[added,to,the,3.18,stable,tree] irqchip/omap-intc: Add support for spurious irq handling

Message ID 1460887352-20128-7-git-send-email-sasha.levin@oracle.com
State New
Headers show

Commit Message

Sasha Levin April 17, 2016, 9:59 a.m.
From: Sekhar Nori <nsekhar@ti.com>

This patch has been added to the 3.18 stable tree. If you have any
objections, please let us know.


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[ Upstream commit d3b421cd07e4c0d4d6c0bbd55ca169c054fc081d ]

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>
Signed-off-by: Sasha Levin <sasha.levin@oracle.com>
 drivers/irqchip/irq-omap-intc.c | 27 ++++++++++++++++++++++++++-
 1 file changed, 26 insertions(+), 1 deletion(-)

diff --git a/drivers/irqchip/irq-omap-intc.c b/drivers/irqchip/irq-omap-intc.c
index e37490d..0ee0546 100644
--- a/drivers/irqchip/irq-omap-intc.c
+++ b/drivers/irqchip/irq-omap-intc.c
@@ -48,6 +48,7 @@ 
 #define INTC_ILR0		0x0100
 #define ACTIVEIRQ_MASK		0x7f	/* omap2/3 active interrupt bits */
+#define SPURIOUSIRQ_MASK	(0x1ffffff << 7)
 #define INTCPS_NR_ILR_REGS	128
@@ -331,11 +332,35 @@  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+	 * sorting is no longer active during the sorting (10 INTC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);