On Thu, Oct 20, 2022, Maxim Levitsky wrote:
> Add a few functions to apic.c to make it easier to enable and disable
> the local apic timer.
>
> Signed-off-by: Maxim Levitsky <mlevitsk@xxxxxxxxxx>
> ---
> lib/x86/apic.c | 37 +++++++++++++++++++++++++++++++++++++
> lib/x86/apic.h | 6 ++++++
> 2 files changed, 43 insertions(+)
>
> diff --git a/lib/x86/apic.c b/lib/x86/apic.c
> index 5131525a..dc6d3862 100644
> --- a/lib/x86/apic.c
> +++ b/lib/x86/apic.c
> @@ -256,3 +256,40 @@ void init_apic_map(void)
> id_map[j++] = i;
> }
> }
> +
> +void apic_setup_timer(int vector, bool periodic)
> +{
> + /* APIC runs with 'CPU core clock' divided by value in APIC_TDCR */
> +
> + u32 lvtt = vector |
> + (periodic ? APIC_LVT_TIMER_PERIODIC : APIC_LVT_TIMER_ONESHOT);
Rather than take @periodic, take the mode. That way this funky ternary operator
goes away and the callers are self-tdocumenting, e.g. this
apic_setup_timer(TIMER_VECTOR, APIC_LVT_TIMER_PERIODIC);
is more obvious than
apic_setup_timer(TIMER_VECTOR, true);
> +
> + apic_cleanup_timer();
> + apic_write(APIC_TDCR, APIC_TDR_DIV_1);
> + apic_write(APIC_LVTT, lvtt);
> +}
> +
> +void apic_start_timer(u32 counter)
> +{
> + apic_write(APIC_TMICT, counter);
> +}
> +
> +void apic_stop_timer(void)
> +{
> + apic_write(APIC_TMICT, 0);
> +}
> +
> +void apic_cleanup_timer(void)
> +{
> + u32 lvtt = apic_read(APIC_LVTT);
> +
> + // stop the counter
> + apic_stop_timer();
> +
> + // mask the timer interrupt
> + apic_write(APIC_LVTT, lvtt | APIC_LVT_MASKED);
> +
> + // ensure that a pending timer is serviced
> + irq_enable();
Jumping back to the "nop" patch, I'm reinforcing my vote to add sti_nop(). I
actually starting typing a response to say this is broken before remembering that
a nop got added to irq_enable().
> + irq_disable();
> +}
> diff --git a/lib/x86/apic.h b/lib/x86/apic.h
> index 6d27f047..db691e2a 100644
> --- a/lib/x86/apic.h
> +++ b/lib/x86/apic.h
> @@ -58,6 +58,12 @@ void disable_apic(void);
> void reset_apic(void);
> void init_apic_map(void);
>
> +void apic_cleanup_timer(void);
> +void apic_setup_timer(int vector, bool periodic);
> +
> +void apic_start_timer(u32 counter);
> +void apic_stop_timer(void);
> +
> /* Converts byte-addressable APIC register offset to 4-byte offset. */
> static inline u32 apic_reg_index(u32 reg)
> {
> --
> 2.26.3
>
