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Subject[PATCH 4.20 27/50] mips: loongson64: remove unreachable(), fix loongson_poweroff().
4.20-stable review patch.  If anyone has any objections, please let me know.


From: Yifeng Li <>

commit 8a96669d77897ff3613157bf43f875739205d66d upstream.

On my Yeeloong 8089, I noticed the machine fails to shutdown
properly, and often, the function mach_prepare_reboot() is
unexpectedly executed, thus the machine reboots instead. A
wait loop is needed to ensure the system is in a well-defined
state before going down.

In commit 997e93d4df16 ("MIPS: Hang more efficiently on
halt/powerdown/restart"), a general superset of the wait loop for all
platforms is already provided, so we don't need to implement our own.

This commit simply removes the unreachable() compiler marco after
mach_prepare_reboot(), thus allowing the execution of machine_hang().
My test shows that the machine is now able to shutdown successfully.

Please note that there are two different bugs preventing the machine
from shutting down, another work-in-progress commit is needed to
fix a lockup in cpufreq / i8259 driver, please read Reference, this
commit does not fix that bug.

Signed-off-by: Yifeng Li <>
Signed-off-by: Paul Burton <>
Cc: Huacai Chen <>
Cc: Ralf Baechle <>
Cc: James Hogan <>
Cc: Aaro Koskinen <>
Cc: # v4.17+
Signed-off-by: Greg Kroah-Hartman <>

arch/mips/loongson64/common/reset.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)

--- a/arch/mips/loongson64/common/reset.c
+++ b/arch/mips/loongson64/common/reset.c
@@ -59,7 +59,12 @@ static void loongson_poweroff(void)
- unreachable();
+ /*
+ * It needs a wait loop here, but mips/kernel/reset.c already calls
+ * a generic delay loop, machine_hang(), so simply return.
+ */
+ return;
void (*fw_poweroff)(void) = (void *)loongson_sysconf.poweroff_addr;

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