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authorAkinobu Mita <akinobu.mita@gmail.com>2014-06-04 16:06:54 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2014-06-04 16:53:57 -0700
commit5ea3b1b2f8ad9162684431ce6188102ca4c64b7a (patch)
treefe87b74396be16d20025673adf39ed607d7e3b92 /Documentation
parent2bfc2862c4fe38379a2fb2cfba33fad32ccb4ff4 (diff)
downloadlinux-5ea3b1b2f8ad9162684431ce6188102ca4c64b7a.tar.bz2
cma: add placement specifier for "cma=" kernel parameter
Currently, "cma=" kernel parameter is used to specify the size of CMA, but we can't specify where it is located. We want to locate CMA below 4GB for devices only supporting 32-bit addressing on 64-bit systems without iommu. This enables to specify the placement of CMA by extending "cma=" kernel parameter. Examples: 1. locate 64MB CMA below 4GB by "cma=64M@0-4G" 2. locate 64MB CMA exact at 512MB by "cma=64M@512M" Note that the DMA contiguous memory allocator on x86 assumes that page_address() works for the pages to allocate. So this change requires to limit end address of contiguous memory area upto max_pfn_mapped to prevent from locating it on highmem area by the argument of dma_contiguous_reserve(). Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com> Cc: Marek Szyprowski <m.szyprowski@samsung.com> Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> Cc: David Woodhouse <dwmw2@infradead.org> Cc: Don Dutile <ddutile@redhat.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@redhat.com> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Yinghai Lu <yinghai@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'Documentation')
-rw-r--r--Documentation/kernel-parameters.txt7
1 files changed, 5 insertions, 2 deletions
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index af55e13ace8f..adea3a22fa00 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -630,8 +630,11 @@ 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
+ cma=nn[MG]@[start[MG][-end[MG]]]
+ [ARM,X86,KNL]
+ 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
include/linux/dma-contiguous.h