ARCv2: MCIP: Use IDU_M_DISTRI_DEST mode if there is only 1 destination core

ARC linux uses 2 distribution modes for common interrupts: round robin
mode (IDU_M_DISTRI_RR) and a simple destination mode (IDU_M_DISTRI_DEST).
The first one is used when more than 1 cores may handle a common interrupt
and the second one is used when only 1 core may handle a common interrupt.

However idu_irq_set_affinity() always sets IDU_M_DISTRI_RR for all affinity
values. But there is no sense in setting of such mode if only 1 core must
handle a common interrupt.

Signed-off-by: Yuriy Kolerov <yuriy.kolerov@synopsys.com>
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>

1 files changed, 11 insertions, 2 deletions

diff --git a/arch/arc/kernel/mcip.c b/arch/arc/kernel/mcip.c
index 6d18bb871926..f39142acc89e 100644
--- a/arch/arc/kernel/mcip.c
+++ b/arch/arc/kernel/mcip.c
@@ -181,6 +181,8 @@ idu_irq_set_affinity(struct irq_data *data, const struct cpumask *cpumask,
 {
         unsigned long flags;
         cpumask_t online;
+        unsigned int destination_bits;
+        unsigned int distribution_mode;
 
         /* errout if no online cpu per @cpumask */
         if (!cpumask_and(&online, cpumask, cpu_online_mask))
@@ -188,8 +190,15 @@ idu_irq_set_affinity(struct irq_data *data, const struct cpumask *cpumask,
 
         raw_spin_lock_irqsave(&mcip_lock, flags);
 
-        idu_set_dest(data->hwirq, cpumask_bits(&online)[0]);
-        idu_set_mode(data->hwirq, IDU_M_TRIG_LEVEL, IDU_M_DISTRI_RR);
+        destination_bits = cpumask_bits(&online)[0];
+        idu_set_dest(data->hwirq, destination_bits);
+
+        if (ffs(destination_bits) == fls(destination_bits))
+                distribution_mode = IDU_M_DISTRI_DEST;
+        else
+                distribution_mode = IDU_M_DISTRI_RR;
+
+        idu_set_mode(data->hwirq, IDU_M_TRIG_LEVEL, distribution_mode);
 
         raw_spin_unlock_irqrestore(&mcip_lock, flags);