[PATCH 5/6] irqchip/mips-gic: Use separate vector for shared interrupts in EIC mode

[Matt Redfearn]

In EIC mode, the GIC can assert 64 distinct interrupt sources in the
CPU. Until now, the GIC has routed all interrupt sources to a single CPU
interrupt source. This is inefficient since we end up checking both local
and shared interrupt flag registers for both local and shared
interrupts. This introduces additional latency into the interrupt paths
which is easy to remove in EIC mode by making use of an additional
vector for shared interrupt sources.

Signed-off-by: Matt Redfearn <matt.redfearn@xxxxxxxx>
---

 drivers/irqchip/irq-mips-gic.c | 15 +++++++++++++--
 1 file changed, 13 insertions(+), 2 deletions(-)

diff --git a/drivers/irqchip/irq-mips-gic.c b/drivers/irqchip/irq-mips-gic.c
index ee391f42e97d..541eae9a491d 100644
--- a/drivers/irqchip/irq-mips-gic.c
+++ b/drivers/irqchip/irq-mips-gic.c
@@ -52,6 +52,7 @@ static DEFINE_SPINLOCK(gic_lock);
 static struct irq_domain *gic_irq_domain;
 static struct irq_domain *gic_ipi_domain;
 static int gic_shared_intrs;
+static unsigned int shared_cpu_pin;
 static unsigned int gic_cpu_pin;
 static unsigned int timer_cpu_pin;
 static struct irq_chip gic_level_irq_controller, gic_edge_irq_controller;
@@ -406,6 +407,11 @@ static void __gic_irq_dispatch(void)
 	gic_handle_shared_int(false);
 }
 
+static void __gic_irq_dispatch_shared(void)
+{
+	gic_handle_shared_int(false);
+}
+
 static void gic_irq_dispatch(struct irq_desc *desc)
 {
 	gic_handle_local_int(true);
@@ -422,7 +428,7 @@ static int gic_shared_irq_domain_map(struct irq_domain *d, unsigned int virq,
 	data = irq_get_irq_data(virq);
 
 	spin_lock_irqsave(&gic_lock, flags);
-	write_gic_map_pin(intr, GIC_MAP_PIN_MAP_TO_PIN | gic_cpu_pin);
+	write_gic_map_pin(intr, GIC_MAP_PIN_MAP_TO_PIN | shared_cpu_pin);
 	write_gic_map_vp(intr, BIT(mips_cm_vp_id(cpu)));
 	gic_clear_pcpu_masks(intr);
 	set_bit(intr, per_cpu_ptr(pcpu_masks, cpu));
@@ -734,8 +740,13 @@ static int __init gic_of_init(struct device_node *node,
 		timer_cpu_pin = gic_cpu_pin;
 		set_vi_handler(gic_cpu_pin + GIC_PIN_TO_VEC_OFFSET,
 			       __gic_irq_dispatch);
+
+		/* Route all shared interrupts to pin 1, vector 2 */
+		shared_cpu_pin = 1;
+		set_vi_handler(shared_cpu_pin + GIC_PIN_TO_VEC_OFFSET,
+			       __gic_irq_dispatch_shared);
 	} else {
-		gic_cpu_pin = cpu_vec - GIC_CPU_PIN_OFFSET;
+		shared_cpu_pin = gic_cpu_pin = cpu_vec - GIC_CPU_PIN_OFFSET;
 		irq_set_chained_handler(MIPS_CPU_IRQ_BASE + cpu_vec,
 					gic_irq_dispatch);
 		/*
-- 
2.7.4