[PATCH] CMA: Document cma=0

From: Jean Delvare
Date: Sat Oct 04 2014 - 08:36:52 EST


It isn't obvious that CMA can be disabled on the kernel's command
line, so document it.

Signed-off-by: Jean Delvare <jdelvare@xxxxxxx>
Cc: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
Documentation/kernel-parameters.txt | 3 ++-
drivers/base/Kconfig | 3 +++
2 files changed, 5 insertions(+), 1 deletion(-)

--- linux-3.17-rc7.orig/Documentation/kernel-parameters.txt 2014-09-23 13:19:06.644838292 +0200
+++ linux-3.17-rc7/Documentation/kernel-parameters.txt 2014-10-04 14:10:03.257579721 +0200
@@ -656,7 +656,8 @@ bytes respectively. Such letter suffixes
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 }
--- linux-3.17-rc7.orig/drivers/base/Kconfig 2014-09-12 16:23:14.911353676 +0200
+++ linux-3.17-rc7/drivers/base/Kconfig 2014-10-04 13:41:37.672347240 +0200
@@ -231,6 +231,9 @@ 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".



--
Jean Delvare
SUSE L3 Support
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