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Andy Shevchenko851b7e12013-03-04 11:09:30 +02001 DMA Test Guide
2 ==============
3
4 Andy Shevchenko <andriy.shevchenko@linux.intel.com>
5
6This small document introduces how to test DMA drivers using dmatest module.
7
8 Part 1 - How to build the test module
9
10The menuconfig contains an option that could be found by following path:
11 Device Drivers -> DMA Engine support -> DMA Test client
12
13In the configuration file the option called CONFIG_DMATEST. The dmatest could
14be built as module or inside kernel. Let's consider those cases.
15
16 Part 2 - When dmatest is built as a module...
17
18After mounting debugfs and loading the module, the /sys/kernel/debug/dmatest
19folder with nodes will be created. They are the same as module parameters with
20addition of the 'run' node that controls run and stop phases of the test.
21
22Note that in this case test will not run on load automatically.
23
24Example of usage:
25 % echo dma0chan0 > /sys/kernel/debug/dmatest/channel
26 % echo 2000 > /sys/kernel/debug/dmatest/timeout
27 % echo 1 > /sys/kernel/debug/dmatest/iterations
28 % echo 1 > /sys/kernel/debug/dmatest/run
29
30Hint: available channel list could be extracted by running the following
31command:
32 % ls -1 /sys/class/dma/
33
34After a while you will start to get messages about current status or error like
35in the original code.
36
Andy Shevchenkobcc567e2013-05-23 14:29:53 +030037Note that running a new test will not stop any in progress test.
Andy Shevchenko851b7e12013-03-04 11:09:30 +020038
Andy Shevchenko3e5ccd82013-03-04 11:09:31 +020039The following command should return actual state of the test.
40 % cat /sys/kernel/debug/dmatest/run
41
42To wait for test done the user may perform a busy loop that checks the state.
43
44 % while [ $(cat /sys/kernel/debug/dmatest/run) = "Y" ]
45 > do
46 > echo -n "."
47 > sleep 1
48 > done
49 > echo
50
Andy Shevchenko851b7e12013-03-04 11:09:30 +020051 Part 3 - When built-in in the kernel...
52
53The module parameters that is supplied to the kernel command line will be used
54for the first performed test. After user gets a control, the test could be
Andy Shevchenkobcc567e2013-05-23 14:29:53 +030055re-run with the same or different parameters. For the details see the above
56section "Part 2 - When dmatest is built as a module..."
Andy Shevchenko851b7e12013-03-04 11:09:30 +020057
58In both cases the module parameters are used as initial values for the test case.
59You always could check them at run-time by running
60 % grep -H . /sys/module/dmatest/parameters/*
Andy Shevchenko95019c82013-03-04 11:09:33 +020061
62 Part 4 - Gathering the test results
63
64The module provides a storage for the test results in the memory. The gathered
65data could be used after test is done.
66
67The special file 'results' in the debugfs represents gathered data of the in
68progress test. The messages collected are printed to the kernel log as well.
69
70Example of output:
71 % cat /sys/kernel/debug/dmatest/results
72 dma0chan0-copy0: #1: No errors with src_off=0x7bf dst_off=0x8ad len=0x3fea (0)
73
74The message format is unified across the different types of errors. A number in
75the parens represents additional information, e.g. error code, error counter,
76or status.
77
Andy Shevchenkod86b2f22013-03-04 11:09:34 +020078Comparison between buffers is stored to the dedicated structure.
79
80Note that the verify result is now accessible only via file 'results' in the
81debugfs.