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"