1 DMA Test Guide 2 ============== 3 4 Andy Shevchenko <andriy.shevchenko@linux.intel.com> 5 6This small document introduces how to test DMA drivers using dmatest module. 7 8 Part 1 - How to build the test module 9 10The menuconfig contains an option that could be found by following path: 11 Device Drivers -> DMA Engine support -> DMA Test client 12 13In the configuration file the option called CONFIG_DMATEST. The dmatest could 14be built as module or inside kernel. Let's consider those cases. 15 16 Part 2 - When dmatest is built as a module... 17 18After mounting debugfs and loading the module, the /sys/kernel/debug/dmatest 19folder with nodes will be created. They are the same as module parameters with 20addition of the 'run' node that controls run and stop phases of the test. 21 22Note that in this case test will not run on load automatically. 23 24Example of usage: 25 % echo dma0chan0 > /sys/kernel/debug/dmatest/channel 26 % echo 2000 > /sys/kernel/debug/dmatest/timeout 27 % echo 1 > /sys/kernel/debug/dmatest/iterations 28 % echo 1 > /sys/kernel/debug/dmatest/run 29 30Hint: available channel list could be extracted by running the following 31command: 32 % ls -1 /sys/class/dma/ 33 34After a while you will start to get messages about current status or error like 35in the original code. 36 37Note that running a new test will not stop any in progress test. 38 39The following command should return actual state of the test. 40 % cat /sys/kernel/debug/dmatest/run 41 42To wait for test done the user may perform a busy loop that checks the state. 43 44 % while [ $(cat /sys/kernel/debug/dmatest/run) = "Y" ] 45 > do 46 > echo -n "." 47 > sleep 1 48 > done 49 > echo 50 51 Part 3 - When built-in in the kernel... 52 53The module parameters that is supplied to the kernel command line will be used 54for the first performed test. After user gets a control, the test could be 55re-run with the same or different parameters. For the details see the above 56section "Part 2 - When dmatest is built as a module..." 57 58In both cases the module parameters are used as initial values for the test case. 59You always could check them at run-time by running 60 % grep -H . /sys/module/dmatest/parameters/* 61 62 Part 4 - Gathering the test results 63 64The module provides a storage for the test results in the memory. The gathered 65data could be used after test is done. 66 67The special file 'results' in the debugfs represents gathered data of the in 68progress test. The messages collected are printed to the kernel log as well. 69 70Example of output: 71 % cat /sys/kernel/debug/dmatest/results 72 dma0chan0-copy0: #1: No errors with src_off=0x7bf dst_off=0x8ad len=0x3fea (0) 73 74The message format is unified across the different types of errors. A number in 75the parens represents additional information, e.g. error code, error counter, 76or status. 77 78Comparison between buffers is stored to the dedicated structure. 79 80Note that the verify result is now accessible only via file 'results' in the 81debugfs. 82