Hi Nick,
On Mon, Jun 12, 2017 at 09:58:25AM +1000, Nicholas Piggin wrote:
> When the CPU wakes from low power state, it begins at the system reset
> interrupt with the exception that caused the wakeup encoded in SRR1.
>
> Today, powernv idle wakeup ignores the wakeup reason (except a special
> case for HMI), and the regular interrupt corresponding to the
> exception will fire after the idle wakeup exits.
>
> Change this to replay the interrupt from the idle wakeup before
> interrupts are hard-enabled.
>
> Test on POWER8 of context_switch selftests benchmark with polling idle
> disabled (e.g., always nap, giving cross-CPU IPIs) gives the following
> results:
>
> original wakeup direct
> Different threads, same core: 315k/s 264k/s
> Different cores: 235k/s 242k/s
>
> There is a slowdown for doorbell IPI (same core) case because system
> reset wakeup does not clear the message and the doorbell interrupt
> fires again needlessly.
Should we clear the doorbell message if we are recording the fact that
the Doorbell irq has happened in paca ?
>
> Signed-off-by: Nicholas Piggin <npig...@gmail.com>
> ---
> arch/powerpc/include/asm/hw_irq.h | 2 ++
> arch/powerpc/kernel/irq.c | 25 +++++++++++++++++++++++++
> arch/powerpc/platforms/powernv/idle.c | 10 ++++++++--
> 3 files changed, 35 insertions(+), 2 deletions(-)
>
> diff --git a/arch/powerpc/include/asm/hw_irq.h
> b/arch/powerpc/include/asm/hw_irq.h
> index f06112cf8734..8366bdc69988 100644
[..snip..]
> --- a/arch/powerpc/kernel/irq.c
> +++ b/arch/powerpc/kernel/irq.c
> @@ -348,6 +348,7 @@ bool prep_irq_for_idle(void)
> return true;
> }
>
> +#ifdef CONFIG_PPC_BOOK3S
> /*
> * This is for idle sequences that return with IRQs off, but the
> * idle state itself wakes on interrupt. Tell the irq tracer that
> @@ -379,6 +380,30 @@ bool prep_irq_for_idle_irqsoff(void)
> }
>
> /*
> + * Take the SRR1 wakeup reason, index into this table to find the
> + * appropriate irq_happened bit.
> + */
> +static const u8 srr1_to_irq[0x10] = {
> + 0, 0, 0,
> + PACA_IRQ_DBELL,
> + 0,
> + PACA_IRQ_DBELL,
> + PACA_IRQ_DEC,
> + 0,
> + PACA_IRQ_EE,
> + PACA_IRQ_EE,
> + PACA_IRQ_HMI,
> + 0, 0, 0, 0, 0 };
> +
> +void irq_set_pending_from_srr1(unsigned long srr1)
> +{
> + unsigned int idx = (srr1 >> 18) & SRR1_WAKEMASK_P8;
Shouldn't this be
unsigned int idx = (srr1 & SRR1_WAKEMASK_P8) >> 18;
?
> +
> + local_paca->irq_happened |= srr1_to_irq[idx];
> +}
> +#endif /* CONFIG_PPC_BOOK3S */
> +
Looks good otherwise.
--
Thanks and Regards
gautham.
