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
63.. hint::
64  available channel list could be extracted by running the following command::
65
66    % ls -1 /sys/class/dma/
67
68Once started a message like " dmatest: Added 1 threads using dma0chan0" is
69emitted. A thread for that specific channel is created and is now pending, the
70pending thread is started once run is to 1.
71
72Note that running a new test will not stop any in progress test.
73
74The following command returns the state of the test. ::
75
76    % cat /sys/module/dmatest/parameters/run
77
78To wait for test completion userpace can poll 'run' until it is false, or use
79the wait parameter. Specifying 'wait=1' when loading the module causes module
80initialization to pause until a test run has completed, while reading
81/sys/module/dmatest/parameters/wait waits for any running test to complete
82before returning. For example, the following scripts wait for 42 tests
83to complete before exiting. Note that if 'iterations' is set to 'infinite' then
84waiting is disabled.
85
86Example::
87
88    % modprobe dmatest run=1 iterations=42 wait=1
89    % modprobe -r dmatest
90
91...or::
92
93    % modprobe dmatest run=1 iterations=42
94    % cat /sys/module/dmatest/parameters/wait
95    % modprobe -r dmatest
96
97Part 3 - When built-in in the kernel
98====================================
99
100The module parameters that is supplied to the kernel command line will be used
101for the first performed test. After user gets a control, the test could be
102re-run with the same or different parameters. For the details see the above
103section `Part 2 - When dmatest is built as a module`_.
104
105In both cases the module parameters are used as the actual values for the test
106case. You always could check them at run-time by running ::
107
108    % grep -H . /sys/module/dmatest/parameters/*
109
110Part 4 - Gathering the test results
111===================================
112
113Test results are printed to the kernel log buffer with the format::
114
115    "dmatest: result <channel>: <test id>: '<error msg>' with src_off=<val> dst_off=<val> len=<val> (<err code>)"
116
117Example of output::
118
119    % dmesg | tail -n 1
120    dmatest: result dma0chan0-copy0: #1: No errors with src_off=0x7bf dst_off=0x8ad len=0x3fea (0)
121
122The message format is unified across the different types of errors. A
123number in the parentheses represents additional information, e.g. error
124code, error counter, or status. A test thread also emits a summary line at
125completion listing the number of tests executed, number that failed, and a
126result code.
127
128Example::
129
130    % dmesg | tail -n 1
131    dmatest: dma0chan0-copy0: summary 1 test, 0 failures 1000 iops 100000 KB/s (0)
132
133The details of a data miscompare error are also emitted, but do not follow the
134above format.
135
136Part 5 - Handling channel allocation
137====================================
138
139Allocating Channels
140-------------------
141
142Channels are required to be configured prior to starting the test run.
143Attempting to run the test without configuring the channels will fail.
144
145Example::
146
147    % echo 1 > /sys/module/dmatest/parameters/run
148    dmatest: Could not start test, no channels configured
149
150Channels are registered using the "channel" parameter. Channels can be requested by their
151name, once requested, the channel is registered and a pending thread is added to the test list.
152
153Example::
154
155    % echo dma0chan2 > /sys/module/dmatest/parameters/channel
156    dmatest: Added 1 threads using dma0chan2
157
158More channels can be added by repeating the example above.
159Reading back the channel parameter will return the name of last channel that was added successfully.
160
161Example::
162
163    % echo dma0chan1 > /sys/module/dmatest/parameters/channel
164    dmatest: Added 1 threads using dma0chan1
165    % echo dma0chan2 > /sys/module/dmatest/parameters/channel
166    dmatest: Added 1 threads using dma0chan2
167    % cat /sys/module/dmatest/parameters/channel
168    dma0chan2
169
170Another method of requesting channels is to request a channel with an empty string, Doing so
171will request all channels available to be tested:
172
173Example::
174
175    % echo "" > /sys/module/dmatest/parameters/channel
176    dmatest: Added 1 threads using dma0chan0
177    dmatest: Added 1 threads using dma0chan3
178    dmatest: Added 1 threads using dma0chan4
179    dmatest: Added 1 threads using dma0chan5
180    dmatest: Added 1 threads using dma0chan6
181    dmatest: Added 1 threads using dma0chan7
182    dmatest: Added 1 threads using dma0chan8
183
184At any point during the test configuration, reading the "test_list" parameter will
185print the list of currently pending tests.
186
187Example::
188
189    % cat /sys/module/dmatest/parameters/test_list
190    dmatest: 1 threads using dma0chan0
191    dmatest: 1 threads using dma0chan3
192    dmatest: 1 threads using dma0chan4
193    dmatest: 1 threads using dma0chan5
194    dmatest: 1 threads using dma0chan6
195    dmatest: 1 threads using dma0chan7
196    dmatest: 1 threads using dma0chan8
197
198Note: Channels will have to be configured for each test run as channel configurations do not
199carry across to the next test run.
200
201Releasing Channels
202-------------------
203
204Channels can be freed by setting run to 0.
205
206Example::
207    % echo dma0chan1 > /sys/module/dmatest/parameters/channel
208    dmatest: Added 1 threads using dma0chan1
209    % cat /sys/class/dma/dma0chan1/in_use
210    1
211    % echo 0 > /sys/module/dmatest/parameters/run
212    % cat /sys/class/dma/dma0chan1/in_use
213    0
214
215Channels allocated by previous test runs are automatically freed when a new
216channel is requested after completing a successful test run.
217