genirq: Add flag to force mask in disable_irq[_nosync]()

If an irq chip does not implement the irq_disable callback, then we
use a lazy approach for disabling the interrupt. That means that the
interrupt is marked disabled, but the interrupt line is not
immediately masked in the interrupt chip. It only becomes masked if
the interrupt is raised while it's marked disabled. We use this to avoid
possibly expensive mask/unmask operations for common case operations.

Unfortunately there are devices which do not allow the interrupt to be
disabled easily at the device level. They are forced to use
disable_irq_nosync(). This can result in taking each interrupt twice.

Instead of enforcing the non lazy mode on all interrupts of a irq
chip, provide a settings flag, which can be set by the driver for that
particular interrupt line.

Reported-and-tested-by: Duc Dang <dhdang@apm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Marc Zyngier <marc.zyngier@arm.com>
Cc: Jason Cooper <jason@lakedaemon.net>
Link: http://lkml.kernel.org/r/alpine.DEB.2.11.1510092348370.6097@nanos

3 files changed, 22 insertions, 0 deletions

diff --git a/kernel/irq/chip.c b/kernel/irq/chip.c
index 4aa00d325b8c..15206453b12a 100644
--- a/kernel/irq/chip.c
+++ b/kernel/irq/chip.c
@@ -241,6 +241,13 @@ void irq_enable(struct irq_desc *desc)
  * disabled. If an interrupt happens, then the interrupt flow
  * handler masks the line at the hardware level and marks it
  * pending.
+ *
+ * If the interrupt chip does not implement the irq_disable callback,
+ * a driver can disable the lazy approach for a particular irq line by
+ * calling 'irq_set_status_flags(irq, IRQ_DISABLE_UNLAZY)'. This can
+ * be used for devices which cannot disable the interrupt at the
+ * device level under certain circumstances and have to use
+ * disable_irq[_nosync] instead.
  */
 void irq_disable(struct irq_desc *desc)
 {
@@ -248,6 +255,8 @@ void irq_disable(struct irq_desc *desc)
         if (desc->irq_data.chip->irq_disable) {
                 desc->irq_data.chip->irq_disable(&desc->irq_data);
                 irq_state_set_masked(desc);
+        } else if (irq_settings_disable_unlazy(desc)) {
+                mask_irq(desc);
         }
 }
 
diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c
index 312f9cb12805..a71175ff98d5 100644
--- a/kernel/irq/manage.c
+++ b/kernel/irq/manage.c
@@ -1463,6 +1463,7 @@ static struct irqaction *__free_irq(unsigned int irq, void *dev_id)
 
         /* If this was the last handler, shut down the IRQ line: */
         if (!desc->action) {
+                irq_settings_clr_disable_unlazy(desc);
                 irq_shutdown(desc);
                 irq_release_resources(desc);
         }
diff --git a/kernel/irq/settings.h b/kernel/irq/settings.h
index 3320b84cc60f..320579d89091 100644
--- a/kernel/irq/settings.h
+++ b/kernel/irq/settings.h
@@ -15,6 +15,7 @@ enum {
         _IRQ_NESTED_THREAD      = IRQ_NESTED_THREAD,
         _IRQ_PER_CPU_DEVID      = IRQ_PER_CPU_DEVID,
         _IRQ_IS_POLLED          = IRQ_IS_POLLED,
+        _IRQ_DISABLE_UNLAZY     = IRQ_DISABLE_UNLAZY,
         _IRQF_MODIFY_MASK       = IRQF_MODIFY_MASK,
 };
 
@@ -28,6 +29,7 @@ enum {
 #define IRQ_NESTED_THREAD       GOT_YOU_MORON
 #define IRQ_PER_CPU_DEVID       GOT_YOU_MORON
 #define IRQ_IS_POLLED           GOT_YOU_MORON
+#define IRQ_DISABLE_UNLAZY      GOT_YOU_MORON
 #undef IRQF_MODIFY_MASK
 #define IRQF_MODIFY_MASK        GOT_YOU_MORON
 
@@ -154,3 +156,13 @@ static inline bool irq_settings_is_polled(struct irq_desc *desc)
 {
         return desc->status_use_accessors & _IRQ_IS_POLLED;
 }
+
+static inline bool irq_settings_disable_unlazy(struct irq_desc *desc)
+{
+        return desc->status_use_accessors & _IRQ_DISABLE_UNLAZY;
+}
+
+static inline void irq_settings_clr_disable_unlazy(struct irq_desc *desc)
+{
+        desc->status_use_accessors &= ~_IRQ_DISABLE_UNLAZY;
+}