iommu/exynos: Add callback for initializing devices from device tree
[sfrench/cifs-2.6.git] / Documentation / ABI / testing / sysfs-devices-system-cpu
1 What:           /sys/devices/system/cpu/
2 Date:           pre-git history
3 Contact:        Linux kernel mailing list <linux-kernel@vger.kernel.org>
4 Description:
5                 A collection of both global and individual CPU attributes
6
7                 Individual CPU attributes are contained in subdirectories
8                 named by the kernel's logical CPU number, e.g.:
9
10                 /sys/devices/system/cpu/cpu#/
11
12 What:           /sys/devices/system/cpu/kernel_max
13                 /sys/devices/system/cpu/offline
14                 /sys/devices/system/cpu/online
15                 /sys/devices/system/cpu/possible
16                 /sys/devices/system/cpu/present
17 Date:           December 2008
18 Contact:        Linux kernel mailing list <linux-kernel@vger.kernel.org>
19 Description:    CPU topology files that describe kernel limits related to
20                 hotplug. Briefly:
21
22                 kernel_max: the maximum cpu index allowed by the kernel
23                 configuration.
24
25                 offline: cpus that are not online because they have been
26                 HOTPLUGGED off or exceed the limit of cpus allowed by the
27                 kernel configuration (kernel_max above).
28
29                 online: cpus that are online and being scheduled.
30
31                 possible: cpus that have been allocated resources and can be
32                 brought online if they are present.
33
34                 present: cpus that have been identified as being present in
35                 the system.
36
37                 See Documentation/cputopology.txt for more information.
38
39
40 What:           /sys/devices/system/cpu/probe
41                 /sys/devices/system/cpu/release
42 Date:           November 2009
43 Contact:        Linux kernel mailing list <linux-kernel@vger.kernel.org>
44 Description:    Dynamic addition and removal of CPU's.  This is not hotplug
45                 removal, this is meant complete removal/addition of the CPU
46                 from the system.
47
48                 probe: writes to this file will dynamically add a CPU to the
49                 system.  Information written to the file to add CPU's is
50                 architecture specific.
51
52                 release: writes to this file dynamically remove a CPU from
53                 the system.  Information writtento the file to remove CPU's
54                 is architecture specific.
55
56 What:           /sys/devices/system/cpu/cpu#/node
57 Date:           October 2009
58 Contact:        Linux memory management mailing list <linux-mm@kvack.org>
59 Description:    Discover NUMA node a CPU belongs to
60
61                 When CONFIG_NUMA is enabled, a symbolic link that points
62                 to the corresponding NUMA node directory.
63
64                 For example, the following symlink is created for cpu42
65                 in NUMA node 2:
66
67                 /sys/devices/system/cpu/cpu42/node2 -> ../../node/node2
68
69
70 What:           /sys/devices/system/cpu/cpu#/topology/core_id
71                 /sys/devices/system/cpu/cpu#/topology/core_siblings
72                 /sys/devices/system/cpu/cpu#/topology/core_siblings_list
73                 /sys/devices/system/cpu/cpu#/topology/physical_package_id
74                 /sys/devices/system/cpu/cpu#/topology/thread_siblings
75                 /sys/devices/system/cpu/cpu#/topology/thread_siblings_list
76 Date:           December 2008
77 Contact:        Linux kernel mailing list <linux-kernel@vger.kernel.org>
78 Description:    CPU topology files that describe a logical CPU's relationship
79                 to other cores and threads in the same physical package.
80
81                 One cpu# directory is created per logical CPU in the system,
82                 e.g. /sys/devices/system/cpu/cpu42/.
83
84                 Briefly, the files above are:
85
86                 core_id: the CPU core ID of cpu#. Typically it is the
87                 hardware platform's identifier (rather than the kernel's).
88                 The actual value is architecture and platform dependent.
89
90                 core_siblings: internal kernel map of cpu#'s hardware threads
91                 within the same physical_package_id.
92
93                 core_siblings_list: human-readable list of the logical CPU
94                 numbers within the same physical_package_id as cpu#.
95
96                 physical_package_id: physical package id of cpu#. Typically
97                 corresponds to a physical socket number, but the actual value
98                 is architecture and platform dependent.
99
100                 thread_siblings: internel kernel map of cpu#'s hardware
101                 threads within the same core as cpu#
102
103                 thread_siblings_list: human-readable list of cpu#'s hardware
104                 threads within the same core as cpu#
105
106                 See Documentation/cputopology.txt for more information.
107
108
109 What:           /sys/devices/system/cpu/cpuidle/current_driver
110                 /sys/devices/system/cpu/cpuidle/current_governer_ro
111 Date:           September 2007
112 Contact:        Linux kernel mailing list <linux-kernel@vger.kernel.org>
113 Description:    Discover cpuidle policy and mechanism
114
115                 Various CPUs today support multiple idle levels that are
116                 differentiated by varying exit latencies and power
117                 consumption during idle.
118
119                 Idle policy (governor) is differentiated from idle mechanism
120                 (driver)
121
122                 current_driver: displays current idle mechanism
123
124                 current_governor_ro: displays current idle policy
125
126                 See files in Documentation/cpuidle/ for more information.
127
128
129 What:           /sys/devices/system/cpu/cpu#/cpufreq/*
130 Date:           pre-git history
131 Contact:        linux-pm@vger.kernel.org
132 Description:    Discover and change clock speed of CPUs
133
134                 Clock scaling allows you to change the clock speed of the
135                 CPUs on the fly. This is a nice method to save battery
136                 power, because the lower the clock speed, the less power
137                 the CPU consumes.
138
139                 There are many knobs to tweak in this directory.
140
141                 See files in Documentation/cpu-freq/ for more information.
142
143                 In particular, read Documentation/cpu-freq/user-guide.txt
144                 to learn how to control the knobs.
145
146
147 What:           /sys/devices/system/cpu/cpu#/cpufreq/freqdomain_cpus
148 Date:           June 2013
149 Contact:        linux-pm@vger.kernel.org
150 Description:    Discover CPUs in the same CPU frequency coordination domain
151
152                 freqdomain_cpus is the list of CPUs (online+offline) that share
153                 the same clock/freq domain (possibly at the hardware level).
154                 That information may be hidden from the cpufreq core and the
155                 value of related_cpus may be different from freqdomain_cpus. This
156                 attribute is useful for user space DVFS controllers to get better
157                 power/performance results for platforms using acpi-cpufreq.
158
159                 This file is only present if the acpi-cpufreq driver is in use.
160
161
162 What:           /sys/devices/system/cpu/cpu*/cache/index3/cache_disable_{0,1}
163 Date:           August 2008
164 KernelVersion:  2.6.27
165 Contact:        discuss@x86-64.org
166 Description:    Disable L3 cache indices
167
168                 These files exist in every CPU's cache/index3 directory. Each
169                 cache_disable_{0,1} file corresponds to one disable slot which
170                 can be used to disable a cache index. Reading from these files
171                 on a processor with this functionality will return the currently
172                 disabled index for that node. There is one L3 structure per
173                 node, or per internal node on MCM machines. Writing a valid
174                 index to one of these files will cause the specificed cache
175                 index to be disabled.
176
177                 All AMD processors with L3 caches provide this functionality.
178                 For details, see BKDGs at
179                 http://developer.amd.com/documentation/guides/Pages/default.aspx
180
181
182 What:           /sys/devices/system/cpu/cpufreq/boost
183 Date:           August 2012
184 Contact:        Linux kernel mailing list <linux-kernel@vger.kernel.org>
185 Description:    Processor frequency boosting control
186
187                 This switch controls the boost setting for the whole system.
188                 Boosting allows the CPU and the firmware to run at a frequency
189                 beyound it's nominal limit.
190                 More details can be found in Documentation/cpu-freq/boost.txt
191
192
193 What:           /sys/devices/system/cpu/cpu#/crash_notes
194                 /sys/devices/system/cpu/cpu#/crash_notes_size
195 Date:           April 2013
196 Contact:        kexec@lists.infradead.org
197 Description:    address and size of the percpu note.
198
199                 crash_notes: the physical address of the memory that holds the
200                 note of cpu#.
201
202                 crash_notes_size: size of the note of cpu#.
203
204
205 What:           /sys/devices/system/cpu/intel_pstate/max_perf_pct
206                 /sys/devices/system/cpu/intel_pstate/min_perf_pct
207                 /sys/devices/system/cpu/intel_pstate/no_turbo
208 Date:           February 2013
209 Contact:        linux-pm@vger.kernel.org
210 Description:    Parameters for the Intel P-state driver
211
212                 Logic for selecting the current P-state in Intel
213                 Sandybridge+ processors. The three knobs control
214                 limits for the P-state that will be requested by the
215                 driver.
216
217                 max_perf_pct: limits the maximum P state that will be requested by
218                 the driver stated as a percentage of the available performance.
219
220                 min_perf_pct: limits the minimum P state that will be requested by
221                 the driver stated as a percentage of the available performance.
222
223                 no_turbo: limits the driver to selecting P states below the turbo
224                 frequency range.
225
226                 More details can be found in Documentation/cpu-freq/intel-pstate.txt
227
228 What:           /sys/devices/system/cpu/cpu*/cache/index*/<set_of_attributes_mentioned_below>
229 Date:           July 2014(documented, existed before August 2008)
230 Contact:        Sudeep Holla <sudeep.holla@arm.com>
231                 Linux kernel mailing list <linux-kernel@vger.kernel.org>
232 Description:    Parameters for the CPU cache attributes
233
234                 allocation_policy:
235                         - WriteAllocate: allocate a memory location to a cache line
236                                          on a cache miss because of a write
237                         - ReadAllocate: allocate a memory location to a cache line
238                                         on a cache miss because of a read
239                         - ReadWriteAllocate: both writeallocate and readallocate
240
241                 attributes: LEGACY used only on IA64 and is same as write_policy
242
243                 coherency_line_size: the minimum amount of data in bytes that gets
244                                      transferred from memory to cache
245
246                 level: the cache hierarcy in the multi-level cache configuration
247
248                 number_of_sets: total number of sets in the cache, a set is a
249                                 collection of cache lines with the same cache index
250
251                 physical_line_partition: number of physical cache line per cache tag
252
253                 shared_cpu_list: the list of logical cpus sharing the cache
254
255                 shared_cpu_map: logical cpu mask containing the list of cpus sharing
256                                 the cache
257
258                 size: the total cache size in kB
259
260                 type:
261                         - Instruction: cache that only holds instructions
262                         - Data: cache that only caches data
263                         - Unified: cache that holds both data and instructions
264
265                 ways_of_associativity: degree of freedom in placing a particular block
266                                         of memory in the cache
267
268                 write_policy:
269                         - WriteThrough: data is written to both the cache line
270                                         and to the block in the lower-level memory
271                         - WriteBack: data is written only to the cache line and
272                                      the modified cache line is written to main
273                                      memory only when it is replaced