Re: Fwd: [RFC] IRQ type flags

[Russell King <rmk+lkml@arm.linux.org.uk>]

Here's an updated patch, taking account of folks comments.  The changes
from the previous patch are:

* Move SA_TRIGGER into linux/signal.h
* Change SA_TRIGGER_* to match IORESOURCE_IRQ_* definitions
* Change ARM __IRQT_* definitions to match IORESOURCE_IRQ_* definitions
* Add a comment to explain the case where no SA_TRIGGER_* flags are
  passed to request_irq.

----
Some ARM platforms have the ability to program the interrupt controller to
detect various interrupt edges and/or levels.  For some platforms, this is
critical to setup correctly, particularly those which the setting is
dependent on the device.

Currently, ARM drivers do (eg) the following:

	err = request_irq(irq, ...);

	set_irq_type(irq, IRQT_RISING);

However, if the interrupt has previously been programmed to be level
sensitive (for whatever reason) then this will cause an interrupt storm.

Hence, if we combine set_irq_type() with request_irq(), we can then safely
set the type prior to unmasking the interrupt.  The unfortunate problem is
that in order to support this, these flags need to be visible outside of
the ARM architecture - drivers such as smc91x need these flags and they're
cross-architecture.

Finally, the SA_TRIGGER_* flag passed to request_irq() should reflect the
property that the device would like.  The IRQ controller code should do its
best to select the most appropriate supported mode.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
---

 arch/arm/kernel/irq.c  |   14 ++++++++++++--
 include/asm-arm/irq.h  |   12 ++++++++----
 include/linux/signal.h |   13 +++++++++++++
 3 files changed, 33 insertions(+), 6 deletions(-)

diff --git a/arch/arm/kernel/irq.c b/arch/arm/kernel/irq.c
--- a/arch/arm/kernel/irq.c
+++ b/arch/arm/kernel/irq.c
@@ -684,8 +684,12 @@ int setup_irq(unsigned int irq, struct i
 	spin_lock_irqsave(&irq_controller_lock, flags);
 	p = &desc->action;
 	if ((old = *p) != NULL) {
-		/* Can't share interrupts unless both agree to */
-		if (!(old->flags & new->flags & SA_SHIRQ)) {
+		/*
+		 * Can't share interrupts unless both agree to and are
+		 * the same type.
+		 */
+		if (!(old->flags & new->flags & SA_SHIRQ) ||
+		    (~old->flags & new->flags) & SA_TRIGGER_MASK) {
 			spin_unlock_irqrestore(&irq_controller_lock, flags);
 			return -EBUSY;
 		}
@@ -705,6 +709,12 @@ int setup_irq(unsigned int irq, struct i
 		desc->running = 0;
 		desc->pending = 0;
 		desc->disable_depth = 1;
+
+		if (new->flags & SA_TRIGGER_MASK) {
+			unsigned int type = new->flags & SA_TRIGGER;
+			desc->chip->set_type(irq, type);
+		}
+
 		if (!desc->noautoenable) {
 			desc->disable_depth = 0;
 			desc->chip->unmask(irq);
diff --git a/include/asm-arm/irq.h b/include/asm-arm/irq.h
--- a/include/asm-arm/irq.h
+++ b/include/asm-arm/irq.h
@@ -25,10 +25,14 @@ extern void disable_irq_nosync(unsigned 
 extern void disable_irq(unsigned int);
 extern void enable_irq(unsigned int);
 
-#define __IRQT_FALEDGE	(1 << 0)
-#define __IRQT_RISEDGE	(1 << 1)
-#define __IRQT_LOWLVL	(1 << 2)
-#define __IRQT_HIGHLVL	(1 << 3)
+/*
+ * These correspond with the SA_TRIGGER_* defines, and therefore the
+ * IRQRESOURCE_IRQ_* defines.
+ */
+#define __IRQT_RISEDGE	(1 << 0)
+#define __IRQT_FALEDGE	(1 << 1)
+#define __IRQT_HIGHLVL	(1 << 2)
+#define __IRQT_LOWLVL	(1 << 3)
 
 #define IRQT_NOEDGE	(0)
 #define IRQT_RISING	(__IRQT_RISEDGE)
diff --git a/include/linux/signal.h b/include/linux/signal.h
--- a/include/linux/signal.h
+++ b/include/linux/signal.h
@@ -18,6 +18,19 @@
 #define SA_PROBE		SA_ONESHOT
 #define SA_SAMPLE_RANDOM	SA_RESTART
 #define SA_SHIRQ		0x04000000
+/*
+ * As above, these correspond to the IORESOURCE_IRQ_* defines in
+ * linux/ioport.h to select the interrupt line behaviour.  When
+ * requesting an interrupt without specifying a SA_TRIGGER, the
+ * setting should be assumed to be "as already configured", which
+ * may be as per machine or firmware initialisation.
+ */
+#define SA_TRIGGER_LOW		0x00000008
+#define SA_TRIGGER_HIGH		0x00000004
+#define SA_TRIGGER_FALLING	0x00000002
+#define SA_TRIGGER_RISING	0x00000001
+#define SA_TRIGGER_MASK	(SA_TRIGGER_HIGH|SA_TRIGGER_LOW|\
+				 SA_TRIGGER_RISING|SA_TRIGGER_FALLING)
 
 /*
  * Real Time signals may be queued.

-- 
Russell King
 Linux kernel    2.6 ARM Linux   - http://www.arm.linux.org.uk/
 maintainer of:  2.6 Serial core
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