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Documentation: dmaengine: clean up description of dmatest usage

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Fix the formatting of the multi-channel test usage example. Call out
the note about parameter ordering and add detail on the settings of
parameters for the new version of dmatest.

Fixes: f80f9988a2 ("dmaengine: Documentation: Add documentation for multi chan testing")
Signed-off-by: Gary R Hook <gary.hook@amd.com>
Signed-off-by: Vinod Koul <vkoul@kernel.org>
This commit is contained in:
Hook, Gary 2019-06-24 18:35:01 +00:00 committed by Vinod Koul
parent 3145d73e69
commit 9dcb98a29b
1 changed files with 13 additions and 8 deletions
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21
Documentation/driver-api/dmaengine/dmatest.rst
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@ -44,7 +44,8 @@ Example of usage::
dmatest.timeout=2000 dmatest.iterations=1 dmatest.channel=dma0chan0 dmatest.run=1
Example of multi-channel test usage:
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
@ -53,15 +54,18 @@ Example of multi-channel test usage:
% echo dma0chan2 > /sys/module/dmatest/parameters/channel
% echo 1 > /sys/module/dmatest/parameters/run
Note: the channel parameter should always be the last parameter set prior to
running the test (setting run=1), this is because upon setting the channel
parameter, that specific channel is requested using the dmaengine and a thread
is created with the existing parameters. This thread is set as pending
and will be executed once run is set to 1. Any parameters set after the thread
is created are not applied.
.. 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::
available channel list could be extracted by running the following command::
A list of available channels can be found by running the following command::
% ls -1 /sys/class/dma/
@ -204,6 +208,7 @@ 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