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SubjectRe: [PATCH v1] arm: clocksource: Check if timer is enabled for timer irq
On Thu, 11 Aug 2022 10:36:20 +0100,
Ayan Kumar Halder <ayankuma@amd.com> wrote:
>
> Refer ARM DDI 0487G.b, CNTP_CTL_EL0,
> ISTATUS, bit [2] - When the value of the ENABLE bit is 1, ISTATUS
> indicates whether the timer condition is met.
>
> Thus, one need to check ENABLE bit along with ISTATUS, to confirm
> whether the timer condition is met. Further as the doc says,
> "When the value of the ENABLE bit is 0, the ISTATUS field is UNKNOWN."
>
> Signed-off-by: Ayan Kumar Halder <ayankuma@amd.com>
> ---
>
> Please refer to https://lore.kernel.org/all/6cfcd4fa-3afd-1c70-6a70-9df557ee1811@xen.org/T/
> for the previous discussion on this issue on xen-devel mailing list.
>
> drivers/clocksource/arm_arch_timer.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/clocksource/arm_arch_timer.c b/drivers/clocksource/arm_arch_timer.c
> index 9ab8221ee3c6..96921772814c 100644
> --- a/drivers/clocksource/arm_arch_timer.c
> +++ b/drivers/clocksource/arm_arch_timer.c
> @@ -647,7 +647,7 @@ static __always_inline irqreturn_t timer_handler(const int access,
> unsigned long ctrl;
>
> ctrl = arch_timer_reg_read(access, ARCH_TIMER_REG_CTRL, evt);
> - if (ctrl & ARCH_TIMER_CTRL_IT_STAT) {
> + if ((ctrl & ARCH_TIMER_CTRL_IT_STAT) && (ctrl & ARCH_TIMER_CTRL_ENABLE)) {
> ctrl |= ARCH_TIMER_CTRL_IT_MASK;
> arch_timer_reg_write(access, ARCH_TIMER_REG_CTRL, ctrl, evt);
> evt->event_handler(evt);

And how can the timer be disabled if we're in the interrupt handler?

M.

--
Without deviation from the norm, progress is not possible.

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