Retrieving a full system memory dump is also possible over the FireWire,
using data transfer rates in the order of 10MB/s or more.
-Memory access is currently limited to the low 4G of physical address
-space which 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 hardware based on x86, x86-64 and PowerPC.
+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.
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
The firewire-ohci driver in drivers/firewire uses filtered physical
DMA by default, which is more secure but not suitable for remote debugging.
-Compile the driver with CONFIG_FIREWIRE_OHCI_REMOTE_DMA (Kernel hacking menu:
-Remote debugging over FireWire with firewire-ohci) to get unfiltered physical
-DMA.
+Pass the remote_dma=1 parameter to the driver to get unfiltered physical DMA.
Because the firewire-ohci driver depends on the PCI enumeration to be
completed, an initialization routine which runs pretty early has been
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.
+
2) Establish a working FireWire cable connection:
Any FireWire cable, as long at it provides electrically and mechanically