ttyFDC: Implement KGDB IO operations.
Implement KGDB IO operations for MIPS Fast Debug Channel (FDC). This can
be enabled via Kconfig, which also allows the channel number to be
chosen.
The magic sysrq hack is implemented in the TTY driver, detecting just ^C
for the KGDB channel, and ^O followed by a letter for the FDC console
channel.
The KGDB operations are reasonably efficient thanks to the flush
callback, with a 4 byte buffer being used in both directions to allow up
to 4 bytes to be encoded per FDC word. Reading of data for KGDB will
discard any data received on other channels, which clearly isn't ideal,
but given that there is a single FIFO shared between channels we can't
do much better.
Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Jiri Slaby <jslaby@suse.cz>
Cc: Jason Wessel <jason.wessel@windriver.com>
Cc: linux-mips@linux-mips.org
Cc: kgdb-bugreport@lists.sourceforge.net
Cc: linux-kernel@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/9147/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
diff --git a/drivers/tty/Kconfig b/drivers/tty/Kconfig
index e0c18e5..c01f450 100644
--- a/drivers/tty/Kconfig
+++ b/drivers/tty/Kconfig
@@ -450,4 +450,20 @@
If unsure, say N.
+config MIPS_EJTAG_FDC_KGDB
+ bool "Use KGDB over an FDC channel"
+ depends on MIPS_EJTAG_FDC_TTY && KGDB
+ default y
+ help
+ This enables the use of KGDB over an FDC channel, allowing KGDB to be
+ used remotely or when a serial port isn't available.
+
+config MIPS_EJTAG_FDC_KGDB_CHAN
+ int "KGDB FDC channel"
+ depends on MIPS_EJTAG_FDC_KGDB
+ range 2 15
+ default 3
+ help
+ FDC channel number to use for KGDB.
+
endif # TTY