DMA Test Guide
  				==============
  
  		Andy Shevchenko <andriy.shevchenko@linux.intel.com>
  
  This small document introduces how to test DMA drivers using dmatest module.
  
  	Part 1 - How to build the test module
  
  The menuconfig contains an option that could be found by following path:
  	Device Drivers -> DMA Engine support -> DMA Test client
  
  In the configuration file the option called CONFIG_DMATEST. The dmatest could
  be built as module or inside kernel. Let's consider those cases.
  
  	Part 2 - When dmatest is built as a module...
  
  After mounting debugfs and loading the module, the /sys/kernel/debug/dmatest

  folder with nodes will be created. There are two important files located. First
  is the 'run' node that controls run and stop phases of the test, and the second
  one, 'results', is used to get the test case results.

  
  Note that in this case test will not run on load automatically.
  
  Example of usage:

  	% echo dma0chan0 > /sys/module/dmatest/parameters/channel
  	% echo 2000 > /sys/module/dmatest/parameters/timeout
  	% echo 1 > /sys/module/dmatest/parameters/iterations

  	% echo 1 > /sys/kernel/debug/dmatest/run
  
  Hint: available channel list could be extracted by running the following
  command:
  	% ls -1 /sys/class/dma/
  
  After a while you will start to get messages about current status or error like
  in the original code.

  Note that running a new test will not stop any in progress test.

  The following command should return actual state of the test.
  	% cat /sys/kernel/debug/dmatest/run
  
  To wait for test done the user may perform a busy loop that checks the state.
  
  	% while [ $(cat /sys/kernel/debug/dmatest/run) = "Y" ]
  	> do
  	> 	echo -n "."
  	> 	sleep 1
  	> done
  	> echo

  	Part 3 - When built-in in the kernel...
  
  The module parameters that is supplied to the kernel command line will be used
  for the first performed test. After user gets a control, the test could be

  re-run with the same or different parameters. For the details see the above
  section "Part 2 - When dmatest is built as a module..."

  In both cases the module parameters are used as the actual values for the test
  case. You always could check them at run-time by running

  	% grep -H . /sys/module/dmatest/parameters/*

  
  	Part 4 - Gathering the test results
  
  The module provides a storage for the test results in the memory. The gathered
  data could be used after test is done.
  
  The special file 'results' in the debugfs represents gathered data of the in
  progress test. The messages collected are printed to the kernel log as well.
  
  Example of output:
  	% cat /sys/kernel/debug/dmatest/results
  	dma0chan0-copy0: #1: No errors with src_off=0x7bf dst_off=0x8ad len=0x3fea (0)
  
  The message format is unified across the different types of errors. A number in
  the parens represents additional information, e.g. error code, error counter,
  or status.

  Comparison between buffers is stored to the dedicated structure.
  
  Note that the verify result is now accessible only via file 'results' in the
  debugfs.