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-rw-r--r--lib/Kconfig.debug28
1 files changed, 28 insertions, 0 deletions
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index aa56e631580d..89f4035b526c 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -586,5 +586,33 @@ config LATENCYTOP
Enable this option if you want to use the LatencyTOP tool
to find out which userspace is blocking on what kernel operations.
+config PROVIDE_OHCI1394_DMA_INIT
+ bool "Provide code for enabling DMA over FireWire early on boot"
+ depends on PCI && X86
+ help
+ If you want to debug problems which hang or crash the kernel early
+ on boot and the crashing machine has a FireWire port, you can use
+ this feature to remotely access the memory of the crashed machine
+ over FireWire. This employs remote DMA as part of the OHCI1394
+ specification which is now the standard for FireWire controllers.
+
+ With remote DMA, you can monitor the printk buffer remotely using
+ firescope and access all memory below 4GB using fireproxy from gdb.
+ Even controlling a kernel debugger is possible using remote DMA.
+
+ Usage:
+
+ If ohci1394_dma=early is used as boot parameter, it will initialize
+ all OHCI1394 controllers which are found in the PCI config space.
+
+ As all changes to the FireWire bus such as enabling and disabling
+ devices cause a bus reset and thereby disable remote DMA for all
+ devices, be sure to have the cable plugged and FireWire enabled on
+ the debugging host before booting the debug target for debugging.
+
+ This code (~1k) is freed after boot. By then, the firewire stack
+ in charge of the OHCI-1394 controllers should be used instead.
+
+ See Documentation/debugging-via-ohci1394.txt for more information.
source "samples/Kconfig"