genirq: Allow irq chips to mark themself oneshot safe

Some interrupt chips like MSI are oneshot safe by implementation. For those interrupts we can avoid the mask/unmask sequence for threaded interrupt handlers. Signed-off-by: Thomas Gleixner <[email protected]> Link: http://lkml.kernel.org/r/alpine.LFD.2.02.1207132056540.32033@ionos Cc: Linus Torvalds <[email protected]> Cc: Avi Kivity <[email protected]> Cc: Marcelo Tosatti <[email protected]> Cc: Jan Kiszka <[email protected]>
jadonk · Jul 25, 2012 · dc9b229 · dc9b229
1 parent e2b34e3
commit dc9b229
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Showing 2 changed files with 15 additions and 1 deletion.
diff --git a/include/linux/irq.h b/include/linux/irq.h
@@ -349,6 +349,7 @@ enum {
 	IRQCHIP_MASK_ON_SUSPEND		= (1 <<  2),
 	IRQCHIP_ONOFFLINE_ENABLED	= (1 <<  3),
 	IRQCHIP_SKIP_SET_WAKE		= (1 <<  4),
+	IRQCHIP_ONESHOT_SAFE		= (1 <<  5),
 };
 
 /* This include will go away once we isolated irq_desc usage to core code */

diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c
@@ -959,6 +959,18 @@ __setup_irq(unsigned int irq, struct irq_desc *desc, struct irqaction *new)
 		goto out_thread;
 	}
 
+	/*
+	 * Drivers are often written to work w/o knowledge about the
+	 * underlying irq chip implementation, so a request for a
+	 * threaded irq without a primary hard irq context handler
+	 * requires the ONESHOT flag to be set. Some irq chips like
+	 * MSI based interrupts are per se one shot safe. Check the
+	 * chip flags, so we can avoid the unmask dance at the end of
+	 * the threaded handler for those.
+	 */
+	if (desc->irq_data.chip->flags & IRQCHIP_ONESHOT_SAFE)
+		new->flags &= ~IRQF_ONESHOT;
+
 	/*
 	 * The following block of code has to be executed atomically
 	 */
@@ -1033,7 +1045,8 @@ __setup_irq(unsigned int irq, struct irq_desc *desc, struct irqaction *new)
 		 */
 		new->thread_mask = 1 << ffz(thread_mask);
 
-	} else if (new->handler == irq_default_primary_handler) {
+	} else if (new->handler == irq_default_primary_handler &&
+		   !(desc->irq_data.chip->flags & IRQCHIP_ONESHOT_SAFE)) {
 		/*
 		 * The interrupt was requested with handler = NULL, so
 		 * we use the default primary handler for it. But it