[3.13.y.z extended stable] Patch "ARM: OMAP2+: INTC: Acknowledge stuck active interrupts" has been added to staging queue

[Kamal Mostafa]

This is a note to let you know that I have just added a patch titled

    ARM: OMAP2+: INTC: Acknowledge stuck active interrupts

to the linux-3.13.y-queue branch of the 3.13.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.13.y-queue

This patch is scheduled to be released in version 3.13.11.1.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.13.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

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>From 5266a4b6045134cab869a637192953e13692b742 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Stefan=20S=C3=B8rensen?= <stefan.sorensen at spectralink.com>
Date: Thu, 6 Mar 2014 16:27:15 +0100
Subject: ARM: OMAP2+: INTC: Acknowledge stuck active interrupts
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

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 at spectralink.com>
Signed-off-by: Tony Lindgren <tony at atomide.com>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 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 e022a86..6037a9a 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)
--
1.9.1