[PATCH] irqchip: omap-intc: improve IRQ handler

[Tony Lindgren]

* Felipe Balbi <balbi at ti.com> [150102 10:50]:
> as it turns out the current IRQ number will
> *always* be available from SIR register which
> renders the reads of PENDING registers as plain
> unnecessary overhead.
> 
> In order to catch any situation where SIR reads
> as zero, we're adding a WARN() to turn it into
> a very verbose error and users actually report
> it.
> 
> With this patch average running time of
> omap_intc_handle_irq() reduced from about 28.5us
> to 19.8us as measured by the kernel function
> profiler.

That's a nice improvment for an interrupt controller :)
 
> Tested with BeagleBoneBlack Rev A5C.
> 
> Signed-off-by: Felipe Balbi <balbi at ti.com>
> ---
> 
> Before applying, it would be very nice to get reports
> from other folks on different platforms, specially OMAP2/3
> ones which I don't have (easy) access.

Seems to behave just fine on omap2 and 3 here, gave it
a quick try on n800, n900, omap3-ldp and 37xx-evm:

Tested-by: Tony Lindgren <tony at atomide.com>

Regards,

Tony
 
>  drivers/irqchip/irq-omap-intc.c | 35 +++++------------------------------
>  1 file changed, 5 insertions(+), 30 deletions(-)
> 
> diff --git a/drivers/irqchip/irq-omap-intc.c b/drivers/irqchip/irq-omap-intc.c
> index 28718d3..a2da6d5 100644
> --- a/drivers/irqchip/irq-omap-intc.c
> +++ b/drivers/irqchip/irq-omap-intc.c
> @@ -315,37 +315,12 @@ static int __init omap_init_irq(u32 base, struct device_node *node)
>  static asmlinkage void __exception_irq_entry
>  omap_intc_handle_irq(struct pt_regs *regs)
>  {
> -	u32 irqnr = 0;
> -	int handled_irq = 0;
> -	int i;
> -
> -	do {
> -		for (i = 0; i < omap_nr_pending; i++) {
> -			irqnr = intc_readl(INTC_PENDING_IRQ0 + (0x20 * i));
> -			if (irqnr)
> -				goto out;
> -		}
> -
> -out:
> -		if (!irqnr)
> -			break;
> -
> -		irqnr = intc_readl(INTC_SIR);
> -		irqnr &= ACTIVEIRQ_MASK;
> +	u32 irqnr;
>  
> -		if (irqnr) {
> -			handle_domain_irq(domain, irqnr, regs);
> -			handled_irq = 1;
> -		}
> -	} while (irqnr);
> -
> -	/*
> -	 * If an irq is masked or deasserted while active, we will
> -	 * keep ending up here with no irq handled. So remove it from
> -	 * the INTC with an ack.
> -	 */
> -	if (!handled_irq)
> -		omap_ack_irq(NULL);
> +	irqnr = intc_readl(INTC_SIR);
> +	irqnr &= ACTIVEIRQ_MASK;
> +	WARN(!irqnr, "Spuriour IRQ ?\n");
> +	handle_domain_irq(domain, irqnr, regs);
>  }
>  
>  void __init omap2_init_irq(void)
> -- 
> 2.2.0
>