Commit 9b5a146a authored by Nicolas Pitre's avatar Nicolas Pitre Committed by Russell King
Browse files

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: default avatarNicolas Pitre <nicolas.pitre@linaro.org>
Signed-off-by: default avatarRussell King <rmk+kernel@arm.linux.org.uk>
parent 101d9b0d

arch/arm/Kconfig.debug

+16 −0
Original line number Diff line number Diff line
@@ -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

arch/arm/kernel/debug.S

+24 −1
Original line number Diff line number Diff line
@@ -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

arch/arm/kernel/head.S

+4 −4
Original line number Diff line number Diff line
@@ -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)

	/*

CRA Git | Maintained and supported by SUSTech CRA and CCSE