soc: qcom: smp2p: Safely acquire spinlock without IRQs

commit fc3e62e2 upstream.

smp2p_update_bits() should disable interrupts when it acquires its
spinlock. This is important because without the _irqsave, a priority
inversion can occur.

This function is called both with interrupts enabled in
qcom_q6v5_request_stop(), and with interrupts disabled in
ipa_smp2p_panic_notifier(). IRQ handling of spinlocks should be
consistent to avoid the panic notifier deadlocking because it's
sitting on the thread that's already got the lock via _request_stop().

Found via lockdep.

Cc: stable@vger.kernel.org
Fixes: 50e99641 ("soc: qcom: smp2p: Qualcomm Shared Memory Point to Point")
Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Reviewed-by: Stephen Boyd <swboyd@chromium.org>
Signed-off-by: Evan Green <evgreen@chromium.org>
Link: https://lore.kernel.org/r/20200929133040.RESEND.1.Ideabf6dcdfc577cf39ce3d95b0e4aa1ac8b38f0c@changeid


Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>