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1ACPICA Trace Facility
2
3Copyright (C) 2015, Intel Corporation
4Author: Lv Zheng <lv.zheng@intel.com>
5
6
7Abstract:
8
9This document describes the functions and the interfaces of the method
10tracing facility.
11
121. Functionalities and usage examples:
13
14 ACPICA provides method tracing capability. And two functions are
15 currently implemented using this capability.
16
17 A. Log reducer
18 ACPICA subsystem provides debugging outputs when CONFIG_ACPI_DEBUG is
19 enabled. The debugging messages which are deployed via
20 ACPI_DEBUG_PRINT() macro can be reduced at 2 levels - per-component
21 level (known as debug layer, configured via
22 /sys/module/acpi/parameters/debug_layer) and per-type level (known as
23 debug level, configured via /sys/module/acpi/parameters/debug_level).
24
25 But when the particular layer/level is applied to the control method
26 evaluations, the quantity of the debugging outputs may still be too
27 large to be put into the kernel log buffer. The idea thus is worked out
28 to only enable the particular debug layer/level (normally more detailed)
29 logs when the control method evaluation is started, and disable the
30 detailed logging when the control method evaluation is stopped.
31
32 The following command examples illustrate the usage of the "log reducer"
33 functionality:
34 a. Filter out the debug layer/level matched logs when control methods
35 are being evaluated:
36 # cd /sys/module/acpi/parameters
37 # echo "0xXXXXXXXX" > trace_debug_layer
38 # echo "0xYYYYYYYY" > trace_debug_level
39 # echo "enable" > trace_state
40 b. Filter out the debug layer/level matched logs when the specified
41 control method is being evaluated:
42 # cd /sys/module/acpi/parameters
43 # echo "0xXXXXXXXX" > trace_debug_layer
44 # echo "0xYYYYYYYY" > trace_debug_level
45 # echo "\PPPP.AAAA.TTTT.HHHH" > trace_method_name
46 # echo "method" > /sys/module/acpi/parameters/trace_state
47 c. Filter out the debug layer/level matched logs when the specified
48 control method is being evaluated for the first time:
49 # cd /sys/module/acpi/parameters
50 # echo "0xXXXXXXXX" > trace_debug_layer
51 # echo "0xYYYYYYYY" > trace_debug_level
52 # echo "\PPPP.AAAA.TTTT.HHHH" > trace_method_name
53 # echo "method-once" > /sys/module/acpi/parameters/trace_state
54 Where:
55 0xXXXXXXXX/0xYYYYYYYY: Refer to Documentation/acpi/debug.txt for
56 possible debug layer/level masking values.
57 \PPPP.AAAA.TTTT.HHHH: Full path of a control method that can be found
58 in the ACPI namespace. It needn't be an entry
59 of a control method evaluation.
60
61 B. AML tracer
62
63 There are special log entries added by the method tracing facility at
64 the "trace points" the AML interpreter starts/stops to execute a control
65 method, or an AML opcode. Note that the format of the log entries are
66 subject to change:
67 [ 0.186427] exdebug-0398 ex_trace_point : Method Begin [0xf58394d8:\_SB.PCI0.LPCB.ECOK] execution.
68 [ 0.186630] exdebug-0398 ex_trace_point : Opcode Begin [0xf5905c88:If] execution.
69 [ 0.186820] exdebug-0398 ex_trace_point : Opcode Begin [0xf5905cc0:LEqual] execution.
70 [ 0.187010] exdebug-0398 ex_trace_point : Opcode Begin [0xf5905a20:-NamePath-] execution.
71 [ 0.187214] exdebug-0398 ex_trace_point : Opcode End [0xf5905a20:-NamePath-] execution.
72 [ 0.187407] exdebug-0398 ex_trace_point : Opcode Begin [0xf5905f60:One] execution.
73 [ 0.187594] exdebug-0398 ex_trace_point : Opcode End [0xf5905f60:One] execution.
74 [ 0.187789] exdebug-0398 ex_trace_point : Opcode End [0xf5905cc0:LEqual] execution.
75 [ 0.187980] exdebug-0398 ex_trace_point : Opcode Begin [0xf5905cc0:Return] execution.
76 [ 0.188146] exdebug-0398 ex_trace_point : Opcode Begin [0xf5905f60:One] execution.
77 [ 0.188334] exdebug-0398 ex_trace_point : Opcode End [0xf5905f60:One] execution.
78 [ 0.188524] exdebug-0398 ex_trace_point : Opcode End [0xf5905cc0:Return] execution.
79 [ 0.188712] exdebug-0398 ex_trace_point : Opcode End [0xf5905c88:If] execution.
80 [ 0.188903] exdebug-0398 ex_trace_point : Method End [0xf58394d8:\_SB.PCI0.LPCB.ECOK] execution.
81
82 Developers can utilize these special log entries to track the AML
83 interpretion, thus can aid issue debugging and performance tuning. Note
84 that, as the "AML tracer" logs are implemented via ACPI_DEBUG_PRINT()
85 macro, CONFIG_ACPI_DEBUG is also required to be enabled for enabling
86 "AML tracer" logs.
87
88 The following command examples illustrate the usage of the "AML tracer"
89 functionality:
90 a. Filter out the method start/stop "AML tracer" logs when control
91 methods are being evaluated:
92 # cd /sys/module/acpi/parameters
93 # echo "0x80" > trace_debug_layer
94 # echo "0x10" > trace_debug_level
95 # echo "enable" > trace_state
96 b. Filter out the method start/stop "AML tracer" when the specified
97 control method is being evaluated:
98 # cd /sys/module/acpi/parameters
99 # echo "0x80" > trace_debug_layer
100 # echo "0x10" > trace_debug_level
101 # echo "\PPPP.AAAA.TTTT.HHHH" > trace_method_name
102 # echo "method" > trace_state
103 c. Filter out the method start/stop "AML tracer" logs when the specified
104 control method is being evaluated for the first time:
105 # cd /sys/module/acpi/parameters
106 # echo "0x80" > trace_debug_layer
107 # echo "0x10" > trace_debug_level
108 # echo "\PPPP.AAAA.TTTT.HHHH" > trace_method_name
109 # echo "method-once" > trace_state
110 d. Filter out the method/opcode start/stop "AML tracer" when the
111 specified control method is being evaluated:
112 # cd /sys/module/acpi/parameters
113 # echo "0x80" > trace_debug_layer
114 # echo "0x10" > trace_debug_level
115 # echo "\PPPP.AAAA.TTTT.HHHH" > trace_method_name
116 # echo "opcode" > trace_state
117 e. Filter out the method/opcode start/stop "AML tracer" when the
118 specified control method is being evaluated for the first time:
119 # cd /sys/module/acpi/parameters
120 # echo "0x80" > trace_debug_layer
121 # echo "0x10" > trace_debug_level
122 # echo "\PPPP.AAAA.TTTT.HHHH" > trace_method_name
123 # echo "opcode-opcode" > trace_state
124
125 Note that all above method tracing facility related module parameters can
126 be used as the boot parameters, for example:
127 acpi.trace_debug_layer=0x80 acpi.trace_debug_level=0x10 \
128 acpi.trace_method_name=\_SB.LID0._LID acpi.trace_state=opcode-once
129
1302. Interface descriptions:
131
132 All method tracing functions can be configured via ACPI module
133 parameters that are accessible at /sys/module/acpi/parameters/:
134
135 trace_method_name
136 The full path of the AML method that the user wants to trace.
137 Note that the full path shouldn't contain the trailing "_"s in its
138 name segments but may contain "\" to form an absolute path.
139
140 trace_debug_layer
141 The temporary debug_layer used when the tracing feature is enabled.
142 Using ACPI_EXECUTER (0x80) by default, which is the debug_layer
143 used to match all "AML tracer" logs.
144
145 trace_debug_level
146 The temporary debug_level used when the tracing feature is enabled.
147 Using ACPI_LV_TRACE_POINT (0x10) by default, which is the
148 debug_level used to match all "AML tracer" logs.
149
150 trace_state
151 The status of the tracing feature.
152 Users can enable/disable this debug tracing feature by executing
153 the following command:
154 # echo string > /sys/module/acpi/parameters/trace_state
155 Where "string" should be one of the following:
156 "disable"
157 Disable the method tracing feature.
158 "enable"
159 Enable the method tracing feature.
160 ACPICA debugging messages matching
161 "trace_debug_layer/trace_debug_level" during any method
162 execution will be logged.
163 "method"
164 Enable the method tracing feature.
165 ACPICA debugging messages matching
166 "trace_debug_layer/trace_debug_level" during method execution
167 of "trace_method_name" will be logged.
168 "method-once"
169 Enable the method tracing feature.
170 ACPICA debugging messages matching
171 "trace_debug_layer/trace_debug_level" during method execution
172 of "trace_method_name" will be logged only once.
173 "opcode"
174 Enable the method tracing feature.
175 ACPICA debugging messages matching
176 "trace_debug_layer/trace_debug_level" during method/opcode
177 execution of "trace_method_name" will be logged.
178 "opcode-once"
179 Enable the method tracing feature.
180 ACPICA debugging messages matching
181 "trace_debug_layer/trace_debug_level" during method/opcode
182 execution of "trace_method_name" will be logged only once.
183 Note that, the difference between the "enable" and other feature
184 enabling options are:
185 1. When "enable" is specified, since
186 "trace_debug_layer/trace_debug_level" shall apply to all control
187 method evaluations, after configuring "trace_state" to "enable",
188 "trace_method_name" will be reset to NULL.
189 2. When "method/opcode" is specified, if
190 "trace_method_name" is NULL when "trace_state" is configured to
191 these options, the "trace_debug_layer/trace_debug_level" will
192 apply to all control method evaluations.