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
  18After mounting debugfs and loading the module, the /sys/kernel/debug/dmatest
  19folder with nodes will be created. They are the same as module parameters with
  20addition of the 'run' node that controls run and stop phases of the test.
  21
  22Note that in this case test will not run on load automatically.
  23
  24Example of usage:
  25        % echo dma0chan0 > /sys/kernel/debug/dmatest/channel
  26        % echo 2000 > /sys/kernel/debug/dmatest/timeout
  27        % echo 1 > /sys/kernel/debug/dmatest/iterations
  28        % echo 1 > /sys/kernel/debug/dmatest/run
  29
  30Hint: available channel list could be extracted by running the following
  31command:
  32        % ls -1 /sys/class/dma/
  33
  34After a while you will start to get messages about current status or error like
  35in the original code.
  36
  37Note that running a new test will not stop any in progress test.
  38
  39The following command should return actual state of the test.
  40        % cat /sys/kernel/debug/dmatest/run
  41
  42To wait for test done the user may perform a busy loop that checks the state.
  43
  44        % while [ $(cat /sys/kernel/debug/dmatest/run) = "Y" ]
  45        > do
  46        >       echo -n "."
  47        >       sleep 1
  48        > done
  49        > echo
  50
  51        Part 3 - When built-in in the kernel...
  52
  53The module parameters that is supplied to the kernel command line will be used
  54for the first performed test. After user gets a control, the test could be
  55re-run with the same or different parameters. For the details see the above
  56section "Part 2 - When dmatest is built as a module..."
  57
  58In both cases the module parameters are used as initial values for the test case.
  59You always could check them at run-time by running
  60        % grep -H . /sys/module/dmatest/parameters/*
  61
  62        Part 4 - Gathering the test results
  63
  64The module provides a storage for the test results in the memory. The gathered
  65data could be used after test is done.
  66
  67The special file 'results' in the debugfs represents gathered data of the in
  68progress test. The messages collected are printed to the kernel log as well.
  69
  70Example of output:
  71        % cat /sys/kernel/debug/dmatest/results
  72        dma0chan0-copy0: #1: No errors with src_off=0x7bf dst_off=0x8ad len=0x3fea (0)
  73
  74The message format is unified across the different types of errors. A number in
  75the parens represents additional information, e.g. error code, error counter,
  76or status.
  77
  78Comparison between buffers is stored to the dedicated structure.
  79
  80Note that the verify result is now accessible only via file 'results' in the
  81debugfs.
  82
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