summaryrefslogtreecommitdiff
diff options
context:
space:
mode:
authorNicolas Pitre <nicolas.pitre@linaro.org>2012-02-22 21:58:03 +0100
committerRussell King <rmk+kernel@arm.linux.org.uk>2012-03-24 09:38:55 +0000
commit9b5a146a43db3733c731d47022f4f5259e6b31e6 (patch)
tree3fc6d02c65c3f373d6408f9c332de183be7230b0
parent101d9b0dedbc9e560737d3357104bf09db48eb3e (diff)
downloadlinux-9b5a146a43db3733c731d47022f4f5259e6b31e6.tar.gz
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>
-rw-r--r--arch/arm/Kconfig.debug16
-rw-r--r--arch/arm/kernel/debug.S25
-rw-r--r--arch/arm/kernel/head.S8
3 files changed, 44 insertions, 5 deletions
diff --git a/arch/arm/Kconfig.debug b/arch/arm/Kconfig.debug
index e0d236d..755d9fb 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
diff --git a/arch/arm/kernel/debug.S b/arch/arm/kernel/debug.S
index 204e216..e5a765c 100644
--- a/arch/arm/kernel/debug.S
+++ b/arch/arm/kernel/debug.S
@@ -100,7 +100,7 @@
#endif /* CONFIG_CPU_V6 */
-#else
+#elif !defined(CONFIG_DEBUG_SEMIHOSTING)
#include <mach/debug-macro.S>
#endif /* CONFIG_DEBUG_ICEDCC */
@@ -155,6 +155,8 @@ hexbuf: .space 16
.ltorg
+#ifndef CONFIG_DEBUG_SEMIHOSTING
+
ENTRY(printascii)
addruart_current r3, r1, r2
b 2f
@@ -177,3 +179,24 @@ ENTRY(printch)
mov r0, #0
b 1b
ENDPROC(printch)
+
+#else
+
+ENTRY(printascii)
+ mov r1, r0
+ mov r0, #0x04 @ SYS_WRITE0
+ ARM( svc #0x123456 )
+ THUMB( svc #0xab )
+ mov pc, lr
+ENDPROC(printascii)
+
+ENTRY(printch)
+ adr r1, hexbuf
+ strb r0, [r1]
+ mov r0, #0x03 @ SYS_WRITEC
+ ARM( svc #0x123456 )
+ THUMB( svc #0xab )
+ mov pc, lr
+ENDPROC(printch)
+
+#endif
diff --git a/arch/arm/kernel/head.S b/arch/arm/kernel/head.S
index a2e9694..3bf0c7f 100644
--- a/arch/arm/kernel/head.S
+++ b/arch/arm/kernel/head.S
@@ -265,7 +265,7 @@ __create_page_tables:
str r6, [r3]
#ifdef CONFIG_DEBUG_LL
-#ifndef CONFIG_DEBUG_ICEDCC
+#if !defined(CONFIG_DEBUG_ICEDCC) && !defined(CONFIG_DEBUG_SEMIHOSTING)
/*
* Map in IO space for serial debugging.
* This allows debug messages to be output
@@ -297,10 +297,10 @@ __create_page_tables:
cmp r0, r6
blo 1b
-#else /* CONFIG_DEBUG_ICEDCC */
- /* we don't need any serial debugging mappings for ICEDCC */
+#else /* CONFIG_DEBUG_ICEDCC || CONFIG_DEBUG_SEMIHOSTING */
+ /* we don't need any serial debugging mappings */
ldr r7, [r10, #PROCINFO_IO_MMUFLAGS] @ io_mmuflags
-#endif /* !CONFIG_DEBUG_ICEDCC */
+#endif
#if defined(CONFIG_ARCH_NETWINDER) || defined(CONFIG_ARCH_CATS)
/*