This is a note to let you know that I've just added the patch titled
clocksource/drivers/arm_arch_timer: Disable timer before programming CVAL
to the 6.5-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
clocksource-drivers-arm_arch_timer-disable-timer-before-programming-cval.patch
and it can be found in the queue-6.5 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From e7d65e40ab5a5940785c5922f317602d0268caaf Mon Sep 17 00:00:00 2001
From: Walter Chang <walter.chang@xxxxxxxxxxxx>
Date: Mon, 17 Jul 2023 17:07:34 +0800
Subject: clocksource/drivers/arm_arch_timer: Disable timer before programming CVAL
From: Walter Chang <walter.chang@xxxxxxxxxxxx>
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@xxxxxxxxxxxxxxx
Signed-off-by: Walter Chang <walter.chang@xxxxxxxxxxxx>
Acked-by: Marc Zyngier <maz@xxxxxxxxxx>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@xxxxxxxxxxxxx>
Signed-off-by: Daniel Lezcano <daniel.lezcano@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20230717090735.19370-1-walter.chang@xxxxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
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
@@ -792,6 +792,13 @@ 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;
Patches currently in stable-queue which might be from walter.chang@xxxxxxxxxxxx are
queue-6.5/clocksource-drivers-arm_arch_timer-disable-timer-before-programming-cval.patch
