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Currently if the source DMA device isn't ready to provide the channels capable of the SPI DMA transfers, the DW SSI controller will be registered with no DMA support. It isn't right since all what the driver needs to do is to postpone the probe procedure until the DMA device is ready. Let's fix that in the framework of the DWC SSI generic DMA implementation. First we need to use the dma_request_chan() method instead of the dma_request_slave_channel() function, because the later one is deprecated and most importantly doesn't return the failure cause but the NULL-pointer. Second we need to stop the DW SSI controller probe procedure if the -EPROBE_DEFER error is returned on the DMA initialization. The procedure will resume later when the channels are ready to be requested. Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru> Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com> Link: https://lore.kernel.org/r/20220624210623.6383-1-Sergey.Semin@baikalelectronics.ru 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.