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    Subject[PATCH 4.19 22/44] mips: loongson64: remove unreachable(), fix loongson_poweroff().
    Date
    4.19-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Yifeng Li <tomli@tomli.me>

    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.

    Reference: https://lkml.org/lkml/2019/2/5/908
    Signed-off-by: Yifeng Li <tomli@tomli.me>
    Signed-off-by: Paul Burton <paul.burton@mips.com>
    Cc: linux-mips@vger.kernel.org
    Cc: Huacai Chen <chenhc@lemote.com>
    Cc: Ralf Baechle <ralf@linux-mips.org>
    Cc: James Hogan <jhogan@kernel.org>
    Cc: linux-kernel@vger.kernel.org
    Cc: Aaro Koskinen <aaro.koskinen@iki.fi>
    Cc: stable@vger.kernel.org # v4.17+
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    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)
    {
    #ifndef CONFIG_LEFI_FIRMWARE_INTERFACE
    mach_prepare_shutdown();
    - unreachable();
    +
    + /*
    + * It needs a wait loop here, but mips/kernel/reset.c already calls
    + * a generic delay loop, machine_hang(), so simply return.
    + */
    + return;
    #else
    void (*fw_poweroff)(void) = (void *)loongson_sysconf.poweroff_addr;


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