genirq: Prevent spurious detection for unconditionally polled interrupts

On a 68k platform a couple of interrupts are demultiplexed and
"polled" from a top level interrupt. Unfortunately there is no way to
determine which of the sub interrupts raised the top level interrupt,
so all of the demultiplexed interrupt handlers need to be
invoked. Given a high enough frequency this can trigger the spurious
interrupt detection mechanism, if one of the demultiplex interrupts
returns IRQ_NONE continuously. But this is a false positive as the
polling causes this behaviour and not buggy hardware/software.

Introduce IRQ_POLLED which can be set at interrupt chip setup time via
irq_set_status_flags(). The flag excludes the interrupt from the
spurious detector and from all core polling activities.

Reported-and-tested-by: Michael Schmitz <schmitzmic@gmail.com>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: linux-m68k@vger.kernel.org
Link: http://lkml.kernel.org/r/alpine.DEB.2.02.1311061149250.23353@ionos.tec.linutronix.de

1 files changed, 6 insertions, 1 deletions

diff --git a/include/linux/irq.h b/include/linux/irq.h
index 56bb0dc8b7d4..7dc10036eff5 100644
--- a/include/linux/irq.h
+++ b/include/linux/irq.h
@@ -70,6 +70,9 @@ typedef	void (*irq_preflow_handler_t)(struct irq_data *data);
  * IRQ_MOVE_PCNTXT              - Interrupt can be migrated from process context
  * IRQ_NESTED_TRHEAD            - Interrupt nests into another thread
  * IRQ_PER_CPU_DEVID            - Dev_id is a per-cpu variable
+ * IRQ_IS_POLLED                - Always polled by another interrupt. Exclude
+ *                                it from the spurious interrupt detection
+ *                                mechanism and from core side polling.
  */
 enum {
         IRQ_TYPE_NONE           = 0x00000000,
@@ -94,12 +97,14 @@ enum {
         IRQ_NESTED_THREAD       = (1 << 15),
         IRQ_NOTHREAD            = (1 << 16),
         IRQ_PER_CPU_DEVID       = (1 << 17),
+        IRQ_IS_POLLED           = (1 << 18),
 };
 
 #define IRQF_MODIFY_MASK        \
         (IRQ_TYPE_SENSE_MASK | IRQ_NOPROBE | IRQ_NOREQUEST | \
          IRQ_NOAUTOEN | IRQ_MOVE_PCNTXT | IRQ_LEVEL | IRQ_NO_BALANCING | \
-         IRQ_PER_CPU | IRQ_NESTED_THREAD | IRQ_NOTHREAD | IRQ_PER_CPU_DEVID)
+         IRQ_PER_CPU | IRQ_NESTED_THREAD | IRQ_NOTHREAD | IRQ_PER_CPU_DEVID | \
+         IRQ_IS_POLLED)
 
 #define IRQ_NO_BALANCING_MASK   (IRQ_PER_CPU | IRQ_NO_BALANCING)