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SubjectRe: [PATCH v2 5/5] ARC: MCIP: Use IDU_M_DISTRI_DEST mode if there is only 1 destination core
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On 10/24/2016 05:46 AM, Yuriy Kolerov wrote:
> ARC linux uses 2 distribution modes for common interrupts: round robin
> mode (IDU_M_DISTRI_RR) and a simple destination mode (IDU_M_DISTRI_DEST).
> The first one is used when more than 1 cores may handle a common interrupt
> and the second one is used when only 1 core may handle a common interrupt.
>
> However idu_irq_set_affinity always sets IDU_M_DISTRI_RR for all affinity
> values. But there is no sense in setting of such mode if only 1 core must
> handle a common interrupt.
>
> Signed-off-by: Yuriy Kolerov <yuriy.kolerov@synopsys.com>
> ---
> arch/arc/kernel/mcip.c | 11 +++++++++--
> 1 file changed, 9 insertions(+), 2 deletions(-)
>
> diff --git a/arch/arc/kernel/mcip.c b/arch/arc/kernel/mcip.c
> index 090f0a1..75e6d73 100644
> --- a/arch/arc/kernel/mcip.c
> +++ b/arch/arc/kernel/mcip.c
> @@ -197,6 +197,7 @@ idu_irq_set_affinity(struct irq_data *data, const struct cpumask *cpumask,
> {
> unsigned long flags;
> cpumask_t online;
> + unsigned long dest_bits;
>
> /* errout if no online cpu per @cpumask */
> if (!cpumask_and(&online, cpumask, cpu_online_mask))
> @@ -204,8 +205,14 @@ idu_irq_set_affinity(struct irq_data *data, const struct cpumask *cpumask,
>
> raw_spin_lock_irqsave(&mcip_lock, flags);
>
> - idu_set_dest(data->hwirq, cpumask_bits(&online)[0]);
> - idu_set_mode(data->hwirq, IDU_M_TRIG_LEVEL, IDU_M_DISTRI_RR);
> + dest_bits = cpumask_bits(&online)[0];
> + idu_set_dest(data->hwirq, dest_bits);
> +
> + if (ffs(dest_bits) == fls(dest_bits)) {
> + idu_set_mode(data->hwirq, IDU_M_TRIG_LEVEL, IDU_M_DISTRI_DEST);
> + } else {
> + idu_set_mode(data->hwirq, IDU_M_TRIG_LEVEL, IDU_M_DISTRI_RR);
> + }

Better to use a local variable to assign IDU_M_xxx and then call idu_set_mode()
outside the if. I know the compiler would do that anyways, but that looks simpler
to read !

But on the other hand, adding all of this here - isn't there some sort of
duplication of code now between here and in the idu_irq_xlate() ?
Do we need the same stuff in 2 places ?

>
> raw_spin_unlock_irqrestore(&mcip_lock, flags);
>
>

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