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authorLinus Torvalds <torvalds@linux-foundation.org>2014-05-30 23:06:15 +0400
committerLinus Torvalds <torvalds@linux-foundation.org>2014-05-30 23:06:15 +0400
commit1326af2464fc29290d1710447297d33a90a6ece4 (patch)
treed052eeff789e56a83dd881ef6efa809f73e28b43 /Documentation
parent24e19d279f9e289e965b4bc4710fbccab824c4c4 (diff)
parent2fe2023adf695d08af5b598b2be3b288a95d563c (diff)
downloadlinux-1326af2464fc29290d1710447297d33a90a6ece4.tar.xz
Merge tag 'firewire-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/ieee1394/linux1394
Pull firewire fix from Stefan Richter: "A regression fix for the IEEE 1394 subsystem: re-enable IRQ-based asynchronous request reception at addresses below 128 TB" * tag 'firewire-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/ieee1394/linux1394: firewire: revert to 4 GB RDMA, fix protocols using Memory Space
Diffstat (limited to 'Documentation')
-rw-r--r--Documentation/debugging-via-ohci1394.txt13
1 files changed, 8 insertions, 5 deletions
diff --git a/Documentation/debugging-via-ohci1394.txt b/Documentation/debugging-via-ohci1394.txt
index fa0151a712f9..5c9a567b3fac 100644
--- a/Documentation/debugging-via-ohci1394.txt
+++ b/Documentation/debugging-via-ohci1394.txt
@@ -25,9 +25,11 @@ using data transfer rates in the order of 10MB/s or more.
With most FireWire controllers, memory access is limited to the low 4 GB
of physical address space. This can be a problem on IA64 machines where
memory is located mostly above that limit, but it is rarely a problem on
-more common hardware such as x86, x86-64 and PowerPC. However, at least
-Agere/LSI FW643e and FW643e2 controllers are known to support access to
-physical addresses above 4 GB.
+more common hardware such as x86, x86-64 and PowerPC.
+
+At least LSI FW643e and FW643e2 controllers are known to support access to
+physical addresses above 4 GB, but this feature is currently not enabled by
+Linux.
Together with a early initialization of the OHCI-1394 controller for debugging,
this facility proved most useful for examining long debugs logs in the printk
@@ -101,8 +103,9 @@ Step-by-step instructions for using firescope with early OHCI initialization:
compliant, they are based on TI PCILynx chips and require drivers for Win-
dows operating systems.
- The mentioned kernel log message contains ">4 GB phys DMA" in case of
- OHCI-1394 controllers which support accesses above this limit.
+ The mentioned kernel log message contains the string "physUB" if the
+ controller implements a writable Physical Upper Bound register. This is
+ required for physical DMA above 4 GB (but not utilized by Linux yet).
2) Establish a working FireWire cable connection: