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authorAnton Vorontsov <anton.vorontsov@linaro.org>2012-09-24 14:27:56 -0700
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2012-09-26 13:52:36 -0700
commit0c57dfcc6c1d037243c2f8fbf62eab3633326ec0 (patch)
tree0cbdffff6807949c49b49190188d295d489b0c66 /tools/testing
parent5c8124a0f8f50c5671b028b7a030d893a3a1a539 (diff)
downloadblackbird-op-linux-0c57dfcc6c1d037243c2f8fbf62eab3633326ec0.tar.gz
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tty/serial: Add kgdb_nmi driver
This special driver makes it possible to temporary use NMI debugger port as a normal console by issuing 'nmi_console' command (assuming that the port is attached to KGDB). Unlike KDB's disable_nmi command, with this driver you are always able to go back to the debugger using KGDB escape sequence ($3#33). This is because this console driver processes the input in NMI context, and thus is able to intercept the magic sequence. Note that since the console interprets input and uses polling communication methods, for things like PPP it is still better to fully detach debugger port from the KGDB NMI (i.e. disable_nmi), and use raw console. Usually, to enter the debugger one have to type the magic sequence, so initially the kernel will print the following prompt on the NMI debugger console: Type $3#33 to enter the debugger> For convenience, there is a kgdb_fiq.knock kernel command line option, when set to 0, this turns the special command to just a return key press, so the kernel will be printing this: Hit <return> to enter the debugger> This is more convenient for long debugging sessions, although it makes nmi_console feature somewhat useless. And for the cases when NMI connected to a dedicated button, the knocking can be disabled altogether by setting kgdb_fiq.knock to -1. Suggested-by: Colin Cross <ccross@android.com> Signed-off-by: Anton Vorontsov <anton.vorontsov@linaro.org> Acked-by: Alan Cox <alan@linux.intel.com> Acked-by: Jason Wessel <jason.wessel@windriver.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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