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Diffstat (limited to 'kernel/Documentation/dmaengine/dmatest.txt')
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diff --git a/kernel/Documentation/dmaengine/dmatest.txt b/kernel/Documentation/dmaengine/dmatest.txt new file mode 100644 index 000000000..dd77a81bd --- /dev/null +++ b/kernel/Documentation/dmaengine/dmatest.txt @@ -0,0 +1,92 @@ + 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 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 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: 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. |