summaryrefslogtreecommitdiffstats
path: root/Documentation/debugging-via-ohci1394.txt
diff options
context:
space:
mode:
Diffstat (limited to 'Documentation/debugging-via-ohci1394.txt')
-rw-r--r--Documentation/debugging-via-ohci1394.txt184
1 files changed, 0 insertions, 184 deletions
diff --git a/Documentation/debugging-via-ohci1394.txt b/Documentation/debugging-via-ohci1394.txt
deleted file mode 100644
index 611f5a5..0000000
--- a/Documentation/debugging-via-ohci1394.txt
+++ /dev/null
@@ -1,184 +0,0 @@
-
- Using physical DMA provided by OHCI-1394 FireWire controllers for debugging
- ---------------------------------------------------------------------------
-
-Introduction
-------------
-
-Basically all FireWire controllers which are in use today are compliant
-to the OHCI-1394 specification which defines the controller to be a PCI
-bus master which uses DMA to offload data transfers from the CPU and has
-a "Physical Response Unit" which executes specific requests by employing
-PCI-Bus master DMA after applying filters defined by the OHCI-1394 driver.
-
-Once properly configured, remote machines can send these requests to
-ask the OHCI-1394 controller to perform read and write requests on
-physical system memory and, for read requests, send the result of
-the physical memory read back to the requester.
-
-With that, it is possible to debug issues by reading interesting memory
-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.
-
-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
-buffer on to debug early boot problems in areas like ACPI where the system
-fails to boot and other means for debugging (serial port) are either not
-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
-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.
-
-Because ohci1394 and firewire-ohci depend 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.
-
-To activate it, enable CONFIG_PROVIDE_OHCI1394_DMA_INIT (Kernel hacking menu:
-Remote debugging over FireWire early on boot) and pass the parameter
-"ohci1394_dma=early" to the recompiled kernel on boot.
-
-Tools
------
-
-firescope - Originally developed by Benjamin Herrenschmidt, Andi Kleen ported
-it from PowerPC to x86 and x86_64 and added functionality, firescope can now
-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
-
-and he implemented fast system dump (alpha version - read README.txt):
-- http://halobates.de/firewire/firedump-0.1.tar.bz2
-
-There is also a gdb proxy for firewire which allows to use gdb to access
-data which can be referenced from symbols found by gdb in vmlinux:
-- http://halobates.de/firewire/fireproxy-0.33.tar.bz2
-
-The latest version of this gdb proxy (fireproxy-0.34) can communicate (not
-yet stable) with kgdb over an memory-based communication module (kgdbom).
-
-Getting Started
----------------
-
-The OHCI-1394 specification regulates that the OHCI-1394 controller must
-disable all physical DMA on each bus reset.
-
-This means that if you want to debug an issue in a system state where
-interrupts are disabled and where no polling of the OHCI-1394 controller
-for bus resets takes place, you have to establish any FireWire cable
-connections and fully initialize all FireWire hardware __before__ the
-system enters such state.
-
-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.
- 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]
-
- 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
- specification are available. If it requires no driver for Windows operating
- systems, it most likely is. Only specialized shops have cards which are not
- compliant, they are based on TI PCILynx chips and require drivers for Win-
- dows operating systems.
-
-2) Establish a working FireWire cable connection:
-
- Any FireWire cable, as long at it provides electrically and mechanically
- stable connection and has matching connectors (there are small 4-pin and
- large 6-pin FireWire ports) will do.
-
- If an driver is running on both machines you should see a line like
-
- ieee1394: Node added: ID:BUS[0-01:1023] GUID[0090270001b84bba]
-
- 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,
- then start firescope:
-
- $ firescope
- Port 0 (ohci1394) opened, 2 nodes detected
-
- FireScope
- ---------
- Target : <unspecified>
- Gen : 1
- [Ctrl-T] choose target
- [Ctrl-H] this menu
- [Ctrl-Q] quit
-
- ------> Press Ctrl-T now, the output should be similar to:
-
- 2 nodes available, local node is: 0
- 0: ffc0, uuid: 00000000 00000000 [LOCAL]
- 1: ffc1, uuid: 00279000 ba4bb801
-
- Besides the [LOCAL] node, it must show another node without error message.
-
-4) Prepare for debugging with early OHCI-1394 initialization:
-
- 4.1) Kernel compilation and installation on debug target
-
- Compile the kernel to be debugged with CONFIG_PROVIDE_OHCI1394_DMA_INIT
- (Kernel hacking: Provide code for enabling DMA over FireWire early on boot)
- enabled and install it on the machine to be debugged (debug target).
-
- 4.2) Transfer the System.map of the debugged kernel to the debug host
-
- Copy the System.map of the kernel be debugged to the debug host (the host
- which is connected to the debugged machine over the FireWire cable).
-
-5) Retrieving the printk buffer contents:
-
- With the FireWire cable connected, the OHCI-1394 driver on the debugging
- host loaded, reboot the debugged machine, booting the kernel which has
- CONFIG_PROVIDE_OHCI1394_DMA_INIT enabled, with the option ohci1394_dma=early.
-
- Then, on the debugging host, run firescope, for example by using -A:
-
- firescope -A System.map-of-debug-target-kernel
-
- Note: -A automatically attaches to the first non-local node. It only works
- reliably if only connected two machines are connected using FireWire.
-
- After having attached to the debug target, press Ctrl-D to view the
- complete printk buffer or Ctrl-U to enter auto update mode and get an
- updated live view of recent kernel messages logged on the debug target.
-
- Call "firescope -h" to get more information on firescope's options.
-
-Notes
------
-Documentation and specifications: http://halobates.de/firewire/
-
-FireWire is a trademark of Apple Inc. - for more information please refer to:
-http://en.wikipedia.org/wiki/FireWire