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The recommended HDA HW programming sequence for setting the DMA format requires that the link DMA and host DMA channels be coupled before setting the format. This change means that host DMA or link DMA channels be reserved even if only one is used. Statically assigned link DMA channels would mean that all the corresponding host DMA channels will need to be reserved, leaving only a few channels available at run-time. So, the suggestion here is to switch to dynamically assigning both host DMA channels and link DMA channels are run-time. The host DMA channel is assigned when the pcm is opened as before. While choosing the link DMA channel, if the host DMA channel corresponding to the link DMA channel is already taken, the proposed method checks to make sure that the BE is connected to the FE that has been assigned this host DMA channel. Once the link DMA channel is assigned, an IPC is sent to the DSP to set the link DMA channel. The link DMA channel is freed during hw_free() and also in the SUSPEND trigger callback. It will be re-assigned when hw_params are set upon resume. Signed-off-by: Ranjani Sridharan <ranjani.sridharan@linux.intel.com> Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com> Signed-off-by: Mark Brown <broonie@kernel.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.