blob: 28fbd877f85a7971ce446e75278d5cd0f2750318 [file] [log] [blame]
Alexandre Bouninee15b4d62011-03-23 16:43:00 -07001 The Linux RapidIO Subsystem
2
3~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
4
5The RapidIO standard is a packet-based fabric interconnect standard designed for
6use in embedded systems. Development of the RapidIO standard is directed by the
7RapidIO Trade Association (RTA). The current version of the RapidIO specification
8is publicly available for download from the RTA web-site [1].
9
10This document describes the basics of the Linux RapidIO subsystem and provides
11information on its major components.
12
131 Overview
14----------
15
16Because the RapidIO subsystem follows the Linux device model it is integrated
17into the kernel similarly to other buses by defining RapidIO-specific device and
18bus types and registering them within the device model.
19
20The Linux RapidIO subsystem is architecture independent and therefore defines
21architecture-specific interfaces that provide support for common RapidIO
22subsystem operations.
23
242. Core Components
25------------------
26
27A typical RapidIO network is a combination of endpoints and switches.
28Each of these components is represented in the subsystem by an associated data
29structure. The core logical components of the RapidIO subsystem are defined
30in include/linux/rio.h file.
31
322.1 Master Port
33
34A master port (or mport) is a RapidIO interface controller that is local to the
35processor executing the Linux code. A master port generates and receives RapidIO
36packets (transactions). In the RapidIO subsystem each master port is represented
37by a rio_mport data structure. This structure contains master port specific
38resources such as mailboxes and doorbells. The rio_mport also includes a unique
39host device ID that is valid when a master port is configured as an enumerating
40host.
41
42RapidIO master ports are serviced by subsystem specific mport device drivers
43that provide functionality defined for this subsystem. To provide a hardware
44independent interface for RapidIO subsystem operations, rio_mport structure
45includes rio_ops data structure which contains pointers to hardware specific
46implementations of RapidIO functions.
47
482.2 Device
49
50A RapidIO device is any endpoint (other than mport) or switch in the network.
51All devices are presented in the RapidIO subsystem by corresponding rio_dev data
52structure. Devices form one global device list and per-network device lists
53(depending on number of available mports and networks).
54
552.3 Switch
56
57A RapidIO switch is a special class of device that routes packets between its
58ports towards their final destination. The packet destination port within a
59switch is defined by an internal routing table. A switch is presented in the
60RapidIO subsystem by rio_dev data structure expanded by additional rio_switch
61data structure, which contains switch specific information such as copy of the
62routing table and pointers to switch specific functions.
63
64The RapidIO subsystem defines the format and initialization method for subsystem
65specific switch drivers that are designed to provide hardware-specific
66implementation of common switch management routines.
67
682.4 Network
69
70A RapidIO network is a combination of interconnected endpoint and switch devices.
71Each RapidIO network known to the system is represented by corresponding rio_net
72data structure. This structure includes lists of all devices and local master
73ports that form the same network. It also contains a pointer to the default
74master port that is used to communicate with devices within the network.
75
Alexandre Bounineed5edee2013-07-03 15:08:59 -0700762.5 Device Drivers
77
78RapidIO device-specific drivers follow Linux Kernel Driver Model and are
79intended to support specific RapidIO devices attached to the RapidIO network.
80
812.6 Subsystem Interfaces
82
83RapidIO interconnect specification defines features that may be used to provide
84one or more common service layers for all participating RapidIO devices. These
85common services may act separately from device-specific drivers or be used by
86device-specific drivers. Example of such service provider is the RIONET driver
87which implements Ethernet-over-RapidIO interface. Because only one driver can be
88registered for a device, all common RapidIO services have to be registered as
89subsystem interfaces. This allows to have multiple common services attached to
90the same device without blocking attachment of a device-specific driver.
91
Alexandre Bouninee15b4d62011-03-23 16:43:00 -0700923. Subsystem Initialization
93---------------------------
94
95In order to initialize the RapidIO subsystem, a platform must initialize and
96register at least one master port within the RapidIO network. To register mport
Alexandre Bounineed5edee2013-07-03 15:08:59 -070097within the subsystem controller driver's initialization code calls function
Alexandre Bounine5eeb9292013-05-24 15:55:07 -070098rio_register_mport() for each available master port.
Alexandre Bouninee15b4d62011-03-23 16:43:00 -070099
Alexandre Bounine5eeb9292013-05-24 15:55:07 -0700100After all active master ports are registered with a RapidIO subsystem,
101an enumeration and/or discovery routine may be called automatically or
102by user-space command.
Alexandre Bouninee15b4d62011-03-23 16:43:00 -0700103
Alexandre Bounineed5edee2013-07-03 15:08:59 -0700104RapidIO subsystem can be configured to be built as a statically linked or
105modular component of the kernel (see details below).
106
Alexandre Bouninee15b4d62011-03-23 16:43:00 -07001074. Enumeration and Discovery
108----------------------------
109
Alexandre Bounine5eeb9292013-05-24 15:55:07 -07001104.1 Overview
111------------
112
Alexandre Bounineed5edee2013-07-03 15:08:59 -0700113RapidIO subsystem configuration options allow users to build enumeration and
Alexandre Bounine5eeb9292013-05-24 15:55:07 -0700114discovery methods as statically linked components or loadable modules.
115An enumeration/discovery method implementation and available input parameters
116define how any given method can be attached to available RapidIO mports:
117simply to all available mports OR individually to the specified mport device.
118
119Depending on selected enumeration/discovery build configuration, there are
120several methods to initiate an enumeration and/or discovery process:
121
122 (a) Statically linked enumeration and discovery process can be started
123 automatically during kernel initialization time using corresponding module
124 parameters. This was the original method used since introduction of RapidIO
125 subsystem. Now this method relies on enumerator module parameter which is
126 'rio-scan.scan' for existing basic enumeration/discovery method.
127 When automatic start of enumeration/discovery is used a user has to ensure
128 that all discovering endpoints are started before the enumerating endpoint
129 and are waiting for enumeration to be completed.
130 Configuration option CONFIG_RAPIDIO_DISC_TIMEOUT defines time that discovering
131 endpoint waits for enumeration to be completed. If the specified timeout
132 expires the discovery process is terminated without obtaining RapidIO network
133 information. NOTE: a timed out discovery process may be restarted later using
Alexandre Bounineed5edee2013-07-03 15:08:59 -0700134 a user-space command as it is described below (if the given endpoint was
135 enumerated successfully).
Alexandre Bounine5eeb9292013-05-24 15:55:07 -0700136
137 (b) Statically linked enumeration and discovery process can be started by
138 a command from user space. This initiation method provides more flexibility
139 for a system startup compared to the option (a) above. After all participating
140 endpoints have been successfully booted, an enumeration process shall be
141 started first by issuing a user-space command, after an enumeration is
142 completed a discovery process can be started on all remaining endpoints.
143
144 (c) Modular enumeration and discovery process can be started by a command from
145 user space. After an enumeration/discovery module is loaded, a network scan
146 process can be started by issuing a user-space command.
147 Similar to the option (b) above, an enumerator has to be started first.
148
149 (d) Modular enumeration and discovery process can be started by a module
150 initialization routine. In this case an enumerating module shall be loaded
151 first.
152
153When a network scan process is started it calls an enumeration or discovery
154routine depending on the configured role of a master port: host or agent.
Alexandre Bouninee15b4d62011-03-23 16:43:00 -0700155
156Enumeration is performed by a master port if it is configured as a host port by
Alexandre Bounineed5edee2013-07-03 15:08:59 -0700157assigning a host destination ID greater than or equal to zero. The host
158destination ID can be assigned to a master port using various methods depending
159on RapidIO subsystem build configuration:
160
161 (a) For a statically linked RapidIO subsystem core use command line parameter
162 "rapidio.hdid=" with a list of destination ID assignments in order of mport
163 device registration. For example, in a system with two RapidIO controllers
164 the command line parameter "rapidio.hdid=-1,7" will result in assignment of
165 the host destination ID=7 to the second RapidIO controller, while the first
166 one will be assigned destination ID=-1.
167
168 (b) If the RapidIO subsystem core is built as a loadable module, in addition
169 to the method shown above, the host destination ID(s) can be specified using
170 traditional methods of passing module parameter "hdid=" during its loading:
171 - from command line: "modprobe rapidio hdid=-1,7", or
172 - from modprobe configuration file using configuration command "options",
173 like in this example: "options rapidio hdid=-1,7". An example of modprobe
174 configuration file is provided in the section below.
175
176 NOTES:
177 (i) if "hdid=" parameter is omitted all available mport will be assigned
178 destination ID = -1;
179 (ii) the "hdid=" parameter in systems with multiple mports can have
180 destination ID assignments omitted from the end of list (default = -1).
181
182If the host device ID for a specific master port is set to -1, the discovery
183process will be performed for it.
Alexandre Bouninee15b4d62011-03-23 16:43:00 -0700184
185The enumeration and discovery routines use RapidIO maintenance transactions
186to access the configuration space of devices.
187
Alexandre Bounineed5edee2013-07-03 15:08:59 -0700188NOTE: If RapidIO switch-specific device drivers are built as loadable modules
189they must be loaded before enumeration/discovery process starts.
190This requirement is cased by the fact that enumeration/discovery methods invoke
191vendor-specific callbacks on early stages.
192
Alexandre Bounine5eeb9292013-05-24 15:55:07 -07001934.2 Automatic Start of Enumeration and Discovery
194------------------------------------------------
195
196Automatic enumeration/discovery start method is applicable only to built-in
197enumeration/discovery RapidIO configuration selection. To enable automatic
198enumeration/discovery start by existing basic enumerator method set use boot
199command line parameter "rio-scan.scan=1".
200
201This configuration requires synchronized start of all RapidIO endpoints that
202form a network which will be enumerated/discovered. Discovering endpoints have
203to be started before an enumeration starts to ensure that all RapidIO
204controllers have been initialized and are ready to be discovered. Configuration
205parameter CONFIG_RAPIDIO_DISC_TIMEOUT defines time (in seconds) which
206a discovering endpoint will wait for enumeration to be completed.
207
208When automatic enumeration/discovery start is selected, basic method's
209initialization routine calls rio_init_mports() to perform enumeration or
210discovery for all known mport devices.
211
212Depending on RapidIO network size and configuration this automatic
213enumeration/discovery start method may be difficult to use due to the
214requirement for synchronized start of all endpoints.
215
2164.3 User-space Start of Enumeration and Discovery
217-------------------------------------------------
218
219User-space start of enumeration and discovery can be used with built-in and
220modular build configurations. For user-space controlled start RapidIO subsystem
221creates the sysfs write-only attribute file '/sys/bus/rapidio/scan'. To initiate
222an enumeration or discovery process on specific mport device, a user needs to
223write mport_ID (not RapidIO destination ID) into that file. The mport_ID is a
224sequential number (0 ... RIO_MAX_MPORTS) assigned during mport device
225registration. For example for machine with single RapidIO controller, mport_ID
226for that controller always will be 0.
227
228To initiate RapidIO enumeration/discovery on all available mports a user may
229write '-1' (or RIO_MPORT_ANY) into the scan attribute file.
230
2314.4 Basic Enumeration Method
232----------------------------
233
234This is an original enumeration/discovery method which is available since
235first release of RapidIO subsystem code. The enumeration process is
236implemented according to the enumeration algorithm outlined in the RapidIO
237Interconnect Specification: Annex I [1].
238
239This method can be configured as statically linked or loadable module.
240The method's single parameter "scan" allows to trigger the enumeration/discovery
241process from module initialization routine.
242
243This enumeration/discovery method can be started only once and does not support
244unloading if it is built as a module.
Alexandre Bouninee15b4d62011-03-23 16:43:00 -0700245
246The enumeration process traverses the network using a recursive depth-first
247algorithm. When a new device is found, the enumerator takes ownership of that
248device by writing into the Host Device ID Lock CSR. It does this to ensure that
249the enumerator has exclusive right to enumerate the device. If device ownership
250is successfully acquired, the enumerator allocates a new rio_dev structure and
251initializes it according to device capabilities.
252
253If the device is an endpoint, a unique device ID is assigned to it and its value
254is written into the device's Base Device ID CSR.
255
256If the device is a switch, the enumerator allocates an additional rio_switch
257structure to store switch specific information. Then the switch's vendor ID and
258device ID are queried against a table of known RapidIO switches. Each switch
259table entry contains a pointer to a switch-specific initialization routine that
260initializes pointers to the rest of switch specific operations, and performs
261hardware initialization if necessary. A RapidIO switch does not have a unique
262device ID; it relies on hopcount and routing for device ID of an attached
263endpoint if access to its configuration registers is required. If a switch (or
264chain of switches) does not have any endpoint (except enumerator) attached to
265it, a fake device ID will be assigned to configure a route to that switch.
266In the case of a chain of switches without endpoint, one fake device ID is used
267to configure a route through the entire chain and switches are differentiated by
268their hopcount value.
269
270For both endpoints and switches the enumerator writes a unique component tag
271into device's Component Tag CSR. That unique value is used by the error
272management notification mechanism to identify a device that is reporting an
273error management event.
274
275Enumeration beyond a switch is completed by iterating over each active egress
276port of that switch. For each active link, a route to a default device ID
277(0xFF for 8-bit systems and 0xFFFF for 16-bit systems) is temporarily written
278into the routing table. The algorithm recurs by calling itself with hopcount + 1
279and the default device ID in order to access the device on the active port.
280
281After the host has completed enumeration of the entire network it releases
282devices by clearing device ID locks (calls rio_clear_locks()). For each endpoint
Alexandre Bounine088024b2011-11-02 13:39:19 -0700283in the system, it sets the Discovered bit in the Port General Control CSR
Alexandre Bouninee15b4d62011-03-23 16:43:00 -0700284to indicate that enumeration is completed and agents are allowed to execute
285passive discovery of the network.
286
287The discovery process is performed by agents and is similar to the enumeration
288process that is described above. However, the discovery process is performed
289without changes to the existing routing because agents only gather information
290about RapidIO network structure and are building an internal map of discovered
291devices. This way each Linux-based component of the RapidIO subsystem has
292a complete view of the network. The discovery process can be performed
293simultaneously by several agents. After initializing its RapidIO master port
294each agent waits for enumeration completion by the host for the configured wait
295time period. If this wait time period expires before enumeration is completed,
296an agent skips RapidIO discovery and continues with remaining kernel
297initialization.
298
Alexandre Bounine5eeb9292013-05-24 15:55:07 -07002994.5 Adding New Enumeration/Discovery Method
300-------------------------------------------
301
302RapidIO subsystem code organization allows addition of new enumeration/discovery
Masanari Iidac9f3f2d2013-07-18 01:29:12 +0900303methods as new configuration options without significant impact to the core
Alexandre Bounine5eeb9292013-05-24 15:55:07 -0700304RapidIO code.
305
306A new enumeration/discovery method has to be attached to one or more mport
307devices before an enumeration/discovery process can be started. Normally,
308method's module initialization routine calls rio_register_scan() to attach
309an enumerator to a specified mport device (or devices). The basic enumerator
310implementation demonstrates this process.
311
Alexandre Bounineed5edee2013-07-03 15:08:59 -07003124.6 Using Loadable RapidIO Switch Drivers
313-----------------------------------------
314
315In the case when RapidIO switch drivers are built as loadable modules a user
316must ensure that they are loaded before the enumeration/discovery starts.
317This process can be automated by specifying pre- or post- dependencies in the
318RapidIO-specific modprobe configuration file as shown in the example below.
319
320 File /etc/modprobe.d/rapidio.conf:
321 ----------------------------------
322
323 # Configure RapidIO subsystem modules
324
325 # Set enumerator host destination ID (overrides kernel command line option)
326 options rapidio hdid=-1,2
327
328 # Load RapidIO switch drivers immediately after rapidio core module was loaded
329 softdep rapidio post: idt_gen2 idtcps tsi57x
330
331 # OR :
332
333 # Load RapidIO switch drivers just before rio-scan enumerator module is loaded
334 softdep rio-scan pre: idt_gen2 idtcps tsi57x
335
336 --------------------------
337
338NOTE: In the example above, one of "softdep" commands must be removed or
339commented out to keep required module loading sequence.
340
341A. References
Alexandre Bouninee15b4d62011-03-23 16:43:00 -0700342-------------
343
344[1] RapidIO Trade Association. RapidIO Interconnect Specifications.
345 http://www.rapidio.org.
346[2] Rapidio TA. Technology Comparisons.
347 http://www.rapidio.org/education/technology_comparisons/
348[3] RapidIO support for Linux.
349 http://lwn.net/Articles/139118/
350[4] Matt Porter. RapidIO for Linux. Ottawa Linux Symposium, 2005
351 http://www.kernel.org/doc/ols/2005/ols2005v2-pages-43-56.pdf