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SubjectRe: [PATCH v2 4/4] ARCv2: IRQ: Set a default priority for all core interrupts
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On 01/31/2017 03:45 AM, Yuriy Kolerov wrote:
> After reset all interrupts in the core interrupt controller has
> the highest priority P0. If the platform supports Fast IRQs and
> has more than 1 banks of registers then CPU automatically switch
> banks of registers when P0 interrupt comes.
>
> The problem is that the kernel expects that by default switching
> of banks is not used by all interrupts. It is necessary to set a
> default nonzero priority for all available interrupts to avoid
> undefined behaviour.
>
> Signed-off-by: Yuriy Kolerov <yuriy.kolerov@synopsys.com>
> ---
> arch/arc/kernel/intc-arcv2.c | 12 +++++++++++-
> 1 file changed, 11 insertions(+), 1 deletion(-)
>
> diff --git a/arch/arc/kernel/intc-arcv2.c b/arch/arc/kernel/intc-arcv2.c
> index 31246cc..d4fa4a5 100644
> --- a/arch/arc/kernel/intc-arcv2.c
> +++ b/arch/arc/kernel/intc-arcv2.c
> @@ -22,7 +22,7 @@
> */
> void arc_init_IRQ(void)
> {
> - unsigned int tmp, irq_prio;
> + unsigned int tmp, irq_prio, i;
>
> struct bcr_irq_arcv2 irq_bcr;
>
> @@ -62,6 +62,16 @@ void arc_init_IRQ(void)
> irq_prio + 1, ARCV2_IRQ_DEF_PRIO,
> irq_bcr.firq ? " FIRQ (not used)":"");
>
> + /*
> + * Set a default priority for all available interrupts to prevent
> + * switching of register banks if Fast IRQ and multiple register banks
> + * are supported by CPU.
> + */
> + for (i = NR_EXCEPTIONS; i < irq_bcr.irqs + NR_EXCEPTIONS; i++) {
> + write_aux_reg(AUX_IRQ_SELECT, i);
> + write_aux_reg(AUX_IRQ_PRIORITY, ARCV2_IRQ_DEF_PRIO);
> + }
> +

This itself is fine. However going forward can we move to the genirq
irq_cpu_online() etc instead of doing this in our platform per cpu hook ?

https://www.linux-mips.org/archives/linux-mips/2011-03/msg00115.html


> /* setup status32, don't enable intr yet as kernel doesn't want */
> tmp = read_aux_reg(ARC_REG_STATUS32);
> tmp |= STATUS_AD_MASK | (ARCV2_IRQ_DEF_PRIO << 1);
>

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