lkml.org 
[lkml]   [2021]   [Mar]   [18]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH] swiotlb: Add swiotlb=off to disable SWIOTLB
Date
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.fainelli@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
\
 
 \ /
  Last update: 2021-03-18 20:19    [W:0.190 / U:0.380 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site