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SubjectRe: [PATCH v2 4/5] ARC: MCIP: Set an initial affinity value in idu_irq_map
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On 10/24/2016 05:46 AM, Yuriy Kolerov wrote:
> Originally an initial distribution mode (its value resides in Device Tree)
> for each common interrupt is set in idu_irq_xlate. This leads to the
> following problems. idu_irq_xlate may be called several times during parsing
> of the Device Tree and it is semantically wrong to configure an initial
> distribution mode here. Also a value of affinity (CPUs bitmap) is not saved
> to irq_desc structure for the virq - later (after parsing of the DT) kernel
> sees that affinity is not set and sets a default value of affinity (all
> cores in round robin mode). As a result a value of affinity from Device
> Tree is ignored.
>
> To fix it I created a buffer for initial CPUs bitmaps from Device Tree.
> In idu_irq_xlate those bitmaps are saved to the buffer. Then affinity
> for virq is set manually in idu_irq_map. It works because idu_irq_xlate
> is always called before idu_irq_map.
>
> Despite the fact that it works I think that it must be rewritten to
> eliminate usage of the buffer and move all logic to idu_irq_map but
> I do not know how to do it correctly.
>
> Signed-off-by: Yuriy Kolerov <yuriy.kolerov@synopsys.com>
> ---
> arch/arc/kernel/mcip.c | 15 +++++++++++----
> 1 file changed, 11 insertions(+), 4 deletions(-)
>
> diff --git a/arch/arc/kernel/mcip.c b/arch/arc/kernel/mcip.c
> index 51a218c..090f0a1 100644
> --- a/arch/arc/kernel/mcip.c
> +++ b/arch/arc/kernel/mcip.c
> @@ -12,12 +12,15 @@
> #include <linux/irq.h>
> #include <linux/spinlock.h>
> #include <linux/irqdomain.h>
> +#include <linux/interrupt.h>
> +#include <linux/cpumask.h>
> #include <asm/irqflags-arcv2.h>
> #include <asm/mcip.h>
> #include <asm/setup.h>
>
> static char smp_cpuinfo_buf[128];
> static int idu_detected;
> +static unsigned long idu_cirq_to_dest[CONFIG_ARC_NUMBER_OF_INTERRUPTS];
>
> static DEFINE_RAW_SPINLOCK(mcip_lock);
>
> @@ -232,9 +235,15 @@ static void idu_cascade_isr(struct irq_desc *desc)
>
> static int idu_irq_map(struct irq_domain *d, unsigned int virq, irq_hw_number_t hwirq)
> {
> + cpumask_t mask;
> +
> irq_set_chip_and_handler(virq, &idu_irq_chip, handle_level_irq);
> irq_set_status_flags(virq, IRQ_MOVE_PCNTXT);
>
> + cpumask_clear(&mask);
> + cpumask_bits(&mask)[0] |= idu_cirq_to_dest[hwirq];
> + irq_set_affinity(virq, &mask);
> +
> return 0;
> }
>
> @@ -252,8 +261,7 @@ static int idu_irq_xlate(struct irq_domain *d, struct device_node *n,
> if (distri == 0) {
> /* 0 - Round Robin to all cpus, otherwise 1 bit per core */
> raw_spin_lock_irqsave(&mcip_lock, flags);
> - idu_set_dest(hwirq, BIT(num_online_cpus()) - 1);
> - idu_set_mode(hwirq, IDU_M_TRIG_LEVEL, IDU_M_DISTRI_RR);
> + idu_cirq_to_dest[hwirq] = BIT(num_online_cpus()) - 1;
> raw_spin_unlock_irqrestore(&mcip_lock, flags);
> } else {
> /*
> @@ -267,8 +275,7 @@ static int idu_irq_xlate(struct irq_domain *d, struct device_node *n,
> hwirq, cpu);
>
> raw_spin_lock_irqsave(&mcip_lock, flags);
> - idu_set_dest(hwirq, cpu);
> - idu_set_mode(hwirq, IDU_M_TRIG_LEVEL, IDU_M_DISTRI_DEST);
> + idu_cirq_to_dest[hwirq] = cpu;
> raw_spin_unlock_irqrestore(&mcip_lock, flags);
> }
>

So I missed this part - you are not touching the hardware here at all - and so we
don't really need the spin lock check. Nevertheless, as you said off list, this
patch is more of a hack and we really need to find a saner way of doing this !

@Marc, @tglx any guidance here - changelog at the top has the motivation for this
hack !

Thx,
-Vineet

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