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diff --git a/Documentation/driver-api/dmaengine/dmatest.rst b/Documentation/driver-api/dmaengine/dmatest.rst new file mode 100644 index 000000000..cf9859cd0 --- /dev/null +++ b/Documentation/driver-api/dmaengine/dmatest.rst @@ -0,0 +1,232 @@ +============== +DMA Test Guide +============== + +Andy Shevchenko <andriy.shevchenko@linux.intel.com> + +This small document introduces how to test DMA drivers using dmatest module. + +The dmatest module tests DMA memcpy, memset, XOR and RAID6 P+Q operations using +various lengths and various offsets into the source and destination buffers. It +will initialize both buffers with a repeatable pattern and verify that the DMA +engine copies the requested region and nothing more. It will also verify that +the bytes aren't swapped around, and that the source buffer isn't modified. + +The dmatest module can be configured to test a specific channel. It can also +test multiple channels at the same time, and it can start multiple threads +competing for the same channel. + +.. note:: + The test suite works only on the channels that have at least one + capability of the following: DMA_MEMCPY (memory-to-memory), DMA_MEMSET + (const-to-memory or memory-to-memory, when emulated), DMA_XOR, DMA_PQ. + +.. note:: + In case of any related questions use the official mailing list + dmaengine@vger.kernel.org. + +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 timeout=2000 iterations=1 channel=dma0chan0 run=1 + +...or:: + + % modprobe dmatest + % echo 2000 > /sys/module/dmatest/parameters/timeout + % echo 1 > /sys/module/dmatest/parameters/iterations + % echo dma0chan0 > /sys/module/dmatest/parameters/channel + % echo 1 > /sys/module/dmatest/parameters/run + +...or on the kernel command line:: + + dmatest.timeout=2000 dmatest.iterations=1 dmatest.channel=dma0chan0 dmatest.run=1 + +Example of multi-channel test usage (new in the 5.0 kernel):: + + % modprobe dmatest + % echo 2000 > /sys/module/dmatest/parameters/timeout + % echo 1 > /sys/module/dmatest/parameters/iterations + % echo dma0chan0 > /sys/module/dmatest/parameters/channel + % echo dma0chan1 > /sys/module/dmatest/parameters/channel + % echo dma0chan2 > /sys/module/dmatest/parameters/channel + % echo 1 > /sys/module/dmatest/parameters/run + +.. note:: + For all tests, starting in the 5.0 kernel, either single- or multi-channel, + the channel parameter(s) must be set after all other parameters. It is at + that time that the existing parameter values are acquired for use by the + thread(s). All other parameters are shared. Therefore, if changes are made + to any of the other parameters, and an additional channel specified, the + (shared) parameters used for all threads will use the new values. + After the channels are specified, each thread is set as pending. All threads + begin execution when the run parameter is set to 1. + +.. hint:: + A list of available channels can be found by running the following command:: + + % ls -1 /sys/class/dma/ + +Once started a message like " dmatest: Added 1 threads using dma0chan0" is +emitted. A thread for that specific channel is created and is now pending, the +pending thread is started once run is to 1. + +Note that running a new test will not stop any in progress test. + +The following command returns the state of the test. :: + + % cat /sys/module/dmatest/parameters/run + +To wait for test completion userpace can poll 'run' until it is false, or use +the wait parameter. Specifying 'wait=1' when loading the module causes module +initialization to pause until a test run has completed, while reading +/sys/module/dmatest/parameters/wait waits for any running test to complete +before returning. For example, the following scripts wait for 42 tests +to complete before exiting. Note that if 'iterations' is set to 'infinite' then +waiting is disabled. + +Example:: + + % modprobe dmatest run=1 iterations=42 wait=1 + % modprobe -r dmatest + +...or:: + + % modprobe dmatest run=1 iterations=42 + % cat /sys/module/dmatest/parameters/wait + % modprobe -r dmatest + +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 parentheses 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: dma0chan0-copy0: summary 1 test, 0 failures 1000 iops 100000 KB/s (0) + +The details of a data miscompare error are also emitted, but do not follow the +above format. + +Part 5 - Handling channel allocation +==================================== + +Allocating Channels +------------------- + +Channels do not need to be configured prior to starting a test run. Attempting +to run the test without configuring the channels will result in testing any +channels that are available. + +Example:: + + % echo 1 > /sys/module/dmatest/parameters/run + dmatest: No channels configured, continue with any + +Channels are registered using the "channel" parameter. Channels can be requested by their +name, once requested, the channel is registered and a pending thread is added to the test list. + +Example:: + + % echo dma0chan2 > /sys/module/dmatest/parameters/channel + dmatest: Added 1 threads using dma0chan2 + +More channels can be added by repeating the example above. +Reading back the channel parameter will return the name of last channel that was added successfully. + +Example:: + + % echo dma0chan1 > /sys/module/dmatest/parameters/channel + dmatest: Added 1 threads using dma0chan1 + % echo dma0chan2 > /sys/module/dmatest/parameters/channel + dmatest: Added 1 threads using dma0chan2 + % cat /sys/module/dmatest/parameters/channel + dma0chan2 + +Another method of requesting channels is to request a channel with an empty string, Doing so +will request all channels available to be tested: + +Example:: + + % echo "" > /sys/module/dmatest/parameters/channel + dmatest: Added 1 threads using dma0chan0 + dmatest: Added 1 threads using dma0chan3 + dmatest: Added 1 threads using dma0chan4 + dmatest: Added 1 threads using dma0chan5 + dmatest: Added 1 threads using dma0chan6 + dmatest: Added 1 threads using dma0chan7 + dmatest: Added 1 threads using dma0chan8 + +At any point during the test configuration, reading the "test_list" parameter will +print the list of currently pending tests. + +Example:: + + % cat /sys/module/dmatest/parameters/test_list + dmatest: 1 threads using dma0chan0 + dmatest: 1 threads using dma0chan3 + dmatest: 1 threads using dma0chan4 + dmatest: 1 threads using dma0chan5 + dmatest: 1 threads using dma0chan6 + dmatest: 1 threads using dma0chan7 + dmatest: 1 threads using dma0chan8 + +Note: Channels will have to be configured for each test run as channel configurations do not +carry across to the next test run. + +Releasing Channels +------------------- + +Channels can be freed by setting run to 0. + +Example:: + + % echo dma0chan1 > /sys/module/dmatest/parameters/channel + dmatest: Added 1 threads using dma0chan1 + % cat /sys/class/dma/dma0chan1/in_use + 1 + % echo 0 > /sys/module/dmatest/parameters/run + % cat /sys/class/dma/dma0chan1/in_use + 0 + +Channels allocated by previous test runs are automatically freed when a new +channel is requested after completing a successful test run. |