genirq/chip: Change irq_chip_pm_put() return type to void

The irq_chip_pm_put() return value is only used in __irq_do_set_handler()
to trigger a WARN_ON() if it is negative, but doing so is not useful
because irq_chip_pm_put() simply passes the pm_runtime_put() return value
to its callers.

Returning an error code from pm_runtime_put() merely means that it has
not queued up a work item to check whether or not the device can be
suspended and there are many perfectly valid situations in which that
can happen, like after writing "on" to the devices' runtime PM "control"
attribute in sysfs for one example.

For this reason, modify irq_chip_pm_put() to discard the pm_runtime_put()
return value, change its return type to void, and drop the WARN_ON()
around the irq_chip_pm_put() invocation from __irq_do_set_handler().
Also update the irq_chip_pm_put() kerneldoc comment to be more accurate.

This will facilitate a planned change of the pm_runtime_put() return
type to void in the future.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: Thomas Gleixner <tglx@kernel.org>
Link: https://patch.msgid.link/5075294.31r3eYUQgx@rafael.j.wysocki

Author: rafaeljw

include/linux/irq.h

@@ -658,7 +658,7 @@ extern void handle_fasteoi_nmi(struct irq_desc *desc);
 
 extern int irq_chip_compose_msi_msg(struct irq_data *data, struct msi_msg *msg);
 extern int irq_chip_pm_get(struct irq_data *data);
-extern int irq_chip_pm_put(struct irq_data *data);
+extern void irq_chip_pm_put(struct irq_data *data);
 #ifdef	CONFIG_IRQ_DOMAIN_HIERARCHY
 extern void handle_fasteoi_ack_irq(struct irq_desc *desc);
 extern void handle_fasteoi_mask_irq(struct irq_desc *desc);

kernel/irq/chip.c

@@ -974,7 +974,7 @@ __irq_do_set_handler(struct irq_desc *desc, irq_flow_handler_t handle,
 		irq_state_set_disabled(desc);
 		if (is_chained) {
 			desc->action = NULL;
-			WARN_ON(irq_chip_pm_put(irq_desc_get_irq_data(desc)));
+			irq_chip_pm_put(irq_desc_get_irq_data(desc));
 		}
 		desc->depth = 1;
 	}
@@ -1530,20 +1530,20 @@ int irq_chip_pm_get(struct irq_data *data)
 }
 
 /**
- * irq_chip_pm_put - Disable power for an IRQ chip
+ * irq_chip_pm_put - Drop a PM reference on an IRQ chip
  * @data:	Pointer to interrupt specific data
  *
- * Disable the power to the IRQ chip referenced by the interrupt data
- * structure, belongs. Note that power will only be disabled, once this
- * function has been called for all IRQs that have called irq_chip_pm_get().
+ * Drop a power management reference, acquired via irq_chip_pm_get(), on the IRQ
+ * chip represented by the interrupt data structure.
+ *
+ * Note that this will not disable power to the IRQ chip until this function
+ * has been called for all IRQs that have called irq_chip_pm_get() and it may
+ * not disable power at all (if user space prevents that, for example).
  */
-int irq_chip_pm_put(struct irq_data *data)
+void irq_chip_pm_put(struct irq_data *data)
 {
 	struct device *dev = irq_get_pm_device(data);
-	int retval = 0;
-
-	if (IS_ENABLED(CONFIG_PM) && dev)
-		retval = pm_runtime_put(dev);
 
-	return (retval < 0) ? retval : 0;
+	if (dev)
+		pm_runtime_put(dev);
 }