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Commit d3b421cd authored by Sekhar Nori's avatar Sekhar Nori Committed by Thomas Gleixner
Browse files

irqchip/omap-intc: Add support for spurious irq handling 



Under some conditions, irq sorting procedure used by INTC can go wrong
resulting in a spurious irq getting reported.

If this condition is not handled, it results in endless stream of:

    unexpected IRQ trap at vector 00

messages from ack_bad_irq()

Handle the spurious interrupt condition in omap-intc driver to prevent this.

Measurements using kernel function profiler on AM335x EVM running at 720MHz
show that after this patch omap_intc_handle_irq() takes about 37.4us against
34us before this patch.

Signed-off-by: default avatarSekhar Nori <nsekhar@ti.com>
Acked-by: default avatarTony Lindgren <tony@atomide.com>
Cc: John Ogness <john.ogness@linutronix.de>
Cc: Felipe Balbi <balbi@ti.com>
Cc: Jason Cooper <jason@lakedaemon.net>
Cc: Marc Zyngier <marc.zyngier@arm.com>
Link: http://lkml.kernel.org/r/9c78a6db02ac55f7af7371b417b6e414d2c3095b.1450188128.git.nsekhar@ti.com


Cc: stable@vger.kernel.org
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
parent 1fd9a710

drivers/irqchip/irq-omap-intc.c

+26 −1
Original line number Original line Diff line number Diff line
@@ -47,6 +47,7 @@ 
#define INTC_ILR0		0x0100

#define INTC_ILR0		0x0100





#define ACTIVEIRQ_MASK		0x7f	/* omap2/3 active interrupt bits */

#define ACTIVEIRQ_MASK		0x7f	/* omap2/3 active interrupt bits */

#define SPURIOUSIRQ_MASK	(0x1ffffff << 7)

#define INTCPS_NR_ILR_REGS	128

#define INTCPS_NR_ILR_REGS	128

#define INTCPS_NR_MIR_REGS	4

#define INTCPS_NR_MIR_REGS	4
@@ -329,11 +330,35 @@ static int __init omap_init_irq(u32 base, struct device_node *node) 
static asmlinkage void __exception_irq_entry

static asmlinkage void __exception_irq_entry

omap_intc_handle_irq(struct pt_regs *regs)

omap_intc_handle_irq(struct pt_regs *regs)

{

{

	extern unsigned long irq_err_count;

	u32 irqnr;

	u32 irqnr;





	irqnr = intc_readl(INTC_SIR);

	irqnr = intc_readl(INTC_SIR);



	/*

	 * A spurious IRQ can result if interrupt that triggered the

	 * sorting is no longer active during the sorting (10 INTC

	 * functional clock cycles after interrupt assertion). Or a

	 * change in interrupt mask affected the result during sorting

	 * time. There is no special handling required except ignoring

	 * the SIR register value just read and retrying.

	 * See section 6.2.5 of AM335x TRM Literature Number: SPRUH73K

	 *

	 * Many a times, a spurious interrupt situation has been fixed

	 * by adding a flush for the posted write acking the IRQ in

	 * the device driver. Typically, this is going be the device

	 * driver whose interrupt was handled just before the spurious

	 * IRQ occurred. Pay attention to those device drivers if you

	 * run into hitting the spurious IRQ condition below.

	 */

	if (unlikely((irqnr & SPURIOUSIRQ_MASK) == SPURIOUSIRQ_MASK)) {

		pr_err_once("%s: spurious irq!\n", __func__);

		irq_err_count++;

		omap_ack_irq(NULL);

		return;

	}



	irqnr &= ACTIVEIRQ_MASK;

	irqnr &= ACTIVEIRQ_MASK;

	WARN_ONCE(!irqnr, "Spurious IRQ ?\n");

	handle_domain_irq(domain, irqnr, regs);

	handle_domain_irq(domain, irqnr, regs);

}

}