irqchip: mips-gic: Handle pending interrupts once in __gic_irq_dispatch()

When an interrupt occurs __gic_irq_dispatch() continuously reads local
and shared pending registers until all is serviced before
returning. The problem with that is that it could introduce a long
delay before returning if a piece of hardware keeps triggering while
in one of these loops.

To ensure fairness and priority doesn't get skewed a lot, read local
and shared pending registers once to service each pending IRQ once.
If another interupt triggers while servicing the current ones, then we
shall re-enter the handler after we return.

Signed-off-by: Qais Yousef <qais.yousef@imgtec.com>
Cc: Jason Cooper <jason@lakedaemon.net>
Cc: Andrew Bresticker <abrestic@chromium.org>
Cc: <linux-mips@linux-mips.org>
Link: http://lkml.kernel.org/r/1421668289-828-1-git-send-email-qais.yousef@imgtec.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

1 files changed, 26 insertions, 18 deletions

diff --git a/drivers/irqchip/irq-mips-gic.c b/drivers/irqchip/irq-mips-gic.c
index 2b0468e3df6a..f3f9873dfb68 100644
--- a/drivers/irqchip/irq-mips-gic.c
+++ b/drivers/irqchip/irq-mips-gic.c
@@ -234,9 +234,9 @@ int gic_get_c0_perfcount_int(void)
                                   GIC_LOCAL_TO_HWIRQ(GIC_LOCAL_INT_PERFCTR));
 }
 
-static unsigned int gic_get_int(void)
+static void gic_handle_shared_int(void)
 {
-        unsigned int i;
+        unsigned int i, intr, virq;
         unsigned long *pcpu_mask;
         unsigned long pending_reg, intrmask_reg;
         DECLARE_BITMAP(pending, GIC_MAX_INTRS);
@@ -258,7 +258,16 @@ static unsigned int gic_get_int(void)
         bitmap_and(pending, pending, intrmask, gic_shared_intrs);
         bitmap_and(pending, pending, pcpu_mask, gic_shared_intrs);
 
-        return find_first_bit(pending, gic_shared_intrs);
+        intr = find_first_bit(pending, gic_shared_intrs);
+        while (intr != gic_shared_intrs) {
+                virq = irq_linear_revmap(gic_irq_domain,
+                                         GIC_SHARED_TO_HWIRQ(intr));
+                do_IRQ(virq);
+
+                /* go to next pending bit */
+                bitmap_clear(pending, intr, 1);
+                intr = find_first_bit(pending, gic_shared_intrs);
+        }
 }
 
 static void gic_mask_irq(struct irq_data *d)
@@ -385,16 +394,26 @@ static struct irq_chip gic_edge_irq_controller = {
 #endif
 };
 
-static unsigned int gic_get_local_int(void)
+static void gic_handle_local_int(void)
 {
         unsigned long pending, masked;
+        unsigned int intr, virq;
 
         pending = gic_read(GIC_REG(VPE_LOCAL, GIC_VPE_PEND));
         masked = gic_read(GIC_REG(VPE_LOCAL, GIC_VPE_MASK));
 
         bitmap_and(&pending, &pending, &masked, GIC_NUM_LOCAL_INTRS);
 
-        return find_first_bit(&pending, GIC_NUM_LOCAL_INTRS);
+        intr = find_first_bit(&pending, GIC_NUM_LOCAL_INTRS);
+        while (intr != GIC_NUM_LOCAL_INTRS) {
+                virq = irq_linear_revmap(gic_irq_domain,
+                                         GIC_LOCAL_TO_HWIRQ(intr));
+                do_IRQ(virq);
+
+                /* go to next pending bit */
+                bitmap_clear(&pending, intr, 1);
+                intr = find_first_bit(&pending, GIC_NUM_LOCAL_INTRS);
+        }
 }
 
 static void gic_mask_local_irq(struct irq_data *d)
@@ -453,19 +472,8 @@ static struct irq_chip gic_all_vpes_local_irq_controller = {
 
 static void __gic_irq_dispatch(void)
 {
-        unsigned int intr, virq;
-
-        while ((intr = gic_get_local_int()) != GIC_NUM_LOCAL_INTRS) {
-                virq = irq_linear_revmap(gic_irq_domain,
-                                         GIC_LOCAL_TO_HWIRQ(intr));
-                do_IRQ(virq);
-        }
-
-        while ((intr = gic_get_int()) != gic_shared_intrs) {
-                virq = irq_linear_revmap(gic_irq_domain,
-                                         GIC_SHARED_TO_HWIRQ(intr));
-                do_IRQ(virq);
-        }
+        gic_handle_local_int();
+        gic_handle_shared_int();
 }
 
 static void gic_irq_dispatch(unsigned int irq, struct irq_desc *desc)