qemu: Implement qemu_system_off via semihosting.

This makes the PSCI SYSTEM_OFF call work on QEMU. It assumes that QEMU has
semihosting enabled, but that is already assumed by the image loader.
Signed-off-by: Andrew Walbran <qwandor@google.com>
Change-Id: I0fb7cf7909262b675c3143efeac07f4d60730b03

include/lib/semihosting.h

@@ -23,6 +23,7 @@
 #define SEMIHOSTING_SYS_REMOVE          0x0E
 #define SEMIHOSTING_SYS_SYSTEM          0x12
 #define SEMIHOSTING_SYS_ERRNO           0x13
+#define SEMIHOSTING_SYS_EXIT            0x18
 
 #define FOPEN_MODE_R			0x0
 #define FOPEN_MODE_RB			0x1
@@ -54,5 +55,6 @@ long semihosting_download_file(const char *file_name,
 void semihosting_write_char(char character);
 void semihosting_write_string(char *string);
 char semihosting_read_char(void);
+void semihosting_exit(uint32_t reason, uint32_t subcode);
 
 #endif /* SEMIHOSTING_H */

lib/semihosting/semihosting.c

@@ -15,7 +15,7 @@
 #endif
 
 long semihosting_call(unsigned long operation,
-			void *system_block_address);
+			uintptr_t system_block_address);
 
 typedef struct {
 	const char *file_name;
@@ -53,7 +53,7 @@ long semihosting_file_open(const char *file_name, size_t mode)
 	open_block.name_length = strlen(file_name);
 
 	return semihosting_call(SEMIHOSTING_SYS_OPEN,
-				(void *) &open_block);
+				(uintptr_t) &open_block);
 }
 
 long semihosting_file_seek(long file_handle, ssize_t offset)
@@ -65,7 +65,7 @@ long semihosting_file_seek(long file_handle, ssize_t offset)
 	seek_block.location = offset;
 
 	result = semihosting_call(SEMIHOSTING_SYS_SEEK,
-				  (void *) &seek_block);
+				  (uintptr_t) &seek_block);
 
 	if (result)
 		result = semihosting_call(SEMIHOSTING_SYS_ERRNO, 0);
@@ -86,7 +86,7 @@ long semihosting_file_read(long file_handle, size_t *length, uintptr_t buffer)
 	read_block.length = *length;
 
 	result = semihosting_call(SEMIHOSTING_SYS_READ,
-				  (void *) &read_block);
+				  (uintptr_t) &read_block);
 
 	if (result == *length) {
 		return -EINVAL;
@@ -112,7 +112,7 @@ long semihosting_file_write(long file_handle,
 	write_block.length = *length;
 
 	result = semihosting_call(SEMIHOSTING_SYS_WRITE,
-				   (void *) &write_block);
+				   (uintptr_t) &write_block);
 
 	*length = result;
 
@@ -122,28 +122,28 @@ long semihosting_file_write(long file_handle,
 long semihosting_file_close(long file_handle)
 {
 	return semihosting_call(SEMIHOSTING_SYS_CLOSE,
-				(void *) &file_handle);
+				(uintptr_t) &file_handle);
 }
 
 long semihosting_file_length(long file_handle)
 {
 	return semihosting_call(SEMIHOSTING_SYS_FLEN,
-				(void *) &file_handle);
+				(uintptr_t) &file_handle);
 }
 
 char semihosting_read_char(void)
 {
-	return semihosting_call(SEMIHOSTING_SYS_READC, NULL);
+	return semihosting_call(SEMIHOSTING_SYS_READC, 0);
 }
 
 void semihosting_write_char(char character)
 {
-	semihosting_call(SEMIHOSTING_SYS_WRITEC, (void *) &character);
+	semihosting_call(SEMIHOSTING_SYS_WRITEC, (uintptr_t) &character);
 }
 
 void semihosting_write_string(char *string)
 {
-	semihosting_call(SEMIHOSTING_SYS_WRITE0, (void *) string);
+	semihosting_call(SEMIHOSTING_SYS_WRITE0, (uintptr_t) string);
 }
 
 long semihosting_system(char *command_line)
@@ -154,7 +154,7 @@ long semihosting_system(char *command_line)
 	system_block.command_length = strlen(command_line);
 
 	return semihosting_call(SEMIHOSTING_SYS_SYSTEM,
-				(void *) &system_block);
+				(uintptr_t) &system_block);
 }
 
 long semihosting_get_flen(const char *file_name)
@@ -216,3 +216,15 @@ semihosting_fail:
 	semihosting_file_close(file_handle);
 	return ret;
 }
+
+void semihosting_exit(uint32_t reason, uint32_t subcode)
+{
+#ifdef __aarch64__
+	uint64_t parameters[] = {reason, subcode};
+
+	(void) semihosting_call(SEMIHOSTING_SYS_EXIT, (uintptr_t) &parameters);
+#else
+	/* The subcode is not supported on AArch32. */
+	(void) semihosting_call(SEMIHOSTING_SYS_EXIT, reason);
+#endif
+}

plat/qemu/common/qemu_pm.c

@@ -10,10 +10,13 @@
 #include <arch_helpers.h>
 #include <common/debug.h>
 #include <lib/psci/psci.h>
+#include <lib/semihosting.h>
 #include <plat/common/platform.h>
 
 #include "qemu_private.h"
 
+#define ADP_STOPPED_APPLICATION_EXIT 0x20026
+
 /*
  * The secure entry point to be used on warm reset.
  */
@@ -191,7 +194,8 @@ void qemu_pwr_domain_suspend_finish(const psci_power_state_t *target_state)
  ******************************************************************************/
 static void __dead2 qemu_system_off(void)
 {
-	ERROR("QEMU System Off: operation not handled.\n");
+	semihosting_exit(ADP_STOPPED_APPLICATION_EXIT, 0);
+	ERROR("QEMU System Off: semihosting call unexpectedly returned.\n");
 	panic();
 }
 

plat/qemu/qemu/platform.mk

@@ -151,6 +151,8 @@ ifeq (${ARM_ARCH_MAJOR},8)
 BL31_SOURCES		+=	lib/cpus/aarch64/aem_generic.S		\
 				lib/cpus/aarch64/cortex_a53.S		\
 				lib/cpus/aarch64/cortex_a57.S		\
+				lib/semihosting/semihosting.c		\
+				lib/semihosting/${ARCH}/semihosting_call.S \
 				plat/common/plat_psci_common.c		\
 				${PLAT_QEMU_COMMON_PATH}/qemu_pm.c			\
 				${PLAT_QEMU_COMMON_PATH}/topology.c			\

plat/qemu/qemu_sbsa/platform.mk

@@ -71,6 +71,8 @@ QEMU_GIC_SOURCES	:=	drivers/arm/gic/v3/gicv3_helpers.c		\
 BL31_SOURCES		+=	lib/cpus/aarch64/aem_generic.S			\
 				lib/cpus/aarch64/cortex_a53.S			\
 				lib/cpus/aarch64/cortex_a57.S			\
+				lib/semihosting/semihosting.c			\
+				lib/semihosting/${ARCH}/semihosting_call.S	\
 				plat/common/plat_psci_common.c			\
 				${PLAT_QEMU_COMMON_PATH}/qemu_pm.c		\
 				${PLAT_QEMU_COMMON_PATH}/topology.c		\