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https://github.com/torvalds/linux
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92 lines
3.4 KiB
Text
92 lines
3.4 KiB
Text
DMA Test Guide
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==============
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Andy Shevchenko <andriy.shevchenko@linux.intel.com>
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This small document introduces how to test DMA drivers using dmatest module.
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Part 1 - How to build the test module
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The menuconfig contains an option that could be found by following path:
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Device Drivers -> DMA Engine support -> DMA Test client
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In the configuration file the option called CONFIG_DMATEST. The dmatest could
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be built as module or inside kernel. Let's consider those cases.
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Part 2 - When dmatest is built as a module...
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Example of usage:
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% modprobe dmatest channel=dma0chan0 timeout=2000 iterations=1 run=1
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...or:
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% modprobe dmatest
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% echo dma0chan0 > /sys/module/dmatest/parameters/channel
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% echo 2000 > /sys/module/dmatest/parameters/timeout
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% echo 1 > /sys/module/dmatest/parameters/iterations
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% echo 1 > /sys/module/dmatest/parameters/run
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...or on the kernel command line:
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dmatest.channel=dma0chan0 dmatest.timeout=2000 dmatest.iterations=1 dmatest.run=1
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Hint: available channel list could be extracted by running the following
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command:
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% ls -1 /sys/class/dma/
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Once started a message like "dmatest: Started 1 threads using dma0chan0" is
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emitted. After that only test failure messages are reported until the test
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stops.
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Note that running a new test will not stop any in progress test.
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The following command returns the state of the test.
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% cat /sys/module/dmatest/parameters/run
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To wait for test completion userpace can poll 'run' until it is false, or use
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the wait parameter. Specifying 'wait=1' when loading the module causes module
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initialization to pause until a test run has completed, while reading
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/sys/module/dmatest/parameters/wait waits for any running test to complete
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before returning. For example, the following scripts wait for 42 tests
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to complete before exiting. Note that if 'iterations' is set to 'infinite' then
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waiting is disabled.
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Example:
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% modprobe dmatest run=1 iterations=42 wait=1
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% modprobe -r dmatest
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...or:
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% modprobe dmatest run=1 iterations=42
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% cat /sys/module/dmatest/parameters/wait
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% modprobe -r dmatest
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Part 3 - When built-in in the kernel...
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The module parameters that is supplied to the kernel command line will be used
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for the first performed test. After user gets a control, the test could be
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re-run with the same or different parameters. For the details see the above
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section "Part 2 - When dmatest is built as a module..."
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In both cases the module parameters are used as the actual values for the test
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case. You always could check them at run-time by running
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% grep -H . /sys/module/dmatest/parameters/*
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Part 4 - Gathering the test results
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Test results are printed to the kernel log buffer with the format:
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"dmatest: result <channel>: <test id>: '<error msg>' with src_off=<val> dst_off=<val> len=<val> (<err code>)"
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Example of output:
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% dmesg | tail -n 1
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dmatest: result dma0chan0-copy0: #1: No errors with src_off=0x7bf dst_off=0x8ad len=0x3fea (0)
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The message format is unified across the different types of errors. A number in
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the parens represents additional information, e.g. error code, error counter,
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or status. A test thread also emits a summary line at completion listing the
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number of tests executed, number that failed, and a result code.
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Example:
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% dmesg | tail -n 1
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dmatest: dma0chan0-copy0: summary 1 test, 0 failures 1000 iops 100000 KB/s (0)
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The details of a data miscompare error are also emitted, but do not follow the
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above format.
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