[V2,5/5] dmaengine: Documentation: Add documentation for multi chan testing

[Peter Ujfalusi <peter.ujfalusi@ti.com>]

Hi,

On 2018-08-31 14:03, Seraj Alijan wrote:
> Modify documentation to add multi channel testing support.
> 
> Signed-off-by: Seraj Alijan <seraj.alijan@sondrel.com>
> ---
>  Documentation/driver-api/dmaengine/dmatest.rst | 27 ++++++++++++++++++++------
>  1 file changed, 21 insertions(+), 6 deletions(-)
> 
> diff --git a/Documentation/driver-api/dmaengine/dmatest.rst b/Documentation/driver-api/dmaengine/dmatest.rst
> index 7ce5e71..0a7e4c3 100644
> --- a/Documentation/driver-api/dmaengine/dmatest.rst
> +++ b/Documentation/driver-api/dmaengine/dmatest.rst
> @@ -26,28 +26,43 @@ Part 2 - When dmatest is built as a module
>  
>  Example of usage::
>  
> -    % modprobe dmatest channel=dma0chan0 timeout=2000 iterations=1 run=1
> +    % modprobe dmatest timeout=2000 iterations=1 channel=dma0chan0 run=1
>  
>  ...or::
>  
>      % modprobe dmatest
> -    % echo dma0chan0 > /sys/module/dmatest/parameters/channel
>      % 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.channel=dma0chan0 dmatest.timeout=2000 dmatest.iterations=1 dmatest.run=1
> +    dmatest.timeout=2000 dmatest.iterations=1 dmatest.channel=dma0chan0 dmatest.run=1
> +
> +Example of multi-channel test usage:
> +    % 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: 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.

When the channel is going to be released after this change?

It is a bit awkward currently that after the test finished the
channel(s) are still requested and it can be released by
cat /sys/module/dmatest/parameters/run

or to run the test again and before the next run the channel(s) are
going to be released just to be requested again.

> 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.
>  .. hint::
>    available channel list could be extracted by running the following command::
>  
>      % ls -1 /sys/class/dma/
>  
> -Once started a message like "dmatest: Started 1 threads using dma0chan0" is
> -emitted. After that only test failure messages are reported until the test
> -stops.
> +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.
>  
> 

- Péter

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