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-rw-r--r--Documentation/trace/mmiotrace.txt26
1 files changed, 13 insertions, 13 deletions
diff --git a/Documentation/trace/mmiotrace.txt b/Documentation/trace/mmiotrace.txt
index 5731c67abc55..162effbfbdec 100644
--- a/Documentation/trace/mmiotrace.txt
+++ b/Documentation/trace/mmiotrace.txt
@@ -32,41 +32,41 @@ is no way to automatically detect if you are losing events due to CPUs racing.
32Usage Quick Reference 32Usage Quick Reference
33--------------------- 33---------------------
34 34
35$ mount -t debugfs debugfs /debug 35$ mount -t debugfs debugfs /sys/kernel/debug
36$ echo mmiotrace > /debug/tracing/current_tracer 36$ echo mmiotrace > /sys/kernel/debug/tracing/current_tracer
37$ cat /debug/tracing/trace_pipe > mydump.txt & 37$ cat /sys/kernel/debug/tracing/trace_pipe > mydump.txt &
38Start X or whatever. 38Start X or whatever.
39$ echo "X is up" > /debug/tracing/trace_marker 39$ echo "X is up" > /sys/kernel/debug/tracing/trace_marker
40$ echo nop > /debug/tracing/current_tracer 40$ echo nop > /sys/kernel/debug/tracing/current_tracer
41Check for lost events. 41Check for lost events.
42 42
43 43
44Usage 44Usage
45----- 45-----
46 46
47Make sure debugfs is mounted to /debug. If not, (requires root privileges) 47Make sure debugfs is mounted to /sys/kernel/debug. If not, (requires root privileges)
48$ mount -t debugfs debugfs /debug 48$ mount -t debugfs debugfs /sys/kernel/debug
49 49
50Check that the driver you are about to trace is not loaded. 50Check that the driver you are about to trace is not loaded.
51 51
52Activate mmiotrace (requires root privileges): 52Activate mmiotrace (requires root privileges):
53$ echo mmiotrace > /debug/tracing/current_tracer 53$ echo mmiotrace > /sys/kernel/debug/tracing/current_tracer
54 54
55Start storing the trace: 55Start storing the trace:
56$ cat /debug/tracing/trace_pipe > mydump.txt & 56$ cat /sys/kernel/debug/tracing/trace_pipe > mydump.txt &
57The 'cat' process should stay running (sleeping) in the background. 57The 'cat' process should stay running (sleeping) in the background.
58 58
59Load the driver you want to trace and use it. Mmiotrace will only catch MMIO 59Load the driver you want to trace and use it. Mmiotrace will only catch MMIO
60accesses to areas that are ioremapped while mmiotrace is active. 60accesses to areas that are ioremapped while mmiotrace is active.
61 61
62During tracing you can place comments (markers) into the trace by 62During tracing you can place comments (markers) into the trace by
63$ echo "X is up" > /debug/tracing/trace_marker 63$ echo "X is up" > /sys/kernel/debug/tracing/trace_marker
64This makes it easier to see which part of the (huge) trace corresponds to 64This makes it easier to see which part of the (huge) trace corresponds to
65which action. It is recommended to place descriptive markers about what you 65which action. It is recommended to place descriptive markers about what you
66do. 66do.
67 67
68Shut down mmiotrace (requires root privileges): 68Shut down mmiotrace (requires root privileges):
69$ echo nop > /debug/tracing/current_tracer 69$ echo nop > /sys/kernel/debug/tracing/current_tracer
70The 'cat' process exits. If it does not, kill it by issuing 'fg' command and 70The 'cat' process exits. If it does not, kill it by issuing 'fg' command and
71pressing ctrl+c. 71pressing ctrl+c.
72 72
@@ -78,10 +78,10 @@ to view your kernel log and look for "mmiotrace has lost events" warning. If
78events were lost, the trace is incomplete. You should enlarge the buffers and 78events were lost, the trace is incomplete. You should enlarge the buffers and
79try again. Buffers are enlarged by first seeing how large the current buffers 79try again. Buffers are enlarged by first seeing how large the current buffers
80are: 80are:
81$ cat /debug/tracing/buffer_size_kb 81$ cat /sys/kernel/debug/tracing/buffer_size_kb
82gives you a number. Approximately double this number and write it back, for 82gives you a number. Approximately double this number and write it back, for
83instance: 83instance:
84$ echo 128000 > /debug/tracing/buffer_size_kb 84$ echo 128000 > /sys/kernel/debug/tracing/buffer_size_kb
85Then start again from the top. 85Then start again from the top.
86 86
87If you are doing a trace for a driver project, e.g. Nouveau, you should also 87If you are doing a trace for a driver project, e.g. Nouveau, you should also