Documentation/dmatest.txt

   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 should return actual state of the test.
  43         % cat /sys/kernel/debug/dmatest/run
  44
  45 To wait for test done the user may perform a busy loop that checks the state.
  46
  47         % while [ $(cat /sys/module/dmatest/parameters/run) = "Y" ]
  48         > do
  49         >       echo -n "."
  50         >       sleep 1
  51         > done
  52         > echo
  53
  54         Part 3 - When built-in in the kernel...
  55
  56 The module parameters that is supplied to the kernel command line will be used
  57 for the first performed test. After user gets a control, the test could be
  58 re-run with the same or different parameters. For the details see the above
  59 section "Part 2 - When dmatest is built as a module..."
  60
  61 In both cases the module parameters are used as the actual values for the test
  62 case. You always could check them at run-time by running
  63         % grep -H . /sys/module/dmatest/parameters/*
  64
  65         Part 4 - Gathering the test results
  66
  67 Test results are printed to the kernel log buffer with the format:
  68
  69 "dmatest: result <channel>: <test id>: '<error msg>' with src_off=<val> dst_off=<val> len=<val> (<err code>)"
  70
  71 Example of output:
  72         % dmesg | tail -n 1
  73         dmatest: result dma0chan0-copy0: #1: No errors with src_off=0x7bf dst_off=0x8ad len=0x3fea (0)
  74
  75 The message format is unified across the different types of errors. A number in
  76 the parens represents additional information, e.g. error code, error counter,
  77 or status.  A test thread also emits a summary line at completion listing the
  78 number of tests executed, number that failed, and a result code.
  79
  80 Example:
  81         % dmesg | tail -n 1
  82         dmatest: dma3chan0-copy0: summary 400000 tests, 0 failures iops: 61524 KB/s 246098 (0)
  83
  84 The details of a data miscompare error are also emitted, but do not follow the
  85 above format.