linux-kernel - [RFC PATCH v2 2/2] genirq: Avoid unnecessary low level irq function calls

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Date:   Mon, 26 Jun 2017 19:33:34 +0800
From:   Jeffy Chen <jeffy.chen@...k-chips.com>
To:     linux-kernel@...r.kernel.org, tglx@...utronix.de
Cc:     briannorris@...omium.org, dianders@...omium.org,
        tfiga@...omium.org, Jeffy Chen <jeffy.chen@...k-chips.com>
Subject: [RFC PATCH v2 2/2] genirq: Avoid unnecessary low level irq function calls

Check irq state in enable/disable/unmask/mask_irq to avoid unnecessary
low level irq function calls.

Suggested-by: Thomas Gleixner <tglx@...utronix.de>
Signed-off-by: Jeffy Chen <jeffy.chen@...k-chips.com>
---

Changes in v2:
Remove unnecessary started state check.

 kernel/irq/chip.c | 53 +++++++++++++++++++++++++++++++++--------------------
 1 file changed, 33 insertions(+), 20 deletions(-)

diff --git a/kernel/irq/chip.c b/kernel/irq/chip.c
index 8a5b597..7e8a35c 100644
--- a/kernel/irq/chip.c
+++ b/kernel/irq/chip.c
@@ -247,22 +247,32 @@ void irq_shutdown(struct irq_desc *desc)
 
 void irq_enable(struct irq_desc *desc)
 {
-	irq_state_clr_disabled(desc);
-	if (desc->irq_data.chip->irq_enable)
-		desc->irq_data.chip->irq_enable(&desc->irq_data);
-	else
-		desc->irq_data.chip->irq_unmask(&desc->irq_data);
-	irq_state_clr_masked(desc);
+	if (!irqd_irq_disabled(&desc->irq_data)) {
+		unmask_irq(desc);
+	} else {
+		irq_state_clr_disabled(desc);
+		if (desc->irq_data.chip->irq_enable) {
+			desc->irq_data.chip->irq_enable(&desc->irq_data);
+			irq_state_clr_masked(desc);
+		} else {
+			unmask_irq(desc);
+		}
+	}
 }
 
 static void __irq_disable(struct irq_desc *desc, bool mask)
 {
-	irq_state_set_disabled(desc);
-	if (desc->irq_data.chip->irq_disable) {
-		desc->irq_data.chip->irq_disable(&desc->irq_data);
-		irq_state_set_masked(desc);
-	} else if (mask) {
-		mask_irq(desc);
+	if (irqd_irq_disabled(&desc->irq_data)) {
+		if (mask)
+			mask_irq(desc);
+	} else {
+		irq_state_set_disabled(desc);
+		if (desc->irq_data.chip->irq_disable) {
+			desc->irq_data.chip->irq_disable(&desc->irq_data);
+			irq_state_set_masked(desc);
+		} else if (mask) {
+			mask_irq(desc);
+		}
 	}
 }
 
@@ -311,18 +321,21 @@ void irq_percpu_disable(struct irq_desc *desc, unsigned int cpu)
 
 static inline void mask_ack_irq(struct irq_desc *desc)
 {
-	if (desc->irq_data.chip->irq_mask_ack)
+	if (desc->irq_data.chip->irq_mask_ack) {
 		desc->irq_data.chip->irq_mask_ack(&desc->irq_data);
-	else {
-		desc->irq_data.chip->irq_mask(&desc->irq_data);
+		irq_state_set_masked(desc);
+	} else {
+		mask_irq(desc);
 		if (desc->irq_data.chip->irq_ack)
 			desc->irq_data.chip->irq_ack(&desc->irq_data);
 	}
-	irq_state_set_masked(desc);
 }
 
 void mask_irq(struct irq_desc *desc)
 {
+	if (irqd_irq_masked(&desc->irq_data))
+		return;
+
 	if (desc->irq_data.chip->irq_mask) {
 		desc->irq_data.chip->irq_mask(&desc->irq_data);
 		irq_state_set_masked(desc);
@@ -331,6 +344,9 @@ void mask_irq(struct irq_desc *desc)
 
 void unmask_irq(struct irq_desc *desc)
 {
+	if (!irqd_irq_masked(&desc->irq_data))
+		return;
+
 	if (desc->irq_data.chip->irq_unmask) {
 		desc->irq_data.chip->irq_unmask(&desc->irq_data);
 		irq_state_clr_masked(desc);
@@ -344,10 +360,7 @@ void unmask_threaded_irq(struct irq_desc *desc)
 	if (chip->flags & IRQCHIP_EOI_THREADED)
 		chip->irq_eoi(&desc->irq_data);
 
-	if (chip->irq_unmask) {
-		chip->irq_unmask(&desc->irq_data);
-		irq_state_clr_masked(desc);
-	}
+	unmask_irq(desc);
 }
 
 /*
-- 
2.1.4