path: root/Documentation/kernel-parameters.txt
diff options
authorGeert Uytterhoeven <geert+renesas@glider.be>2016-12-16 14:28:42 +0100
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2017-01-26 08:24:44 +0100
commit41c6b3e8989e79772a50429d92cf91959bcce96d (patch)
treee1098b8fb35ab3f524703d89c01d885c6ed76d54 /Documentation/kernel-parameters.txt
parent1fd1e6cd63143cf5d198a536d875dfc88ce179bc (diff)
swiotlb: Add swiotlb=noforce debug option
commit fff5d99225107f5f13fe4a9805adc2a1c4b5fb00 upstream. 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> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'Documentation/kernel-parameters.txt')
1 files changed, 2 insertions, 1 deletions
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 37babf91f2cb..922dec8fa07e 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -3998,10 +3998,11 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
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]