linux-kernel - [PATCH 3.12 011/182] ARM: OMAP2+: INTC: Acknowledge stuck active interrupts

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Message-Id: <5a3dd1ee8b3c1dc27b66ace638ebe1a0d306ea0e.1399973152.git.jslaby@suse.cz>
Date:	Tue, 13 May 2014 11:26:03 +0200
From:	Jiri Slaby <jslaby@...e.cz>
To:	stable@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org,
	Stefan Sørensen 
	<stefan.sorensen@...ctralink.com>,
	Tony Lindgren <tony@...mide.com>, Jiri Slaby <jslaby@...e.cz>
Subject: [PATCH 3.12 011/182] ARM: OMAP2+: INTC: Acknowledge stuck active interrupts

From: Stefan Sørensen <stefan.sorensen@...ctralink.com>

3.12-stable review patch.  If anyone has any objections, please let me know.

===============

commit 698b48532539484b012fb7c4176b959d32a17d00 upstream.

When an interrupt has become active on the INTC it will stay active
until it is acked, even if masked or de-asserted. The
INTC_PENDING_IRQn registers are however updated and since these are
used by omap_intc_handle_irq to determine which interrupt to handle,
it will never see the active interrupt. This will result in a storm of
useless interrupts that is only stopped when another higher priority
interrupt is asserted.

Fix by sending the INTC an acknowledge if we find no interrupts to
handle.

Signed-off-by: Stefan Sørensen <stefan.sorensen@...ctralink.com>
Signed-off-by: Tony Lindgren <tony@...mide.com>
Signed-off-by: Jiri Slaby <jslaby@...e.cz>
---
 arch/arm/mach-omap2/irq.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/arch/arm/mach-omap2/irq.c b/arch/arm/mach-omap2/irq.c
index e022a869bff2..6037a9a01ed5 100644
--- a/arch/arm/mach-omap2/irq.c
+++ b/arch/arm/mach-omap2/irq.c
@@ -222,6 +222,7 @@ void __init ti81xx_init_irq(void)
 static inline void omap_intc_handle_irq(void __iomem *base_addr, struct pt_regs *regs)
 {
 	u32 irqnr;
+	int handled_irq = 0;
 
 	do {
 		irqnr = readl_relaxed(base_addr + 0x98);
@@ -249,8 +250,15 @@ out:
 		if (irqnr) {
 			irqnr = irq_find_mapping(domain, irqnr);
 			handle_IRQ(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);
 }
 
 asmlinkage void __exception_irq_entry omap2_intc_handle_irq(struct pt_regs *regs)
-- 
1.9.3

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