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All UFS host controllers support DMA clustering. Hence enable DMA clustering. Notes: - The max_segment_size parameter implements the 256 KiB limit for the PRDT. The dma_boundary parameter represents a boundary that must not be crossed by DMA scatter/gather lists. I'm not aware of any restrictions on DMA scatter/gather lists in the UFSHCI specification other than the 256 KiB limit for the PRDT and the 32-bit address restriction for controllers that only support 32-bits DMA. The latter restriction is already handled by ufshcd_set_dma_mask(). - Without patch "scsi: ufs: exynos: Fix the maximum segment size", this patch breaks support for the Exynos controller. The history of the dma_boundary parameter in the UFS driver is as follows: * The initial UFS driver did not set the dma_boundary parameter. * Commit4dd4130a72("scsi: make sure all drivers set the use_clustering flag") set the .use_clustering flag. * Commit4af14d113b("scsi: remove the use_clustering flag") removed the use_clustering flag and set the dma_boundary parameter instead. Cc: Avri Altman <avri.altman@wdc.com> Cc: Alim Akhtar <alim.akhtar@samsung.com> Cc: Kiwoong Kim <kwmad.kim@samsung.com> Signed-off-by: Bart Van Assche <bvanassche@acm.org> Acked-by: Adrian Hunter <adrian.hunter@intel.com> Reviewed-by: Alim Akhtar <alim.akhtar@samsung.com> Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
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.