Based on kernel version 3.12. Page generated on 2013-11-13 21:57 EST.
1 DMA Test Guide 2 ============== 3 4 Andy Shevchenko <email@example.com> 5 6 This small document introduces how to test DMA drivers using dmatest module. 7 8 Part 1 - How to build the test module 9 10 The menuconfig contains an option that could be found by following path: 11 Device Drivers -> DMA Engine support -> DMA Test client 12 13 In the configuration file the option called CONFIG_DMATEST. The dmatest could 14 be built as module or inside kernel. Let's consider those cases. 15 16 Part 2 - When dmatest is built as a module... 17 18 After mounting debugfs and loading the module, the /sys/kernel/debug/dmatest 19 folder with nodes will be created. There are two important files located. First 20 is the 'run' node that controls run and stop phases of the test, and the second 21 one, 'results', is used to get the test case results. 22 23 Note that in this case test will not run on load automatically. 24 25 Example of usage: 26 % echo dma0chan0 > /sys/module/dmatest/parameters/channel 27 % echo 2000 > /sys/module/dmatest/parameters/timeout 28 % echo 1 > /sys/module/dmatest/parameters/iterations 29 % echo 1 > /sys/kernel/debug/dmatest/run 30 31 Hint: available channel list could be extracted by running the following 32 command: 33 % ls -1 /sys/class/dma/ 34 35 After a while you will start to get messages about current status or error like 36 in the original code. 37 38 Note that running a new test will not stop any in progress test. 39 40 The following command should return actual state of the test. 41 % cat /sys/kernel/debug/dmatest/run 42 43 To wait for test done the user may perform a busy loop that checks the state. 44 45 % while [ $(cat /sys/kernel/debug/dmatest/run) = "Y" ] 46 > do 47 > echo -n "." 48 > sleep 1 49 > done 50 > echo 51 52 Part 3 - When built-in in the kernel... 53 54 The module parameters that is supplied to the kernel command line will be used 55 for the first performed test. After user gets a control, the test could be 56 re-run with the same or different parameters. For the details see the above 57 section "Part 2 - When dmatest is built as a module..." 58 59 In both cases the module parameters are used as the actual values for the test 60 case. You always could check them at run-time by running 61 % grep -H . /sys/module/dmatest/parameters/* 62 63 Part 4 - Gathering the test results 64 65 The module provides a storage for the test results in the memory. The gathered 66 data could be used after test is done. 67 68 The special file 'results' in the debugfs represents gathered data of the in 69 progress test. The messages collected are printed to the kernel log as well. 70 71 Example of output: 72 % cat /sys/kernel/debug/dmatest/results 73 dma0chan0-copy0: #1: No errors with src_off=0x7bf dst_off=0x8ad len=0x3fea (0) 74 75 The message format is unified across the different types of errors. A number in 76 the parens represents additional information, e.g. error code, error counter, 77 or status. 78 79 Comparison between buffers is stored to the dedicated structure. 80 81 Note that the verify result is now accessible only via file 'results' in the 82 debugfs.