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| author | Nicolas Pitre <nicolas.pitre@linaro.org> | 2012-02-23 00:58:03 +0400 |
|---|---|---|
| committer | Russell King <rmk+kernel@arm.linux.org.uk> | 2012-03-24 13:38:55 +0400 |
| commit | 9b5a146a43db3733c731d47022f4f5259e6b31e6 (patch) | |
| tree | 3fc6d02c65c3f373d6408f9c332de183be7230b0 | |
| parent | 101d9b0dedbc9e560737d3357104bf09db48eb3e (diff) | |
| download | linux-9b5a146a43db3733c731d47022f4f5259e6b31e6.tar.xz | |
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.debug | 16 | ||||
| -rw-r--r-- | arch/arm/kernel/debug.S | 25 | ||||
| -rw-r--r-- | arch/arm/kernel/head.S | 8 |
3 files changed, 44 insertions, 5 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 diff --git a/arch/arm/kernel/debug.S b/arch/arm/kernel/debug.S index 204e2160cfcc..e5a765c5f06a 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 a2e9694a68ee..3bf0c7f8b043 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) /* |