From f0d6d1f6ff6f8525cfa396ec1969b8f402391445 Mon Sep 17 00:00:00 2001
From: Jean Delvare <jdelvare@suse.de>
Date: Thu, 9 Oct 2014 15:29:41 -0700
Subject: [PATCH] CMA: document cma=0
It isn't obvious that CMA can be disabled on the kernel's command line, so
document it.
Signed-off-by: Jean Delvare <jdelvare@suse.de>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Akinobu Mita <akinobu.mita@gmail.com>
Cc: Chuck Ebbert <cebbert.lkml@gmail.com>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
Documentation/kernel-parameters.txt | 3 ++-
drivers/base/Kconfig | 3 +++
2 files changed, 5 insertions(+), 1 deletion(-)
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index a126a31dde020..809e880bc7876 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -656,7 +656,8 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
Sets the size of kernel global memory area for
contiguous memory allocations and optionally the
placement constraint by the physical address range of
- memory allocations. For more information, see
+ memory allocations. A value of 0 disables CMA
+ altogether. For more information, see
include/linux/dma-contiguous.h
cmo_free_hint= [PPC] Format: { yes | no }
diff --git a/drivers/base/Kconfig b/drivers/base/Kconfig
index 134f763d90fda..61a33f4ba608c 100644
--- a/drivers/base/Kconfig
+++ b/drivers/base/Kconfig
@@ -252,6 +252,9 @@ config DMA_CMA
to allocate big physically-contiguous blocks of memory for use with
hardware components that do not support I/O map nor scatter-gather.
+ You can disable CMA by specifying "cma=0" on the kernel's command
+ line.
+
For more information see <include/linux/dma-contiguous.h>.
If unsure, say "n".
--
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