genirq: Allow the irqchip state of an IRQ to be save/restored

There is a number of cases where a kernel subsystem may want to
introspect the state of an interrupt at the irqchip level:

- When a peripheral is shared between virtual machines,
  its interrupt state becomes part of the guest's state,
  and must be switched accordingly. KVM on arm/arm64 requires
  this for its guest-visible timer
- Some GPIO controllers seem to require peeking into the
  interrupt controller they are connected to to report
  their internal state

This seem to be a pattern that is common enough for the core code
to try and support this without too many horrible hacks. Introduce
a pair of accessors (irq_get_irqchip_state/irq_set_irqchip_state)
to retrieve the bits that can be of interest to another subsystem:
pending, active, and masked.

- irq_get_irqchip_state returns the state of the interrupt according
  to a parameter set to IRQCHIP_STATE_PENDING, IRQCHIP_STATE_ACTIVE,
  IRQCHIP_STATE_MASKED or IRQCHIP_STATE_LINE_LEVEL.
- irq_set_irqchip_state similarly sets the state of the interrupt.

Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Reviewed-by: Bjorn Andersson <bjorn.andersson@sonymobile.com>
Tested-by: Bjorn Andersson <bjorn.andersson@sonymobile.com>
Cc: linux-arm-kernel@lists.infradead.org
Cc: Abhijeet Dharmapurikar <adharmap@codeaurora.org>
Cc: Stephen Boyd <sboyd@codeaurora.org>
Cc: Phong Vo <pvo@apm.com>
Cc: Linus Walleij <linus.walleij@linaro.org>
Cc: Tin Huynh <tnhuynh@apm.com>
Cc: Y Vo <yvo@apm.com>
Cc: Toan Le <toanle@apm.com>
Cc: Bjorn Andersson <bjorn@kryo.se>
Cc: Jason Cooper <jason@lakedaemon.net>
Cc: Arnd Bergmann <arnd@arndb.de>
Link: http://lkml.kernel.org/r/1426676484-21812-2-git-send-email-marc.zyngier@arm.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

1 files changed, 14 insertions, 0 deletions

diff --git a/include/linux/interrupt.h b/include/linux/interrupt.h
index 150dde04cf4f..950ae4501826 100644
--- a/include/linux/interrupt.h
+++ b/include/linux/interrupt.h
@@ -361,6 +361,20 @@ static inline int disable_irq_wake(unsigned int irq)
         return irq_set_irq_wake(irq, 0);
 }
 
+/*
+ * irq_get_irqchip_state/irq_set_irqchip_state specific flags
+ */
+enum irqchip_irq_state {
+        IRQCHIP_STATE_PENDING,          /* Is interrupt pending? */
+        IRQCHIP_STATE_ACTIVE,           /* Is interrupt in progress? */
+        IRQCHIP_STATE_MASKED,           /* Is interrupt masked? */
+        IRQCHIP_STATE_LINE_LEVEL,       /* Is IRQ line high? */
+};
+
+extern int irq_get_irqchip_state(unsigned int irq, enum irqchip_irq_state which,
+                                 bool *state);
+extern int irq_set_irqchip_state(unsigned int irq, enum irqchip_irq_state which,
+                                 bool state);
 
 #ifdef CONFIG_IRQ_FORCED_THREADING
 extern bool force_irqthreads;