6.1-stable review patch. If anyone has any objections, please let me know.
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From: Walter Chang walter.chang@mediatek.com
commit e7d65e40ab5a5940785c5922f317602d0268caaf upstream.
Due to the fact that the use of `writeq_relaxed()` to program CVAL is not guaranteed to be atomic, it is necessary to disable the timer before programming CVAL.
However, if the MMIO timer is already enabled and has not yet expired, there is a possibility of unexpected behavior occurring: when the CPU enters the idle state during this period, and if the CPU's local event is earlier than the broadcast event, the following process occurs:
tick_broadcast_enter() tick_broadcast_oneshot_control(TICK_BROADCAST_ENTER) __tick_broadcast_oneshot_control() ___tick_broadcast_oneshot_control() tick_broadcast_set_event() clockevents_program_event() set_next_event_mem()
During this process, the MMIO timer remains enabled while programming CVAL. To prevent such behavior, disable timer explicitly prior to programming CVAL.
Fixes: 8b82c4f883a7 ("clocksource/drivers/arm_arch_timer: Move MMIO timer programming over to CVAL") Cc: stable@vger.kernel.org Signed-off-by: Walter Chang walter.chang@mediatek.com Acked-by: Marc Zyngier maz@kernel.org Reviewed-by: AngeloGioacchino Del Regno angelogioacchino.delregno@collabora.com Signed-off-by: Daniel Lezcano daniel.lezcano@linaro.org Link: https://lore.kernel.org/r/20230717090735.19370-1-walter.chang@mediatek.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/clocksource/arm_arch_timer.c | 7 +++++++ 1 file changed, 7 insertions(+)
--- a/drivers/clocksource/arm_arch_timer.c +++ b/drivers/clocksource/arm_arch_timer.c @@ -773,6 +773,13 @@ static __always_inline void set_next_eve u64 cnt;
ctrl = arch_timer_reg_read(access, ARCH_TIMER_REG_CTRL, clk); + + /* Timer must be disabled before programming CVAL */ + if (ctrl & ARCH_TIMER_CTRL_ENABLE) { + ctrl &= ~ARCH_TIMER_CTRL_ENABLE; + arch_timer_reg_write(access, ARCH_TIMER_REG_CTRL, ctrl, clk); + } + ctrl |= ARCH_TIMER_CTRL_ENABLE; ctrl &= ~ARCH_TIMER_CTRL_IT_MASK;