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So far a bounce buffer is used to serialize the scatterlist(s). This overhead can be avoided by switching to descriptor chain mode. As result the performance is drastically improved. On a Odroid-C2 with a 128 GB eMMC module raw reads reach 140 MB/s. Prerequisite for descriptor chain mode is that all scatterlist buffers are 8 byte aligned for 64-bit DMA. That's not always the case, at least the brcmfmac SDIO WiFi driver is known to cause problems. Therefore, for each request, check upfront whether all scatterlist buffers are 8 byte aligned and fall back to bounce buffer mode if that's not the case. Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com> Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. 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.