a94a098a21
The sun4i DMA engine supports transfer sizes up to 128k for normal DMA and 16M for dedicated DMA, as documented in the A10 and A20 manuals. Since this is larger than the default segment size limit (64k), exposing the real limit reduces the number of transfers needed for a transaction. However, because the device can only report one segment size limit, we have to expose the smaller limit from normal DMA. One complication is that the driver combines pairs of periodic transfers to reduce programming overhead. This only works when the period size is at most half of the maximum transfer size. With the default 64k segment size limit, this was always the case, but for normal DMA it is no longer guaranteed. Skip the optimization if the period is too long; even without it, the overhead is less than before. Signed-off-by: Samuel Holland <samuel@sholland.org> Link: https://lore.kernel.org/r/20220621031350.36187-1-samuel@sholland.org Signed-off-by: Vinod Koul <vkoul@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.