soc/tegra: pmc: Add comments clarifying wake events

Add some comments to clarify the purpose of the wake event support
implemented in the PMC driver.
Reviewed-by: Jon Hunter <jonathanh@nvidia.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>

drivers/soc/tegra/pmc.c

@@ -241,6 +241,11 @@ struct tegra_pmc_soc {
 	const char * const *reset_levels;
 	unsigned int num_reset_levels;
 
+	/*
+	 * These describe events that can wake the system from sleep (i.e.
+	 * LP0 or SC7). Wakeup from other sleep states (such as LP1 or LP2)
+	 * are dealt with in the LIC.
+	 */
 	const struct tegra_wake_event *wake_events;
 	unsigned int num_wake_events;
 };
@@ -1906,6 +1911,11 @@ static int tegra_pmc_irq_alloc(struct irq_domain *domain, unsigned int virq,
 		}
 	}
 
+	/*
+	 * For interrupts that don't have associated wake events, assign a
+	 * dummy hardware IRQ number. This is used in the ->irq_set_type()
+	 * and ->irq_set_wake() callbacks to return early for these IRQs.
+	 */
 	if (i == soc->num_wake_events)
 		err = irq_domain_set_hwirq_and_chip(domain, virq, ULONG_MAX,
 						    &pmc->irq, pmc);
@@ -1924,6 +1934,7 @@ static int tegra_pmc_irq_set_wake(struct irq_data *data, unsigned int on)
 	unsigned int offset, bit;
 	u32 value;
 
+	/* nothing to do if there's no associated wake event */
 	if (WARN_ON(data->hwirq == ULONG_MAX))
 		return 0;
 
@@ -1954,6 +1965,7 @@ static int tegra_pmc_irq_set_type(struct irq_data *data, unsigned int type)
 	struct tegra_pmc *pmc = irq_data_get_irq_chip_data(data);
 	u32 value;
 
+	/* nothing to do if there's no associated wake event */
 	if (data->hwirq == ULONG_MAX)
 		return 0;