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. There are two important files located. First
  20is the 'run' node that controls run and stop phases of the test, and the second
  21one, 'results', is used to get the test case results.
  22
  23Note that in this case test will not run on load automatically.
  24
  25Example of usage:
  26        % echo dma0chan0 > /sys/module/dmatest/parameters/channel
  27        % echo 2000 > /sys/module/dmatest/parameters/timeout
  28        % echo 1 > /sys/module/dmatest/parameters/iterations
  29        % echo 1 > /sys/kernel/debug/dmatest/run
  30
  31Hint: available channel list could be extracted by running the following
  32command:
  33        % ls -1 /sys/class/dma/
  34
  35After a while you will start to get messages about current status or error like
  36in the original code.
  37
  38Note that running a new test will not stop any in progress test.
  39
  40The following command should return actual state of the test.
  41        % cat /sys/kernel/debug/dmatest/run
  42
  43To wait for test done the user may perform a busy loop that checks the state.
  44
  45        % while [ $(cat /sys/kernel/debug/dmatest/run) = "Y" ]
  46        > do
  47        >       echo -n "."
  48        >       sleep 1
  49        > done
  50        > echo
  51
  52        Part 3 - When built-in in the kernel...
  53
  54The module parameters that is supplied to the kernel command line will be used
  55for the first performed test. After user gets a control, the test could be
  56re-run with the same or different parameters. For the details see the above
  57section "Part 2 - When dmatest is built as a module..."
  58
  59In both cases the module parameters are used as the actual values for the test
  60case. You always could check them at run-time by running
  61        % grep -H . /sys/module/dmatest/parameters/*
  62
  63        Part 4 - Gathering the test results
  64
  65The module provides a storage for the test results in the memory. The gathered
  66data could be used after test is done.
  67
  68The special file 'results' in the debugfs represents gathered data of the in
  69progress test. The messages collected are printed to the kernel log as well.
  70
  71Example of output:
  72        % cat /sys/kernel/debug/dmatest/results
  73        dma0chan0-copy0: #1: No errors with src_off=0x7bf dst_off=0x8ad len=0x3fea (0)
  74
  75The message format is unified across the different types of errors. A number in
  76the parens represents additional information, e.g. error code, error counter,
  77or status.
  78
  79Comparison between buffers is stored to the dedicated structure.
  80
  81Note that the verify result is now accessible only via file 'results' in the
  82debugfs.
  83
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