linux-kernel - [PATCH] irqchip/gicv3-its: skip irq affinity setting when target cpu is the same as current setting

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Date:   Thu, 18 May 2017 16:19:13 +0800
From:   Majun <majun258@...wei.com>
To:     <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>, <marc.zyngier@....com>,
        <tglx@...utronix.de>, <majun258@...wei.com>
Subject: [PATCH] irqchip/gicv3-its: skip irq affinity setting when target cpu is the same as current setting

From: MaJun <majun258@...wei.com>

Just skip the irq affinity setting when the target cpu is the same as
current setting.
This is a small optimization for irq affinity setting logic.

Signed-off-by: MaJun <majun258@...wei.com>
---
 drivers/irqchip/irq-gic-v3-its.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/drivers/irqchip/irq-gic-v3-its.c b/drivers/irqchip/irq-gic-v3-its.c
index 45ea1933..b335280 100644
--- a/drivers/irqchip/irq-gic-v3-its.c
+++ b/drivers/irqchip/irq-gic-v3-its.c
@@ -644,9 +644,12 @@ static int its_set_affinity(struct irq_data *d, const struct cpumask *mask_val,
 	if (cpu >= nr_cpu_ids)
 		return -EINVAL;
 
-	target_col = &its_dev->its->collections[cpu];
-	its_send_movi(its_dev, target_col, id);
-	its_dev->event_map.col_map[id] = cpu;
+	/* don't set the affinity when the target cpu is same as current one */
+	if (cpu != its_dev->event_map.col_map[id]) {
+		target_col = &its_dev->its->collections[cpu];
+		its_send_movi(its_dev, target_col, id);
+		its_dev->event_map.col_map[id] = cpu;
+	}
 
 	return IRQ_SET_MASK_OK_DONE;
 }
-- 
1.7.12.4