genirq: Support per-IRQ thread disabling.

This adds support for disabling threading on a per-IRQ basis via the IRQ
status instead of the IRQ flow, which is necessary for interrupts that
don't follow the natural IRQ flow channels, such as those that are
virtually created.

The new APIs added are simply:

	irq_set_thread()
	irq_set_nothread()

which follow the rest of the IRQ status routines.

Chained handlers also have IRQ_NOTHREAD set on them automatically, making
the lack of threading explicit rather than implicit. Subsequently, the
nothread flag can be viewed through the standard genirq debugging
facilities.

[ tglx: Fixed cleanup fallout ]
Signed-off-by: Paul Mundt <lethal@linux-sh.org>
Link: http://lkml.kernel.org/r/%3C20110406210135.GF18426%40linux-sh.org%3ESigned-off-by: Thomas Gleixner <tglx@linutronix.de>

include/linux/irq.h

@@ -59,6 +59,7 @@ typedef	void (*irq_preflow_handler_t)(struct irq_data *data);
  * IRQ_NOPROBE			- Interrupt cannot be probed by autoprobing
  * IRQ_NOREQUEST		- Interrupt cannot be requested via
  *				  request_irq()
+ * IRQ_NOTHREAD			- Interrupt cannot be threaded
  * IRQ_NOAUTOEN			- Interrupt is not automatically enabled in
  *				  request/setup_irq()
  * IRQ_NO_BALANCING		- Interrupt cannot be balanced (affinity set)
@@ -85,6 +86,7 @@ enum {
 	IRQ_NO_BALANCING	= (1 << 13),
 	IRQ_MOVE_PCNTXT		= (1 << 14),
 	IRQ_NESTED_THREAD	= (1 << 15),
+	IRQ_NOTHREAD		= (1 << 16),
 };
 
 #define IRQF_MODIFY_MASK	\
@@ -422,7 +424,7 @@ irq_set_handler(unsigned int irq, irq_flow_handler_t handle)
 /*
  * Set a highlevel chained flow handler for a given IRQ.
  * (a chained handler is automatically enabled and set to
- *  IRQ_NOREQUEST and IRQ_NOPROBE)
+ *  IRQ_NOREQUEST, IRQ_NOPROBE, and IRQ_NOTHREAD)
  */
 static inline void
 irq_set_chained_handler(unsigned int irq, irq_flow_handler_t handle)
@@ -452,6 +454,16 @@ static inline void irq_set_probe(unsigned int irq)
 	irq_modify_status(irq, IRQ_NOPROBE, 0);
 }
 
+static inline void irq_set_nothread(unsigned int irq)
+{
+	irq_modify_status(irq, 0, IRQ_NOTHREAD);
+}
+
+static inline void irq_set_thread(unsigned int irq)
+{
+	irq_modify_status(irq, IRQ_NOTHREAD, 0);
+}
+
 static inline void irq_set_nested_thread(unsigned int irq, bool nest)
 {
 	if (nest)

kernel/irq/chip.c

@@ -573,6 +573,7 @@ __irq_set_handler(unsigned int irq, irq_flow_handler_t handle, int is_chained,
 	if (handle != handle_bad_irq && is_chained) {
 		irq_settings_set_noprobe(desc);
 		irq_settings_set_norequest(desc);
+		irq_settings_set_nothread(desc);
 		irq_startup(desc);
 	}
 out:

kernel/irq/debug.h

@@ -27,6 +27,7 @@ static inline void print_irq_desc(unsigned int irq, struct irq_desc *desc)
 	P(IRQ_PER_CPU);
 	P(IRQ_NOPROBE);
 	P(IRQ_NOREQUEST);
+	P(IRQ_NOTHREAD);
 	P(IRQ_NOAUTOEN);
 
 	PS(IRQS_AUTODETECT);

kernel/irq/manage.c

@@ -900,7 +900,8 @@ __setup_irq(unsigned int irq, struct irq_desc *desc, struct irqaction *new)
 		 */
 		new->handler = irq_nested_primary_handler;
 	} else {
-		irq_setup_forced_threading(new);
+		if (irq_settings_can_thread(desc))
+			irq_setup_forced_threading(new);
 	}
 
 	/*

kernel/irq/settings.h

@@ -8,6 +8,7 @@ enum {
 	_IRQ_LEVEL		= IRQ_LEVEL,
 	_IRQ_NOPROBE		= IRQ_NOPROBE,
 	_IRQ_NOREQUEST		= IRQ_NOREQUEST,
+	_IRQ_NOTHREAD		= IRQ_NOTHREAD,
 	_IRQ_NOAUTOEN		= IRQ_NOAUTOEN,
 	_IRQ_MOVE_PCNTXT	= IRQ_MOVE_PCNTXT,
 	_IRQ_NO_BALANCING	= IRQ_NO_BALANCING,
@@ -20,6 +21,7 @@ enum {
 #define IRQ_LEVEL		GOT_YOU_MORON
 #define IRQ_NOPROBE		GOT_YOU_MORON
 #define IRQ_NOREQUEST		GOT_YOU_MORON
+#define IRQ_NOTHREAD		GOT_YOU_MORON
 #define IRQ_NOAUTOEN		GOT_YOU_MORON
 #define IRQ_NESTED_THREAD	GOT_YOU_MORON
 #undef IRQF_MODIFY_MASK
@@ -94,6 +96,21 @@ static inline void irq_settings_set_norequest(struct irq_desc *desc)
 	desc->status_use_accessors |= _IRQ_NOREQUEST;
 }
 
+static inline bool irq_settings_can_thread(struct irq_desc *desc)
+{
+	return !(desc->status_use_accessors & _IRQ_NOTHREAD);
+}
+
+static inline void irq_settings_clr_nothread(struct irq_desc *desc)
+{
+	desc->status_use_accessors &= ~_IRQ_NOTHREAD;
+}
+
+static inline void irq_settings_set_nothread(struct irq_desc *desc)
+{
+	desc->status_use_accessors |= _IRQ_NOTHREAD;
+}
+
 static inline bool irq_settings_can_probe(struct irq_desc *desc)
 {
 	return !(desc->status_use_accessors & _IRQ_NOPROBE);