[Feature]add MT2731_MP2_MR2_SVN388 baseline version
Change-Id: Ief04314834b31e27effab435d3ca8ba33b499059
diff --git a/src/kernel/linux/v4.14/Documentation/debugging-via-ohci1394.txt b/src/kernel/linux/v4.14/Documentation/debugging-via-ohci1394.txt
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+===========================================================================
+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.
+
+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.
+
+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
+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 firewire-ohci driver in drivers/firewire uses filtered physical
+DMA by default, which is more secure but not suitable for remote debugging.
+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
+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://v3.sk/~lkundrak/firescope/
+
+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 firewire-ohci module and check your kernel logs.
+ You should see a line similar to::
+
+ 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
+ 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 Windows
+ operating systems.
+
+ 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:
+
+ 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::
+
+ 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, make sure that /dev/fw* is accessible,
+ then start firescope::
+
+ $ firescope
+ Port 0 (/dev/fw1) 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:
+https://en.wikipedia.org/wiki/FireWire