2ff25c1c32
Current way we find a waiting virtual channel for the next transfer at the time one physical channel becomes free is not really fair. More in details, in case there is more than one channel waiting at a time, by just going through the arrays of memcpy and slave channels and stopping as soon as state match waiting state, channels with high indexes can be penalized. Whenever dma engine is substantially overloaded so that we constantly get several channels waiting, channels with highest indexes might not be served for a substantial time which in the worse case, might hang task that wait for dma transfer to complete. This patch makes physical channel re-assignment more fair by storing time in jiffies when a channel is put in waiting state. Whenever a physical channel has to be re-assigned, this time is used to select channel that is waiting for the longest time. Signed-off-by: Jean-Nicolas Graux <jean-nicolas.graux@st.com> Reviewed-by: Linus Walleij <linus.walleij@linaro.org> Reviewed-by: Nicolas Guion <nicolas.guion@st.com> 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.