It may be useful to disable the SWIOTLB completely for testing or when a platform is known not to have any DRAM addressing limitations what so ever.
Signed-off-by: Florian Fainelli <f.faine...@gmail.com> --- Documentation/admin-guide/kernel-parameters.txt | 1 + include/linux/swiotlb.h | 1 + kernel/dma/swiotlb.c | 9 +++++++++ 3 files changed, 11 insertions(+) diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 04545725f187..b0223e48921e 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -5278,6 +5278,7 @@ force -- force using of bounce buffers even if they wouldn't be automatically used by the kernel noforce -- Never use bounce buffers (for debugging) + off -- Completely disable SWIOTLB switches= [HW,M68k] diff --git a/include/linux/swiotlb.h b/include/linux/swiotlb.h index 5857a937c637..23f86243defe 100644 --- a/include/linux/swiotlb.h +++ b/include/linux/swiotlb.h @@ -15,6 +15,7 @@ enum swiotlb_force { SWIOTLB_NORMAL, /* Default - depending on HW DMA mask etc. */ SWIOTLB_FORCE, /* swiotlb=force */ SWIOTLB_NO_FORCE, /* swiotlb=noforce */ + SWIOTLB_OFF, /* swiotlb=off */ }; /* diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c index c10e855a03bc..d7a4a789c7d3 100644 --- a/kernel/dma/swiotlb.c +++ b/kernel/dma/swiotlb.c @@ -126,6 +126,8 @@ setup_io_tlb_npages(char *str) } else if (!strcmp(str, "noforce")) { swiotlb_force = SWIOTLB_NO_FORCE; io_tlb_nslabs = 1; + } else if (!strcmp(str, "off")) { + swiotlb_force = SWIOTLB_OFF; } return 0; @@ -229,6 +231,9 @@ int __init swiotlb_init_with_tbl(char *tlb, unsigned long nslabs, int verbose) unsigned long i, bytes; size_t alloc_size; + if (swiotlb_force == SWIOTLB_OFF) + return 0; + bytes = nslabs << IO_TLB_SHIFT; io_tlb_nslabs = nslabs; @@ -284,6 +289,9 @@ swiotlb_init(int verbose) unsigned char *vstart; unsigned long bytes; + if (swiotlb_force == SWIOTLB_OFF) + goto out; + if (!io_tlb_nslabs) { io_tlb_nslabs = (default_size >> IO_TLB_SHIFT); io_tlb_nslabs = ALIGN(io_tlb_nslabs, IO_TLB_SEGSIZE); @@ -302,6 +310,7 @@ swiotlb_init(int verbose) io_tlb_start = 0; } pr_warn("Cannot allocate buffer"); +out: no_iotlb_memory = true; } -- 2.25.1 _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu