1==============
2DMA Test Guide
3==============
4
5Andy Shevchenko <andriy.shevchenko@linux.intel.com>
6
7This small document introduces how to test DMA drivers using dmatest module.
8
9Part 1 - How to build the test module
10=====================================
11
12The menuconfig contains an option that could be found by following path:
13	Device Drivers -> DMA Engine support -> DMA Test client
14
15In the configuration file the option called CONFIG_DMATEST. The dmatest could
16be built as module or inside kernel. Let's consider those cases.
17
18Part 2 - When dmatest is built as a module
19==========================================
20
21Example of usage: ::
22
23    % modprobe dmatest channel=dma0chan0 timeout=2000 iterations=1 run=1
24
25...or: ::
26
27    % modprobe dmatest
28    % echo dma0chan0 > /sys/module/dmatest/parameters/channel
29    % echo 2000 > /sys/module/dmatest/parameters/timeout
30    % echo 1 > /sys/module/dmatest/parameters/iterations
31    % echo 1 > /sys/module/dmatest/parameters/run
32
33...or on the kernel command line: ::
34
35    dmatest.channel=dma0chan0 dmatest.timeout=2000 dmatest.iterations=1 dmatest.run=1
36
37..hint:: available channel list could be extracted by running the following
38         command:
39
40::
41
42    % ls -1 /sys/class/dma/
43
44Once started a message like "dmatest: Started 1 threads using dma0chan0" is
45emitted. After that only test failure messages are reported until the test
46stops.
47
48Note that running a new test will not stop any in progress test.
49
50The following command returns the state of the test. ::
51
52    % cat /sys/module/dmatest/parameters/run
53
54To wait for test completion userpace can poll 'run' until it is false, or use
55the wait parameter. Specifying 'wait=1' when loading the module causes module
56initialization to pause until a test run has completed, while reading
57/sys/module/dmatest/parameters/wait waits for any running test to complete
58before returning. For example, the following scripts wait for 42 tests
59to complete before exiting. Note that if 'iterations' is set to 'infinite' then
60waiting is disabled.
61
62Example: ::
63
64    % modprobe dmatest run=1 iterations=42 wait=1
65    % modprobe -r dmatest
66
67...or: ::
68
69    % modprobe dmatest run=1 iterations=42
70    % cat /sys/module/dmatest/parameters/wait
71    % modprobe -r dmatest
72
73Part 3 - When built-in in the kernel
74====================================
75
76The module parameters that is supplied to the kernel command line will be used
77for the first performed test. After user gets a control, the test could be
78re-run with the same or different parameters. For the details see the above
79section "Part 2 - When dmatest is built as a module..."
80
81In both cases the module parameters are used as the actual values for the test
82case. You always could check them at run-time by running ::
83
84    % grep -H . /sys/module/dmatest/parameters/*
85
86Part 4 - Gathering the test results
87===================================
88
89Test results are printed to the kernel log buffer with the format: ::
90
91    "dmatest: result <channel>: <test id>: '<error msg>' with src_off=<val> dst_off=<val> len=<val> (<err code>)"
92
93Example of output: ::
94
95
96    % dmesg | tail -n 1
97    dmatest: result dma0chan0-copy0: #1: No errors with src_off=0x7bf dst_off=0x8ad len=0x3fea (0)
98
99The message format is unified across the different types of errors. A number in
100the parens represents additional information, e.g. error code, error counter,
101or status. A test thread also emits a summary line at completion listing the
102number of tests executed, number that failed, and a result code.
103
104Example: ::
105
106    % dmesg | tail -n 1
107    dmatest: dma0chan0-copy0: summary 1 test, 0 failures 1000 iops 100000 KB/s (0)
108
109The details of a data miscompare error are also emitted, but do not follow the
110above format.
111