[PATCH] irqchip/sifive-plic: add irq_mask and irq_unmask

[Darius Rad <darius@bluespec.com>]

As per the existing comment, irq_mask and irq_unmask do not need
to do anything for the PLIC.  However, the functions must exist
(the pointers cannot be NULL) as they are not optional, based on
the documentation (Documentation/core-api/genericirq.rst) as well
as existing usage (e.g., include/linux/irqchip/chained_irq.h).

Signed-off-by: Darius Rad <darius@bluespec.com>
---
 drivers/irqchip/irq-sifive-plic.c | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/drivers/irqchip/irq-sifive-plic.c b/drivers/irqchip/irq-sifive-plic.c
index cf755964f2f8..52d5169f924f 100644
--- a/drivers/irqchip/irq-sifive-plic.c
+++ b/drivers/irqchip/irq-sifive-plic.c
@@ -111,6 +111,13 @@ static void plic_irq_disable(struct irq_data *d)
 	plic_irq_toggle(cpu_possible_mask, d->hwirq, 0);
 }
 
+/*
+ * There is no need to mask/unmask PLIC interrupts.  They are "masked"
+ * by reading claim and "unmasked" when writing it back.
+ */
+static void plic_irq_mask(struct irq_data *d) { }
+static void plic_irq_unmask(struct irq_data *d) { }
+
 #ifdef CONFIG_SMP
 static int plic_set_affinity(struct irq_data *d,
 			     const struct cpumask *mask_val, bool force)
@@ -138,12 +145,10 @@ static int plic_set_affinity(struct irq_data *d,
 
 static struct irq_chip plic_chip = {
 	.name		= "SiFive PLIC",
-	/*
-	 * There is no need to mask/unmask PLIC interrupts.  They are "masked"
-	 * by reading claim and "unmasked" when writing it back.
-	 */
 	.irq_enable	= plic_irq_enable,
 	.irq_disable	= plic_irq_disable,
+	.irq_mask	= plic_irq_mask,
+	.irq_unmask	= plic_irq_unmask,
 #ifdef CONFIG_SMP
 	.irq_set_affinity = plic_set_affinity,
 #endif
-- 
2.20.1