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authorGeert Uytterhoeven <geert+renesas@glider.be>2016-12-16 16:28:42 +0300
committerKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>2016-12-19 17:05:20 +0300
commitfff5d99225107f5f13fe4a9805adc2a1c4b5fb00 (patch)
tree0b9748236ea4580bc44f9a24ec27c215cb46ed9b /Documentation
parentae7871be189cb41184f1e05742b4a99e2c59774d (diff)
downloadlinux-fff5d99225107f5f13fe4a9805adc2a1c4b5fb00.tar.xz
swiotlb: Add swiotlb=noforce debug option
On architectures like arm64, swiotlb is tied intimately to the core architecture DMA support. In addition, ZONE_DMA cannot be disabled. To aid debugging and catch devices not supporting DMA to memory outside the 32-bit address space, add a kernel command line option "swiotlb=noforce", which disables the use of bounce buffers. If specified, trying to map memory that cannot be used with DMA will fail, and a rate-limited warning will be printed. Note that io_tlb_nslabs is set to 1, which is the minimal supported value. Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Diffstat (limited to 'Documentation')
-rw-r--r--Documentation/admin-guide/kernel-parameters.txt3
1 files changed, 2 insertions, 1 deletions
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index be2d6d0a03a4..7d5f4f4cecfa 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -3807,10 +3807,11 @@
it if 0 is given (See Documentation/cgroup-v1/memory.txt)
swiotlb= [ARM,IA-64,PPC,MIPS,X86]
- Format: { <int> | force }
+ Format: { <int> | force | noforce }
<int> -- Number of I/O TLB slabs
force -- force using of bounce buffers even if they
wouldn't be automatically used by the kernel
+ noforce -- Never use bounce buffers (for debugging)
switches= [HW,M68k]