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1 | DMA Test Guide |
2 | ============== |
3 | |
4 | Andy Shevchenko <andriy.shevchenko@linux.intel.com> |
5 | |
6 | This small document introduces how to test DMA drivers using dmatest module. |
7 | |
8 | Part 1 - How to build the test module |
9 | |
10 | The menuconfig contains an option that could be found by following path: |
11 | Device Drivers -> DMA Engine support -> DMA Test client |
12 | |
13 | In the configuration file the option called CONFIG_DMATEST. The dmatest could |
14 | be built as module or inside kernel. Let's consider those cases. |
15 | |
16 | Part 2 - When dmatest is built as a module... |
17 | |
18 | Example 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 | |
32 | Hint: available channel list could be extracted by running the following |
33 | command: |
34 | % ls -1 /sys/class/dma/ |
35 | |
36 | Once started a message like "dmatest: Started 1 threads using dma0chan0" is |
37 | emitted. After that only test failure messages are reported until the test |
38 | stops. |
39 | |
40 | Note that running a new test will not stop any in progress test. |
41 | |
42 | The following command returns the state of the test. |
43 | % cat /sys/module/dmatest/parameters/run |
44 | |
45 | To wait for test completion userpace can poll 'run' until it is false, or use |
46 | the wait parameter. Specifying 'wait=1' when loading the module causes module |
47 | initialization to pause until a test run has completed, while reading |
48 | /sys/module/dmatest/parameters/wait waits for any running test to complete |
49 | before returning. For example, the following scripts wait for 42 tests |
50 | to complete before exiting. Note that if 'iterations' is set to 'infinite' then |
51 | waiting is disabled. |
52 | |
53 | Example: |
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 | |
63 | The module parameters that is supplied to the kernel command line will be used |
64 | for the first performed test. After user gets a control, the test could be |
65 | re-run with the same or different parameters. For the details see the above |
66 | section "Part 2 - When dmatest is built as a module..." |
67 | |
68 | In both cases the module parameters are used as the actual values for the test |
69 | case. 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 | |
74 | Test 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 | |
78 | Example 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 | |
82 | The message format is unified across the different types of errors. A number in |
83 | the parens represents additional information, e.g. error code, error counter, |
84 | or status. A test thread also emits a summary line at completion listing the |
85 | number of tests executed, number that failed, and a result code. |
86 | |
87 | Example: |
88 | % dmesg | tail -n 1 |
89 | dmatest: dma0chan0-copy0: summary 1 test, 0 failures 1000 iops 100000 KB/s (0) |
90 | |
91 | The details of a data miscompare error are also emitted, but do not follow the |
92 | above format. |
93 |
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