powerpc: Document xmon options

Document all options currently supported by xmon debugger.

Signed-off-by: Gustavo Romero <gromero@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20190814205638.25322-1-gromero@linux.ibm.com

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 7ccd158b3894e7841f16c11597ddbcadf1f7c34d..6d495aab4d0b46dba853c9d7004850bc532b6974 100644 (file)
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -5305,3 +5305,22 @@
                        A hex value specifying bitmask with supplemental xhci
                        host controller quirks. Meaning of each bit can be
                        consulted in header drivers/usb/host/xhci.h.
+
+       xmon            [PPC]
+                       Format: { early | on | rw | ro | off }
+                       Controls if xmon debugger is enabled. Default is off.
+                       Passing only "xmon" is equivalent to "xmon=early".
+                       early   Call xmon as early as possible on boot; xmon
+                               debugger is called from setup_arch().
+                       on      xmon debugger hooks will be installed so xmon
+                               is only called on a kernel crash. Default mode,
+                               i.e. either "ro" or "rw" mode, is controlled
+                               with CONFIG_XMON_DEFAULT_RO_MODE.
+                       rw      xmon debugger hooks will be installed so xmon
+                               is called only on a kernel crash, mode is write,
+                               meaning SPR registers, memory and, other data
+                               can be written using xmon commands.
+                       ro      same as "rw" option above but SPR registers,
+                               memory, and other data can't be written using
+                               xmon commands.
+                       off     xmon is disabled.