From: Sekhar Nori <nsekhar@xxxxxx>
This patch has been added to the 3.18 stable tree. If you have any
objections, please let us know.
===============
[ 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@xxxxxx>
Acked-by: Tony Lindgren <tony@xxxxxxxxxxx>
Cc: John Ogness <john.ogness@xxxxxxxxxxxxx>
Cc: Felipe Balbi <balbi@xxxxxx>
Cc: Jason Cooper <jason@xxxxxxxxxxxxxx>
Cc: Marc Zyngier <marc.zyngier@xxxxxxx>
Link: http://lkml.kernel.org/r/9c78a6db02ac55f7af7371b417b6e414d2c3095b.1450188128.git.nsekhar@xxxxxx
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sasha.levin@xxxxxxxxxx>
---
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
#define INTCPS_NR_MIR_REGS 4
@@ -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+ * sorting is no longer active during the sorting (10 INTC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);
}
--
2.5.0
--
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