82 lines
2.8 KiB
Plaintext
82 lines
2.8 KiB
Plaintext
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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After mounting debugfs and loading the module, the /sys/kernel/debug/dmatest
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folder with nodes will be created. They are the same as module parameters with
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addition of the 'run' node that controls run and stop phases of the test.
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Note that in this case test will not run on load automatically.
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Example of usage:
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% echo dma0chan0 > /sys/kernel/debug/dmatest/channel
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% echo 2000 > /sys/kernel/debug/dmatest/timeout
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% echo 1 > /sys/kernel/debug/dmatest/iterations
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% echo 1 > /sys/kernel/debug/dmatest/run
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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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After a while you will start to get messages about current status or error like
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in the original code.
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Note that running a new test will stop any in progress test.
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The following command should return actual state of the test.
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% cat /sys/kernel/debug/dmatest/run
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To wait for test done the user may perform a busy loop that checks the state.
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% while [ $(cat /sys/kernel/debug/dmatest/run) = "Y" ]
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> do
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> echo -n "."
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> sleep 1
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> done
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> echo
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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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interrupted or re-run with same or different parameters. For the details see
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the above section "Part 2 - When dmatest is built as a module..."
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In both cases the module parameters are used as initial values for the test case.
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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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The module provides a storage for the test results in the memory. The gathered
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data could be used after test is done.
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The special file 'results' in the debugfs represents gathered data of the in
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progress test. The messages collected are printed to the kernel log as well.
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Example of output:
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% cat /sys/kernel/debug/dmatest/results
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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.
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Comparison between buffers is stored to the dedicated structure.
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Note that the verify result is now accessible only via file 'results' in the
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debugfs.
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