233 lines
8.3 KiB
ReStructuredText
233 lines
8.3 KiB
ReStructuredText
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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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The dmatest module tests DMA memcpy, memset, XOR and RAID6 P+Q operations using
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various lengths and various offsets into the source and destination buffers. It
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will initialize both buffers with a repeatable pattern and verify that the DMA
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engine copies the requested region and nothing more. It will also verify that
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the bytes aren't swapped around, and that the source buffer isn't modified.
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The dmatest module can be configured to test a specific channel. It can also
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test multiple channels at the same time, and it can start multiple threads
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competing for the same channel.
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.. note::
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The test suite works only on the channels that have at least one
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capability of the following: DMA_MEMCPY (memory-to-memory), DMA_MEMSET
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(const-to-memory or memory-to-memory, when emulated), DMA_XOR, DMA_PQ.
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.. note::
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In case of any related questions use the official mailing list
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dmaengine@vger.kernel.org.
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Part 1 - How to build the test module
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=====================================
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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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==========================================
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Example of usage::
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% modprobe dmatest timeout=2000 iterations=1 channel=dma0chan0 run=1
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...or::
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% modprobe dmatest
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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 dma0chan0 > /sys/module/dmatest/parameters/channel
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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.timeout=2000 dmatest.iterations=1 dmatest.channel=dma0chan0 dmatest.run=1
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Example of multi-channel test usage (new in the 5.0 kernel)::
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% modprobe dmatest
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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 dma0chan0 > /sys/module/dmatest/parameters/channel
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% echo dma0chan1 > /sys/module/dmatest/parameters/channel
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% echo dma0chan2 > /sys/module/dmatest/parameters/channel
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% echo 1 > /sys/module/dmatest/parameters/run
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.. note::
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For all tests, starting in the 5.0 kernel, either single- or multi-channel,
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the channel parameter(s) must be set after all other parameters. It is at
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that time that the existing parameter values are acquired for use by the
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thread(s). All other parameters are shared. Therefore, if changes are made
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to any of the other parameters, and an additional channel specified, the
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(shared) parameters used for all threads will use the new values.
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After the channels are specified, each thread is set as pending. All threads
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begin execution when the run parameter is set to 1.
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.. hint::
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A list of available channels can be found by running the following command::
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% ls -1 /sys/class/dma/
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Once started a message like " dmatest: Added 1 threads using dma0chan0" is
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emitted. A thread for that specific channel is created and is now pending, the
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pending thread is started once run is to 1.
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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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====================================
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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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===================================
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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
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number in the parentheses represents additional information, e.g. error
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code, error counter, or status. A test thread also emits a summary line at
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completion listing the number of tests executed, number that failed, and a
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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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Part 5 - Handling channel allocation
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====================================
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Allocating Channels
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-------------------
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Channels do not need to be configured prior to starting a test run. Attempting
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to run the test without configuring the channels will result in testing any
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channels that are available.
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Example::
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% echo 1 > /sys/module/dmatest/parameters/run
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dmatest: No channels configured, continue with any
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Channels are registered using the "channel" parameter. Channels can be requested by their
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name, once requested, the channel is registered and a pending thread is added to the test list.
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Example::
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% echo dma0chan2 > /sys/module/dmatest/parameters/channel
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dmatest: Added 1 threads using dma0chan2
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More channels can be added by repeating the example above.
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Reading back the channel parameter will return the name of last channel that was added successfully.
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Example::
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% echo dma0chan1 > /sys/module/dmatest/parameters/channel
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dmatest: Added 1 threads using dma0chan1
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% echo dma0chan2 > /sys/module/dmatest/parameters/channel
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dmatest: Added 1 threads using dma0chan2
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% cat /sys/module/dmatest/parameters/channel
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dma0chan2
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Another method of requesting channels is to request a channel with an empty string, Doing so
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will request all channels available to be tested:
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Example::
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% echo "" > /sys/module/dmatest/parameters/channel
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dmatest: Added 1 threads using dma0chan0
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dmatest: Added 1 threads using dma0chan3
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dmatest: Added 1 threads using dma0chan4
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dmatest: Added 1 threads using dma0chan5
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dmatest: Added 1 threads using dma0chan6
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dmatest: Added 1 threads using dma0chan7
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dmatest: Added 1 threads using dma0chan8
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At any point during the test configuration, reading the "test_list" parameter will
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print the list of currently pending tests.
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Example::
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% cat /sys/module/dmatest/parameters/test_list
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dmatest: 1 threads using dma0chan0
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dmatest: 1 threads using dma0chan3
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dmatest: 1 threads using dma0chan4
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dmatest: 1 threads using dma0chan5
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dmatest: 1 threads using dma0chan6
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dmatest: 1 threads using dma0chan7
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dmatest: 1 threads using dma0chan8
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Note: Channels will have to be configured for each test run as channel configurations do not
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carry across to the next test run.
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Releasing Channels
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-------------------
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Channels can be freed by setting run to 0.
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Example::
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% echo dma0chan1 > /sys/module/dmatest/parameters/channel
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dmatest: Added 1 threads using dma0chan1
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% cat /sys/class/dma/dma0chan1/in_use
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1
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% echo 0 > /sys/module/dmatest/parameters/run
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% cat /sys/class/dma/dma0chan1/in_use
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0
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Channels allocated by previous test runs are automatically freed when a new
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channel is requested after completing a successful test run.
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