Adding upstream version 6.6.15.upstream/6.6.15

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

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+==============
+DMA Test Guide
+==============
+
+Andy Shevchenko <andriy.shevchenko@linux.intel.com>
+
+This small document introduces how to test DMA drivers using dmatest module.
+
+The dmatest module tests DMA memcpy, memset, XOR and RAID6 P+Q operations using
+various lengths and various offsets into the source and destination buffers. It
+will initialize both buffers with a repeatable pattern and verify that the DMA
+engine copies the requested region and nothing more. It will also verify that
+the bytes aren't swapped around, and that the source buffer isn't modified.
+
+The dmatest module can be configured to test a specific channel. It can also
+test multiple channels at the same time, and it can start multiple threads
+competing for the same channel.
+
+.. note::
+  The test suite works only on the channels that have at least one
+  capability of the following: DMA_MEMCPY (memory-to-memory), DMA_MEMSET
+  (const-to-memory or memory-to-memory, when emulated), DMA_XOR, DMA_PQ.
+
+.. note::
+  In case of any related questions use the official mailing list
+  dmaengine@vger.kernel.org.
+
+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
+==========================================
+
+Example of usage::
+
+    % modprobe dmatest timeout=2000 iterations=1 channel=dma0chan0 run=1
+
+...or::
+
+    % modprobe dmatest
+    % echo 2000 > /sys/module/dmatest/parameters/timeout
+    % echo 1 > /sys/module/dmatest/parameters/iterations
+    % echo dma0chan0 > /sys/module/dmatest/parameters/channel
+    % echo 1 > /sys/module/dmatest/parameters/run
+
+...or on the kernel command line::
+
+    dmatest.timeout=2000 dmatest.iterations=1 dmatest.channel=dma0chan0 dmatest.run=1
+
+Example of multi-channel test usage (new in the 5.0 kernel)::
+
+    % modprobe dmatest
+    % echo 2000 > /sys/module/dmatest/parameters/timeout
+    % echo 1 > /sys/module/dmatest/parameters/iterations
+    % echo dma0chan0 > /sys/module/dmatest/parameters/channel
+    % echo dma0chan1 > /sys/module/dmatest/parameters/channel
+    % echo dma0chan2 > /sys/module/dmatest/parameters/channel
+    % echo 1 > /sys/module/dmatest/parameters/run
+
+.. note::
+  For all tests, starting in the 5.0 kernel, either single- or multi-channel,
+  the channel parameter(s) must be set after all other parameters. It is at
+  that time that the existing parameter values are acquired for use by the
+  thread(s). All other parameters are shared. Therefore, if changes are made
+  to any of the other parameters, and an additional channel specified, the
+  (shared) parameters used for all threads will use the new values.
+  After the channels are specified, each thread is set as pending. All threads
+  begin execution when the run parameter is set to 1.
+
+.. hint::
+  A list of available channels can be found by running the following command::
+
+    % ls -1 /sys/class/dma/
+
+Once started a message like " dmatest: Added 1 threads using dma0chan0" is
+emitted. A thread for that specific channel is created and is now pending, the
+pending thread is started once run is to 1.
+
+Note that running a new test will not stop any in progress test.
+
+The following command returns the state of the test. ::
+
+    % cat /sys/module/dmatest/parameters/run
+
+To wait for test completion userspace can poll 'run' until it is false, or use
+the wait parameter. Specifying 'wait=1' when loading the module causes module
+initialization to pause until a test run has completed, while reading
+/sys/module/dmatest/parameters/wait waits for any running test to complete
+before returning. For example, the following scripts wait for 42 tests
+to complete before exiting. Note that if 'iterations' is set to 'infinite' then
+waiting is disabled.
+
+Example::
+
+    % modprobe dmatest run=1 iterations=42 wait=1
+    % modprobe -r dmatest
+
+...or::
+
+    % modprobe dmatest run=1 iterations=42
+    % cat /sys/module/dmatest/parameters/wait
+    % modprobe -r dmatest
+
+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
+re-run with the 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 the actual values for the test
+case. You always could check them at run-time by running ::
+
+    % grep -H . /sys/module/dmatest/parameters/*
+
+Part 4 - Gathering the test results
+===================================
+
+Test results are printed to the kernel log buffer with the format::
+
+    "dmatest: result <channel>: <test id>: '<error msg>' with src_off=<val> dst_off=<val> len=<val> (<err code>)"
+
+Example of output::
+
+    % dmesg | tail -n 1
+    dmatest: result dma0chan0-copy0: #1: No errors with src_off=0x7bf dst_off=0x8ad len=0x3fea (0)
+
+The message format is unified across the different types of errors. A
+number in the parentheses represents additional information, e.g. error
+code, error counter, or status. A test thread also emits a summary line at
+completion listing the number of tests executed, number that failed, and a
+result code.
+
+Example::
+
+    % dmesg | tail -n 1
+    dmatest: dma0chan0-copy0: summary 1 test, 0 failures 1000 iops 100000 KB/s (0)
+
+The details of a data miscompare error are also emitted, but do not follow the
+above format.
+
+Part 5 - Handling channel allocation
+====================================
+
+Allocating Channels
+-------------------
+
+Channels do not need to be configured prior to starting a test run. Attempting
+to run the test without configuring the channels will result in testing any
+channels that are available.
+
+Example::
+
+    % echo 1 > /sys/module/dmatest/parameters/run
+    dmatest: No channels configured, continue with any
+
+Channels are registered using the "channel" parameter. Channels can be requested by their
+name, once requested, the channel is registered and a pending thread is added to the test list.
+
+Example::
+
+    % echo dma0chan2 > /sys/module/dmatest/parameters/channel
+    dmatest: Added 1 threads using dma0chan2
+
+More channels can be added by repeating the example above.
+Reading back the channel parameter will return the name of last channel that was added successfully.
+
+Example::
+
+    % echo dma0chan1 > /sys/module/dmatest/parameters/channel
+    dmatest: Added 1 threads using dma0chan1
+    % echo dma0chan2 > /sys/module/dmatest/parameters/channel
+    dmatest: Added 1 threads using dma0chan2
+    % cat /sys/module/dmatest/parameters/channel
+    dma0chan2
+
+Another method of requesting channels is to request a channel with an empty string, Doing so
+will request all channels available to be tested:
+
+Example::
+
+    % echo "" > /sys/module/dmatest/parameters/channel
+    dmatest: Added 1 threads using dma0chan0
+    dmatest: Added 1 threads using dma0chan3
+    dmatest: Added 1 threads using dma0chan4
+    dmatest: Added 1 threads using dma0chan5
+    dmatest: Added 1 threads using dma0chan6
+    dmatest: Added 1 threads using dma0chan7
+    dmatest: Added 1 threads using dma0chan8
+
+At any point during the test configuration, reading the "test_list" parameter will
+print the list of currently pending tests.
+
+Example::
+
+    % cat /sys/module/dmatest/parameters/test_list
+    dmatest: 1 threads using dma0chan0
+    dmatest: 1 threads using dma0chan3
+    dmatest: 1 threads using dma0chan4
+    dmatest: 1 threads using dma0chan5
+    dmatest: 1 threads using dma0chan6
+    dmatest: 1 threads using dma0chan7
+    dmatest: 1 threads using dma0chan8
+
+Note: Channels will have to be configured for each test run as channel configurations do not
+carry across to the next test run.
+
+Releasing Channels
+-------------------
+
+Channels can be freed by setting run to 0.
+
+Example::
+
+    % echo dma0chan1 > /sys/module/dmatest/parameters/channel
+    dmatest: Added 1 threads using dma0chan1
+    % cat /sys/class/dma/dma0chan1/in_use
+    1
+    % echo 0 > /sys/module/dmatest/parameters/run
+    % cat /sys/class/dma/dma0chan1/in_use
+    0
+
+Channels allocated by previous test runs are automatically freed when a new
+channel is requested after completing a successful test run.