c671b6dede
DMA on this hardware is limited to dealing with a 4096 bytes at a time. Previously, the driver was set up accordingly to request single-page DMA buffers, however that had the effect of generating a large number of small MMC requests for data I/O. Improve the driver to accept multi-entry scatter-gather lists. The size of each entry is already capped to 4096 bytes (AU6601_MAX_DMA_BLOCK_SIZE), matching the hardware requirements. Existing driver code already iterates through remaining sglist entries after each DMA transfer is complete. Also add some comments to help clarify the situation, and clear up some of the confusion I had regarding DMA vs PIO. Testing with dd, this increases write performance from 2mb/sec to 10mb/sec, and increases read performance from 4mb/sec to 14mb/sec. Signed-off-by: Daniel Drake <drake@endlessm.com> Link: http://lkml.kernel.org/r/CAD8Lp47JYdZzbV9F+asNwvSfLF_po_J7ir6R_Vb-Dab21_=Krw@mail.gmail.com Signed-off-by: Ulf Hansson <ulf.hansson@linaro.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.