3 files changed, 31 insertions, 7 deletions

diff --git a/Documentation/debugging-via-ohci1394.txt b/Documentation/debugging-via-ohci1394.txt
index c360d4e91b48..59a91e5c6909 100644
--- a/Documentation/debugging-via-ohci1394.txt
+++ b/Documentation/debugging-via-ohci1394.txt
@@ -41,15 +41,19 @@ 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, hence is not yet suitable for remote debugging.
+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 depends on the PCI enumeration to be completed, an
-initialization routine which runs pretty early (long before console_init()
-which makes the printk buffer appear on the console can be called) was written.
+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:
-Provide code for enabling DMA over FireWire early on boot) and pass the
-parameter "ohci1394_dma=early" to the recompiled kernel on boot.
+Remote debugging over FireWire early on boot) and pass the parameter
+"ohci1394_dma=early" to the recompiled kernel on boot.
 
 Tools
 -----
diff --git a/drivers/firewire/fw-ohci.c b/drivers/firewire/fw-ohci.c
index 07d6053ff57e..5da7c6715e1e 100644
--- a/drivers/firewire/fw-ohci.c
+++ b/drivers/firewire/fw-ohci.c
@@ -1097,6 +1097,11 @@ static void bus_reset_tasklet(unsigned long data)
                 reg_write(ohci, OHCI1394_ConfigROMhdr, ohci->next_header);
         }
 
+#ifdef CONFIG_FIREWIRE_OHCI_REMOTE_DMA
+        reg_write(ohci, OHCI1394_PhyReqFilterHiSet, ~0);
+        reg_write(ohci, OHCI1394_PhyReqFilterLoSet, ~0);
+#endif
+
         spin_unlock_irqrestore(&ohci->lock, flags);
 
         if (free_rom)
@@ -1435,6 +1440,9 @@ static int ohci_cancel_packet(struct fw_card *card, struct fw_packet *packet)
 static int
 ohci_enable_phys_dma(struct fw_card *card, int node_id, int generation)
 {
+#ifdef CONFIG_FIREWIRE_OHCI_REMOTE_DMA
+        return 0;
+#else
         struct fw_ohci *ohci = fw_ohci(card);
         unsigned long flags;
         int n, retval = 0;
@@ -1466,6 +1474,7 @@ ohci_enable_phys_dma(struct fw_card *card, int node_id, int generation)
  out:
         spin_unlock_irqrestore(&ohci->lock, flags);
         return retval;
+#endif /* CONFIG_FIREWIRE_OHCI_REMOTE_DMA */
 }
 
 static u64
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 0796c1a090c0..78955eb6bd94 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -593,7 +593,7 @@ config LATENCYTOP
           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"
+        bool "Remote debugging over FireWire early on boot"
         depends on PCI && X86
         help
           If you want to debug problems which hang or crash the kernel early
@@ -621,4 +621,15 @@ config PROVIDE_OHCI1394_DMA_INIT
 
           See Documentation/debugging-via-ohci1394.txt for more information.
 
+config FIREWIRE_OHCI_REMOTE_DMA
+        bool "Remote debugging over FireWire with firewire-ohci"
+        depends on FIREWIRE_OHCI
+        help
+          This option lets you use the FireWire bus for remote debugging
+          with help of the firewire-ohci driver. It enables unfiltered
+          remote DMA in firewire-ohci.
+          See Documentation/debugging-via-ohci1394.txt for more information.
+
+          If unsure, say N.
+
 source "samples/Kconfig"