| 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. |