished and then notify
85 the SAS Layer.
86
87 sas_addr
88 - this normally points to an array holding the sas
89 address of the phy, possibly somewhere in your my_phy
90 struct.
91
92 attached_sas_addr
93 - set this when you (LLDD) receive an
94 IDENTIFY frame or a FIS frame, _before_ notifying the SAS
95 layer. The idea is that sometimes the LLDD may want to fake
96 or provide a different SAS address on that phy/port and this
97 allows it to do this. At best you should copy the sas
98 address from the IDENTIFY frame or maybe generate a SAS
99 address for SATA directly attached devices. The Discover
100 process may later change this.
101
102 frame_rcvd
103 - this is where you copy the IDENTIFY/FIS frame
104 when you get it; you lock, copy, set frame_rcvd_size and
105 unlock the lock, and then call the event. It is a pointer
106 since there's no way to know your hw frame size _exactly_,
107 so you define the actual array in your phy struct and let
108 this pointer point to it. You copy the frame from your
109 DMAable memory to that area holding the lock.
110
111 sas_prim
112 - this is where primitives go when they're
113 received. See sas.h. Grab the lock, set the primitive,
114 release the lock, notify.
115
116 port
117 - this points to the sas_port if the phy belongs
118 to a port -- the LLDD only reads this. It points to the
119 sas_port this phy is part of. Set by the SAS Layer.
120
121 ha
122 - may be set; the SAS layer sets it anyway.
123
124 lldd_phy
125 - you should set this to point to your phy so you
126 can find your way around faster when the SAS layer calls one
127 of your callbacks and passes you a phy. If the sas_phy is
128 embedded you can also use container_of -- whatever you
129 prefer.
130
131
132 ``struct sas_port``
133 -------------------
134
135 The LLDD doesn't set any fields of this struct -- it only
136 reads them. They should be self explanatory.
137
138 phy_mask is 32 bit, this should be enough for now, as I
139 haven't heard of a HA having more than 8 phys.
140
141 lldd_port
142 - I haven't found use for that -- maybe other
143 LLDD who wish to have internal port representation can make
144 use of this.
145
146 ``struct sas_ha_struct``
147 ------------------------
148
149 It normally is statically declared in your own LLDD
150 structure describing your adapter::
151
152 struct my_sas_ha {
153 blah;
154 struct sas_ha_struct sas_ha;
155 struct my_phy phys[MAX_PHYS];
156 struct sas_port sas_ports[MAX_PHYS]; /* (1) */
157 bleh;
158 };
159
160 (1) If your LLDD doesn't have its own port representation.
161
162 What needs to be initialized (sample function given below).
163
164 pcidev
165 ^^^^^^
166
167 sas_addr
168 - since the SAS layer doesn't want to mess with
169 memory allocation, etc, this points to statically
170 allocated array somewhere (say in your host adapter
171 structure) and holds the SAS address of the host
172 adapter as given by you or the manufacturer, etc.
173
174 sas_port
175 ^^^^^^^^
176
177 sas_phy
178 - an array of pointers to structures. (see
179 note above on sas_addr).
180 These must be set. See more notes below.
181
182 num_phys
183 - the number of phys present in the sas_phy array,
184 and the number of ports present in the sas_port
185 array. There can be a maximum num_phys ports (one per
186 port) so we drop the num_ports, and only use
187 num_phys.
188
189 The event interface::
190
191 /* LLDD calls these to notify the class of an event. */
192 void sas_notify_port_event(struct sas_phy *, enum port_event, gfp_t);
193 void sas_notify_phy_event(struct sas_phy *, enum phy_event, gfp_t);
194
195 The port notification::
196
197 /* The class calls these to notify the LLDD of an event. */
198 void (*lldd_port_formed)(struct sas_phy *);
199 void (*lldd_port_deformed)(struct sas_phy *);
200
201 If the LLDD wants notification when a port has been formed
202 or deformed it sets those to a function satisfying the type.
203
204 A SAS LLDD should also implement at least one of the Task
205 Management Functions (TMFs) described in SAM::
206
207 /* Task Management Functions. Must be called from process context. */
208 int (*lldd_abort_task)(struct sas_task *);
209 int (*lldd_abort_task_set)(struct domain_device *, u8 *lun);
210 int (*lldd_clear_task_set)(struct domain_device *, u8 *lun);
211 int (*lldd_I_T_nexus_reset)(struct domain_device *);
212 int (*lldd_lu_reset)(struct domain_device *, u8 *lun);
213 int (*lldd_query_task)(struct sas_task *);
214
215 For more information please read SAM from T10.org.
216
217 Port and Adapter management::
218
219 /* Port and Adapter management */
220 int (*lldd_clear_nexus_port)(struct sas_port *);
221 int (*lldd_clear_nexus_ha)(struct sas_ha_struct *);
222
223 A SAS LLDD should implement at least one of those.
224
225 Phy management::
226
227 /* Phy management */
228 int (*lldd_control_phy)(struct sas_phy *, enum phy_func);
229
230 lldd_ha
231 - set this to point to your HA struct. You can also
232 use container_of if you embedded it as shown above.
233
234 A sample initialization and registration function
235 can look like this (called last thing from probe())
236 *but* before you enable the phys to do OOB::
237
238 static int register_sas_ha(struct my_sas_ha *my_ha)
239 {
240 int i;
241 static struct sas_phy *sas_phys[MAX_PHYS];
242 static struct sas_port *sas_ports[MAX_PHYS];
243
244 my_ha->sas_ha.sas_addr = &my_ha->sas_addr[0];
245
246 for (i = 0; i < MAX_PHYS; i++) {
247 sas_phys[i] = &my_ha->phys[i].sas_phy;
248 sas_ports[i] = &my_ha->sas_ports[i];
249 }
250
251 my_ha->sas_ha.sas_phy = sas_phys;
252 my_ha->sas_ha.sas_port = sas_ports;
253 my_ha->sas_ha.num_phys = MAX_PHYS;
254
255 my_ha->sas_ha.lldd_port_formed = my_port_formed;
256
257 my_ha->sas_ha.lldd_dev_found = my_dev_found;
258 my_ha->sas_ha.lldd_dev_gone = my_dev_gone;
259
260 my_ha->sas_ha.lldd_execute_task = my_execute_task;
261
262 my_ha->sas_ha.lldd_abort_task = my_abort_task;
263 my_ha->sas_ha.lldd_abort_task_set = my_abort_task_set;
264 my_ha->sas_ha.lldd_clear_task_set = my_clear_task_set;
265 my_ha->sas_ha.lldd_I_T_nexus_reset= NULL; (2)
266 my_ha->sas_ha.lldd_lu_reset = my_lu_reset;
267 my_ha->sas_ha.lldd_query_task = my_query_task;
268
269 my_ha->sas_ha.lldd_clear_nexus_port = my_clear_nexus_port;
270 my_ha->sas_ha.lldd_clear_nexus_ha = my_clear_nexus_ha;
271
272 my_ha->sas_ha.lldd_control_phy = my_control_phy;
273
274 return sas_register_ha(&my_ha->sas_ha);
275 }
276
277 (2) SAS 1.1 does not define I_T Nexus Reset TMF.
278
279 Events
280 ======
281
282 Events are **the only way** a SAS LLDD notifies the SAS layer
283 of anything. There is no other method or way a LLDD to tell
284 the SAS layer of anything happening internally or in the SAS
285 domain.
286
287 Phy events::
288
289 PHYE_LOSS_OF_SIGNAL, (C)
290 PHYE_OOB_DONE,
291 PHYE_OOB_ERROR, (C)
292 PHYE_SPINUP_HOLD.
293
294 Port events, passed on a _phy_::
295
296 PORTE_BYTES_DMAED, (M)
297 PORTE_BROADCAST_RCVD, (E)
298 PORTE_LINK_RESET_ERR, (C)
299 PORTE_TIMER_EVENT, (C)
300 PORTE_HARD_RESET.
301
302 Host Adapter event:
303 HAE_RESET
304
305 A SAS LLDD should be able to generate
306
307 - at least one event from group C (choice),
308 - events marked M (mandatory) are mandatory (only one),
309 - events marked E (expander) if it wants the SAS layer
310 to handle domain revalidation (only one such).
311 - Unmarked events are optional.
312
313 Meaning:
314
315 HAE_RESET
316 - when your HA got internal error and was reset.
317
318 PORTE_BYTES_DMAED
319 - on receiving an IDENTIFY/FIS frame
320
321 PORTE_BROADCAST_RCVD
322 - on receiving a primitive
323
324 PORTE_LINK_RESET_ERR
325 - timer expired, loss of signal, loss of DWS, etc. [1]_
326
327 PORTE_TIMER_EVENT
328 - DWS reset timeout timer expired [1]_
329
330 PORTE_HARD_RESET
331 - Hard Reset primitive received.
332
333 PHYE_LOSS_OF_SIGNAL
334 - the device is gone [1]_
335
336 PHYE_OOB_DONE
337 - OOB went fine and oob_mode is valid
338
339 PHYE_OOB_ERROR
340 - Error while doing OOB, the device probably
341 got disconnected. [1]_
342
343 PHYE_SPINUP_HOLD
344 - SATA is present, COMWAKE not sent.
345
346 .. [1] should set/clear the appropriate fields in the phy,
347 or alternatively call the inlined sas_phy_disconnected()
348 which is just a helper, from their tasklet.
349
350 The Execute Command SCSI RPC::
351
352 int (*lldd_execute_task)(struct sas_task *, gfp_t gfp_flags);
353
354 Used to queue a task to the SAS LLDD. @task is the task to be executed.
355 @gfp_mask is the gfp_mask defining the context of the caller.
356
357 This function should implement the Execute Command SCSI RPC,
358
359 That is, when lldd_execute_task() is called, the command
360 go out on the transport *immediately*. There is *no*
361 queuing of any sort and at any level in a SAS LLDD.
362
363 Returns:
364
365 * -SAS_QUEUE_FULL, -ENOMEM, nothing was queued;
366 * 0, the task(s) were queued.
367
368 ::
369
370 struct sas_task {
371 dev -- the device this task is destined to
372 task_proto -- _one_ of enum sas_proto
373 scatter -- pointer to scatter gather list array
374 num_scatter -- number of elements in scatter
375 total_xfer_len -- total number of bytes expected to be transferred
376 data_dir -- PCI_DMA_...
377 task_done -- callback when the task has finished execution
378 };
379
380 Discovery
381 =========
382
383 The sysfs tree has the following purposes:
384
385 a) It shows you the physical layout of the SAS domain at
386 the current time, i.e. how the domain looks in the
387 physical world right now.
388 b) Shows some device parameters _at_discovery_time_.
389
390 This is a link to the tree(1) program, very useful in
391 viewing the SAS domain:
392 ftp://mama.indstate.edu/linux/tree/
393
394 I expect user space applications to actually create a
395 graphical interface of this.
396
397 That is, the sysfs domain tree doesn't show or keep state if
398 you e.g., change the meaning of the READY LED MEANING
399 setting, but it does show you the current connection status
400 of the domain device.
401
402 Keeping internal device state changes is responsibility of
403 upper layers (Command set drivers) and user space.
404
405 When a device or devices are unplugged from the domain, this
406 is reflected in the sysfs tree immediately, and the device(s)
407 removed from the system.
408
409 The structure domain_device describes any device in the SAS
410 domain. It is completely managed by the SAS layer. A task
411 points to a domain device, this is how the SAS LLDD knows
412 where to send the task(s) to. A SAS LLDD only reads the
413 contents of the domain_device structure, but it never creates
414 or destroys one.
415
416 Expander management from User Space
417 ===================================
418
419 In each expander directory in sysfs, there is a file called
420 "smp_portal". It is a binary sysfs attribute file, which
421 implements an SMP portal (Note: this is *NOT* an SMP port),
422 to which user space applications can send SMP requests and
423 receive SMP responses.
424
425 Functionality is deceptively simple:
426
427 1. Build the SMP frame you want to send. The format and layout
428 is described in the SAS spec. Leave the CRC field equal 0.
429
430 open(2)
431
432 2. Open the expander's SMP portal sysfs file in RW mode.
433
434 write(2)
435
436 3. Write the frame you built in 1.
437
438 read(2)
439
440 4. Read the amount of data you expect to receive for the frame you built.
441 If you receive different amount of data you expected to receive,
442 then there was some kind of error.
443
444 close(2)
445
446 All this process is shown in detail in the function do_smp_func()
447 and its callers, in the file "expander_conf.c".
448
449 The kernel functionality is implemented in the file
450 "sas_expander.c".
451
452 The program "expander_conf.c" implements this. It takes one
453 argument, the sysfs file name of the SMP portal to the
454 expander, and gives expander information, including routing
455 tables.
456
457 The SMP portal gives you complete control of the expander,
458 so please be careful.
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