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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...
Example of usage:
% modprobe dmatest channel=dma0chan0 timeout=2000 iterations=1 run=1
...or:
% modprobe dmatest
% echo dma0chan0 > /sys/module/dmatest/parameters/channel
% echo 2000 > /sys/module/dmatest/parameters/timeout
% echo 1 > /sys/module/dmatest/parameters/iterations
% echo 1 > /sys/module/dmatest/parameters/run
...or on the kernel command line:
dmatest.channel=dma0chan0 dmatest.timeout=2000 dmatest.iterations=1 dmatest.run=1
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/module/dmatest/parameters/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.
Example:
% dmesg | tail -n 1
dmatest: dma3chan0-copy0: summary 400000 tests, 0 failures iops: 61524 KB/s 246098 (0)
The details of a data miscompare error are also emitted, but do not follow the
above format.
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