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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 a file named 'run' nodes will be created. 'run' controls run and
stop phases of the test.
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/
Once started a message like "dmatest: Started 1 threads using dma0chan0" is
emitted. After that only test failure messages are reported until the test
stops.
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
Test results are printed to the kernel log buffer with the format:
"dmatest: result <channel>: <test id>: '<error msg>' with src_off=<val> dst_off=<val> len=<val> (<err code>)"
Example of output:
% dmesg | tail -n 1
dmatest: result 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. A test thread also emits a summary line at completion listing the
number of tests executed, number that failed, and a result code.
The details of a data miscompare error are also emitted, but do not follow the
above format.
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