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Diffstat (limited to 'Documentation/debugging-via-ohci1394.txt')
| -rw-r--r-- | Documentation/debugging-via-ohci1394.txt | 13 |
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: |