diff options
Diffstat (limited to 'Documentation/debugging-via-ohci1394.txt')
| -rw-r--r-- | Documentation/debugging-via-ohci1394.txt | 41 |
1 files changed, 19 insertions, 22 deletions
diff --git a/Documentation/debugging-via-ohci1394.txt b/Documentation/debugging-via-ohci1394.txt index 611f5a5499b1..fa0151a712f9 100644 --- a/Documentation/debugging-via-ohci1394.txt +++ b/Documentation/debugging-via-ohci1394.txt @@ -22,10 +22,12 @@ locations such as buffers like the printk buffer or the process table. 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 @@ -36,17 +38,11 @@ available (notebooks) or too slow for extensive debug information (like ACPI). Drivers ------- -The ohci1394 driver in drivers/ieee1394 initializes the OHCI-1394 controllers -to a working state and enables physical DMA by default for all remote nodes. -This can be turned off by ohci1394's module parameter phys_dma=0. - -The alternative firewire-ohci driver in drivers/firewire uses filtered physical +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 ohci1394 and firewire-ohci depend on the PCI enumeration to be +Because the firewire-ohci driver depends on the PCI enumeration to be completed, an initialization routine which runs pretty early has been implemented for x86. This routine runs long before console_init() can be called, i.e. before the printk buffer appears on the console. @@ -64,7 +60,7 @@ be used to view the printk buffer of a remote machine, even with live update. Bernhard Kaindl enhanced firescope to support accessing 64-bit machines from 32-bit firescope and vice versa: -- http://halobates.de/firewire/firescope-0.2.2.tar.bz2 +- http://v3.sk/~lkundrak/firescope/ and he implemented fast system dump (alpha version - read README.txt): - http://halobates.de/firewire/firedump-0.1.tar.bz2 @@ -92,11 +88,11 @@ Step-by-step instructions for using firescope with early OHCI initialization: 1) Verify that your hardware is supported: - Load the ohci1394 or the fw-ohci module and check your kernel logs. + Load the firewire-ohci module and check your kernel logs. You should see a line similar to - ohci1394: fw-host0: OHCI-1394 1.1 (PCI): IRQ=[18] MMIO=[fe9ff800-fe9fffff] - ... Max Packet=[2048] IR/IT contexts=[4/8] + firewire_ohci 0000:15:00.1: added OHCI v1.0 device as card 2, 4 IR + 4 IT + ... contexts, quirks 0x11 when loading the driver. If you have no supported controller, many PCI, CardBus and even some Express cards which are fully compliant to OHCI-1394 @@ -105,6 +101,9 @@ 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. + 2) Establish a working FireWire cable connection: Any FireWire cable, as long at it provides electrically and mechanically @@ -113,20 +112,18 @@ Step-by-step instructions for using firescope with early OHCI initialization: If an driver is running on both machines you should see a line like - ieee1394: Node added: ID:BUS[0-01:1023] GUID[0090270001b84bba] + firewire_core 0000:15:00.1: created device fw1: GUID 00061b0020105917, S400 on both machines in the kernel log when the cable is plugged in and connects the two machines. 3) Test physical DMA using firescope: - On the debug host, - - load the raw1394 module, - - make sure that /dev/raw1394 is accessible, + On the debug host, make sure that /dev/fw* is accessible, then start firescope: $ firescope - Port 0 (ohci1394) opened, 2 nodes detected + Port 0 (/dev/fw1) opened, 2 nodes detected FireScope --------- |