1==============
2DMA Test Guide
3==============
4
5Andy Shevchenko <andriy.shevchenko@linux.intel.com>
6
7This small document introduces how to test DMA drivers using dmatest module.
8
9.. note::
10  The test suite works only on the channels that have at least one
11  capability of the following: DMA_MEMCPY (memory-to-memory), DMA_MEMSET
12  (const-to-memory or memory-to-memory, when emulated), DMA_XOR, DMA_PQ.
13
14.. note::
15  In case of any related questions use the official mailing list
16  dmaengine@vger.kernel.org.
17
18Part 1 - How to build the test module
19=====================================
20
21The menuconfig contains an option that could be found by following path:
22
23	Device Drivers -> DMA Engine support -> DMA Test client
24
25In the configuration file the option called CONFIG_DMATEST. The dmatest could
26be built as module or inside kernel. Let's consider those cases.
27
28Part 2 - When dmatest is built as a module
29==========================================
30
31Example of usage::
32
33    % modprobe dmatest timeout=2000 iterations=1 channel=dma0chan0 run=1
34
35...or::
36
37    % modprobe dmatest
38    % echo 2000 > /sys/module/dmatest/parameters/timeout
39    % echo 1 > /sys/module/dmatest/parameters/iterations
40    % echo dma0chan0 > /sys/module/dmatest/parameters/channel
41    % echo 1 > /sys/module/dmatest/parameters/run
42
43...or on the kernel command line::
44
45    dmatest.timeout=2000 dmatest.iterations=1 dmatest.channel=dma0chan0 dmatest.run=1
46
47Example of multi-channel test usage:
48    % modprobe dmatest
49    % echo 2000 > /sys/module/dmatest/parameters/timeout
50    % echo 1 > /sys/module/dmatest/parameters/iterations
51    % echo dma0chan0 > /sys/module/dmatest/parameters/channel
52    % echo dma0chan1 > /sys/module/dmatest/parameters/channel
53    % echo dma0chan2 > /sys/module/dmatest/parameters/channel
54    % echo 1 > /sys/module/dmatest/parameters/run
55
56Note: the channel parameter should always be the last parameter set prior to
57running the test (setting run=1), this is because upon setting the channel
58parameter, that specific channel is requested using the dmaengine and a thread
59is created with the existing parameters. This thread is set as pending
60and will be executed once run is set to 1. Any parameters set after the thread
61is created are not applied.
62.. hint::
63  available channel list could be extracted by running the following command::
64
65    % ls -1 /sys/class/dma/
66
67Once started a message like " dmatest: Added 1 threads using dma0chan0" is
68emitted. A thread for that specific channel is created and is now pending, the
69pending thread is started once run is to 1.
70
71Note that running a new test will not stop any in progress test.
72
73The following command returns the state of the test. ::
74
75    % cat /sys/module/dmatest/parameters/run
76
77To wait for test completion userpace can poll 'run' until it is false, or use
78the wait parameter. Specifying 'wait=1' when loading the module causes module
79initialization to pause until a test run has completed, while reading
80/sys/module/dmatest/parameters/wait waits for any running test to complete
81before returning. For example, the following scripts wait for 42 tests
82to complete before exiting. Note that if 'iterations' is set to 'infinite' then
83waiting is disabled.
84
85Example::
86
87    % modprobe dmatest run=1 iterations=42 wait=1
88    % modprobe -r dmatest
89
90...or::
91
92    % modprobe dmatest run=1 iterations=42
93    % cat /sys/module/dmatest/parameters/wait
94    % modprobe -r dmatest
95
96Part 3 - When built-in in the kernel
97====================================
98
99The module parameters that is supplied to the kernel command line will be used
100for the first performed test. After user gets a control, the test could be
101re-run with the same or different parameters. For the details see the above
102section `Part 2 - When dmatest is built as a module`_.
103
104In both cases the module parameters are used as the actual values for the test
105case. You always could check them at run-time by running ::
106
107    % grep -H . /sys/module/dmatest/parameters/*
108
109Part 4 - Gathering the test results
110===================================
111
112Test results are printed to the kernel log buffer with the format::
113
114    "dmatest: result <channel>: <test id>: '<error msg>' with src_off=<val> dst_off=<val> len=<val> (<err code>)"
115
116Example of output::
117
118    % dmesg | tail -n 1
119    dmatest: result dma0chan0-copy0: #1: No errors with src_off=0x7bf dst_off=0x8ad len=0x3fea (0)
120
121The message format is unified across the different types of errors. A
122number in the parentheses represents additional information, e.g. error
123code, error counter, or status. A test thread also emits a summary line at
124completion listing the number of tests executed, number that failed, and a
125result code.
126
127Example::
128
129    % dmesg | tail -n 1
130    dmatest: dma0chan0-copy0: summary 1 test, 0 failures 1000 iops 100000 KB/s (0)
131
132The details of a data miscompare error are also emitted, but do not follow the
133above format.
134
135Part 5 - Handling channel allocation
136====================================
137
138Allocating Channels
139-------------------
140
141Channels are required to be configured prior to starting the test run.
142Attempting to run the test without configuring the channels will fail.
143
144Example::
145
146    % echo 1 > /sys/module/dmatest/parameters/run
147    dmatest: Could not start test, no channels configured
148
149Channels are registered using the "channel" parameter. Channels can be requested by their
150name, once requested, the channel is registered and a pending thread is added to the test list.
151
152Example::
153
154    % echo dma0chan2 > /sys/module/dmatest/parameters/channel
155    dmatest: Added 1 threads using dma0chan2
156
157More channels can be added by repeating the example above.
158Reading back the channel parameter will return the name of last channel that was added successfully.
159
160Example::
161
162    % echo dma0chan1 > /sys/module/dmatest/parameters/channel
163    dmatest: Added 1 threads using dma0chan1
164    % echo dma0chan2 > /sys/module/dmatest/parameters/channel
165    dmatest: Added 1 threads using dma0chan2
166    % cat /sys/module/dmatest/parameters/channel
167    dma0chan2
168
169Another method of requesting channels is to request a channel with an empty string, Doing so
170will request all channels available to be tested:
171
172Example::
173
174    % echo "" > /sys/module/dmatest/parameters/channel
175    dmatest: Added 1 threads using dma0chan0
176    dmatest: Added 1 threads using dma0chan3
177    dmatest: Added 1 threads using dma0chan4
178    dmatest: Added 1 threads using dma0chan5
179    dmatest: Added 1 threads using dma0chan6
180    dmatest: Added 1 threads using dma0chan7
181    dmatest: Added 1 threads using dma0chan8
182
183At any point during the test configuration, reading the "test_list" parameter will
184print the list of currently pending tests.
185
186Example::
187
188    % cat /sys/module/dmatest/parameters/test_list
189    dmatest: 1 threads using dma0chan0
190    dmatest: 1 threads using dma0chan3
191    dmatest: 1 threads using dma0chan4
192    dmatest: 1 threads using dma0chan5
193    dmatest: 1 threads using dma0chan6
194    dmatest: 1 threads using dma0chan7
195    dmatest: 1 threads using dma0chan8
196
197Note: Channels will have to be configured for each test run as channel configurations do not
198carry across to the next test run.
199
200Releasing Channels
201-------------------
202
203Channels can be freed by setting run to 0.
204
205Example::
206    % echo dma0chan1 > /sys/module/dmatest/parameters/channel
207    dmatest: Added 1 threads using dma0chan1
208    % cat /sys/class/dma/dma0chan1/in_use
209    1
210    % echo 0 > /sys/module/dmatest/parameters/run
211    % cat /sys/class/dma/dma0chan1/in_use
212    0
213
214Channels allocated by previous test runs are automatically freed when a new
215channel is requested after completing a successful test run.
216