linux/Documentation/dmatest.txt
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   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
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