ARM: 7338/1: add support for early console output via semihosting

This is a very simple method for code running in an emulator, or under
the supervision of a debugger, to use I/O facilities on the controlling
host.

Tested with OpenOCD, and ARM's Fast Models.

Details on semihosting can be found in chapter 8 of
DUI0203I_rvct_developer_guide.pdf from ARM Ltd.

Signed-off-by: Nicolas Pitre <nicolas.pitre@linaro.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

1 files changed, 16 insertions, 0 deletions

diff --git a/arch/arm/Kconfig.debug b/arch/arm/Kconfig.debug
index e0d236d7ff73..755d9fbe3238 100644
--- a/arch/arm/Kconfig.debug
+++ b/arch/arm/Kconfig.debug
@@ -100,6 +100,22 @@ choice
                   Note that the system will appear to hang during boot if there
                   is nothing connected to read from the DCC.
 
+        config DEBUG_SEMIHOSTING
+                bool "Kernel low-level debug output via semihosting I"
+                help
+                  Semihosting enables code running on an ARM target to use
+                  the I/O facilities on a host debugger/emulator through a
+                  simple SVC calls. The host debugger or emulator must have
+                  semihosting enabled for the special svc call to be trapped
+                  otherwise the kernel will crash.
+
+                  This is known to work with OpenOCD, as wellas
+                  ARM's Fast Models, or any other controlling environment
+                  that implements semihosting.
+
+                  For more details about semihosting, please see
+                  chapter 8 of DUI0203I_rvct_developer_guide.pdf from ARM Ltd.
+
         config AT91_DEBUG_LL_DBGU0
                 bool "Kernel low-level debugging on rm9200, 9260/9g20, 9261/9g10 and 9rl"
                 depends on HAVE_AT91_DBGU0