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