drivers: add Contiguous Memory Allocator

The Contiguous Memory Allocator is a set of helper functions for DMA
mapping framework that improves allocations of contiguous memory chunks.

CMA grabs memory on system boot, marks it with MIGRATE_CMA migrate type
and gives back to the system. Kernel is allowed to allocate only movable
pages within CMA's managed memory so that it can be used for example for
page cache when DMA mapping do not use it. On
dma_alloc_from_contiguous() request such pages are migrated out of CMA
area to free required contiguous block and fulfill the request. This
allows to allocate large contiguous chunks of memory at any time
assuming that there is enough free memory available in the system.

This code is heavily based on earlier works by Michal Nazarewicz.

Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: Michal Nazarewicz <mina86@mina86.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Tested-by: Rob Clark <rob.clark@linaro.org>
Tested-by: Ohad Ben-Cohen <ohad@wizery.com>
Tested-by: Benjamin Gaignard <benjamin.gaignard@linaro.org>
Tested-by: Robert Nelson <robertcnelson@gmail.com>
Tested-by: Barry Song <Baohua.Song@csr.com>

1 files changed, 5 insertions, 0 deletions

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index c1601e5a8b71..669e8bb52b94 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -508,6 +508,11 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
                         Also note the kernel might malfunction if you disable
                         some critical bits.
 
+        cma=nn[MG]      [ARM,KNL]
+                        Sets the size of kernel global memory area for contiguous
+                        memory allocations. For more information, see
+                        include/linux/dma-contiguous.h
+
         cmo_free_hint=  [PPC] Format: { yes | no }
                         Specify whether pages are marked as being inactive
                         when they are freed.  This is used in CMO environments