tree 4b3b9d25a9c8fa850ddc7c9fca63abf10de0dbd7
parent 33298ef6d8ddef57aaa1d11ed53fc08bef2f95aa
author Doug Anderson <armlinux@m.disordat.com> 1454105246 +0100
committer Russell King <rmk+kernel@arm.linux.org.uk> 1455204818 +0000

ARM: 8506/1: common: DMA-mapping: add DMA_ATTR_ALLOC_SINGLE_PAGES attribute

This patch adds the DMA_ATTR_ALLOC_SINGLE_PAGES attribute to the
DMA-mapping subsystem.

This attribute can be used as a hint to the DMA-mapping subsystem that
it's likely not worth it to try to allocate large pages behind the
scenes.  Large pages are likely to make an IOMMU TLB work more
efficiently but may not be worth it.  See the Documentation contained in
this patch for more details about this attribute and when to use it.

Note that the name of the hint (DMA_ATTR_ALLOC_SINGLE_PAGES) is loosely
based on the name MADV_NOHUGEPAGE.  Just as there is MADV_NOHUGEPAGE
vs. MADV_HUGEPAGE we could also add an "opposite" attribute to
DMA_ATTR_ALLOC_SINGLE_PAGES.  Without having the "opposite" attribute
the lack of DMA_ATTR_ALLOC_SINGLE_PAGES means "use your best judgement
about whether to use small pages or large pages".

Signed-off-by: Douglas Anderson <dianders@chromium.org>
Acked-by: Marek Szyprowski <m.szyprowski@samsung.com>
Reviewed-by: Robin Murphy <robin.murphy@arm.com>
Tested-by: Javier Martinez Canillas <javier@osg.samsung.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>