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diff --git a/Documentation/dmatest.txt b/Documentation/dmatest.txt new file mode 100644 index 000000000000..9a90729bdee6 --- /dev/null +++ b/Documentation/dmatest.txt @@ -0,0 +1,48 @@ + 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... + +After mounting debugfs and loading the module, the /sys/kernel/debug/dmatest +folder with nodes will be created. They are the same as module parameters with +addition of the 'run' node that controls run and stop phases of the test. + +Note that in this case test will not run on load automatically. + +Example of usage: + % echo dma0chan0 > /sys/kernel/debug/dmatest/channel + % echo 2000 > /sys/kernel/debug/dmatest/timeout + % echo 1 > /sys/kernel/debug/dmatest/iterations + % echo 1 > /sys/kernel/debug/dmatest/run + +Hint: available channel list could be extracted by running the following +command: + % ls -1 /sys/class/dma/ + +After a while you will start to get messages about current status or error like +in the original code. + +Note that running a new test will stop any in progress test. + + 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 +interrupted or re-run with 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 initial values for the test case. +You always could check them at run-time by running + % grep -H . /sys/module/dmatest/parameters/* |