[PATCH 3/4] microblaze: reset: Provide a power off handler through an unaligned PC

microblaze is missing a generic architecture-wide power off mechanism.

To enable KUnit for microblaze it is necessary for KUnit to shut down
the machine in a way that QEMU will recognize. The machines emulated by
QEMU do not provide machine-specific power off functionality which could
be used.
However at least the petalogix-s3adsp1800 machine will abort if an
unaligned instruction is executed. An ugly message will be printed but
that is not an issue for KUnit.

Make use of this to provide a power off handler.

Signed-off-by: Thomas Weißschuh <[email protected]>

---
This is quite hacky. But I didn't find a better solution.
---
 arch/microblaze/Kconfig        |  9 +++++++++
 arch/microblaze/kernel/reset.c | 21 +++++++++++++++++++++
 2 files changed, 30 insertions(+)

diff --git a/arch/microblaze/Kconfig b/arch/microblaze/Kconfig
index 484ebb3baedf..0ca8999dd770 100644
--- a/arch/microblaze/Kconfig
+++ b/arch/microblaze/Kconfig
@@ -216,3 +216,12 @@ config MB_MANAGER
 	  Say N here unless you know what you are doing.
 
 endmenu
+
+config MB_POWER_OFF_THROUGH_UNALIGNED_PC
+	bool "Power off through unaligned PC"
+	help
+	  This options adds a power off handler which executes an unaligned PC
+	  so the machine resets in a generic way. This works for the
+	  petalogix-s3adsp1800 QEMU machine.
+
+	  Say N here unless you know what you are doing.
diff --git a/arch/microblaze/kernel/reset.c b/arch/microblaze/kernel/reset.c
index 3612a20ca16d..4af660deed3b 100644
--- a/arch/microblaze/kernel/reset.c
+++ b/arch/microblaze/kernel/reset.c
@@ -41,3 +41,24 @@ void machine_restart(char *cmd)
 	pr_emerg("Reboot failed -- System halted\n");
 	while (1);
 }
+
+#ifdef CONFIG_MB_POWER_OFF_THROUGH_UNALIGNED_PC
+static int unaligned_pc_sys_off(struct sys_off_data *data)
+{
+	__asm__(
+		"bri 1\n"
+	);
+
+	return NOTIFY_DONE;
+}
+
+static int __init register_unaligned_pc_sys_off(void)
+{
+	struct sys_off_handler *sys_off;
+
+	sys_off = register_sys_off_handler(SYS_OFF_MODE_POWER_OFF, SYS_OFF_PRIO_LOW,
+					   unaligned_pc_sys_off, NULL);
+	return PTR_ERR_OR_ZERO(sys_off);
+}
+device_initcall(register_unaligned_pc_sys_off);
+#endif /* CONFIG_MB_POWER_OFF_THROUGH_UNALIGNED_PC */

-- 
2.55.0