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.
Signed-off-by: Sekhar Nori <nsekhar@xxxxxx>
---
v2: increment error irq counter, use pr_err_once,
add a comment on tips to debug spurious irq
condition.
This patch results in a checkpatch warning about
extern definition of irq_err_count, but looks like
thats the prevalent method of accessing that counter.
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 8587d0f8d8c0..639708de5529 100644
--- a/drivers/irqchip/irq-omap-intc.c
+++ b/drivers/irqchip/irq-omap-intc.c
@@ -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
@@ -330,11 +331,35 @@ 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+ * sorting is no longer active during the sorting (10 INTC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 ((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);
}
--
2.6.3
--
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