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

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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: Sekhar Nori <nsekhar@ti.com>
Acked-by: Tony 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: Thomas Gleixner <tglx@linutronix.de>
This commit is contained in:
Sekhar Nori 2015-12-15 19:56:12 +05:30 committed by Thomas Gleixner
parent 1fd9a71076
commit d3b421cd07
1 changed files with 26 additions and 1 deletions
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27
drivers/irqchip/irq-omap-intc.c
View file

@ -47,6 +47,7 @@
#define INTC_ILR0 0x0100
#define ACTIVEIRQ_MASK 0x7f /* omap2/3 active interrupt bits */
#define SPURIOUSIRQ_MASK (0x1ffffff << 7)
#define INTCPS_NR_ILR_REGS 128
#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
omap_intc_handle_irq(struct pt_regs *regs)
{
extern unsigned long irq_err_count;
u32 irqnr;
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* sorting is no longer active during the sorting (10 INTC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;
WARN_ONCE(!irqnr, "Spurious IRQ ?\n");
handle_domain_irq(domain, irqnr, regs);
}