[tip: irq/core] irqchip/loongson-eiointc: Skip handling if there is no pending interrupt

["tip-bot2 for Bibo Mao" <tip-bot2@linutronix.de>]

The following commit has been merged into the irq/core branch of tip:

Commit-ID:     3eece72ded7f67776731709702f3d1b9893b6a4f
Gitweb:        https://git.kernel.org/tip/3eece72ded7f67776731709702f3d1b9893b6a4f
Author:        Bibo Mao <maobibo@loongson.cn>
AuthorDate:    Tue, 30 Jan 2024 16:27:21 +08:00
Committer:     Thomas Gleixner <tglx@linutronix.de>
CommitterDate: Tue, 13 Feb 2024 10:53:14 +01:00

irqchip/loongson-eiointc: Skip handling if there is no pending interrupt

eiointc_irq_dispatch() iterates over the pending bit registers of the
interrupt controller and evaluates the result even if there is no interrupt
pending in a particular 64bit chunk.

Skip handling and especially the pointless write back for clearing the
non-pending bits if a chunk is empty.

[ tglx: Massaged changelog ]

Signed-off-by: Bibo Mao <maobibo@loongson.cn>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Huacai Chen <chenhuacai@loongson.cn>
Link: https://lore.kernel.org/r/20240130082722.2912576-3-maobibo@loongson.cn

---
 drivers/irqchip/irq-loongson-eiointc.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/irqchip/irq-loongson-eiointc.c b/drivers/irqchip/irq-loongson-eiointc.c
index 1623cd7..fad22e2 100644
--- a/drivers/irqchip/irq-loongson-eiointc.c
+++ b/drivers/irqchip/irq-loongson-eiointc.c
@@ -198,6 +198,12 @@ static void eiointc_irq_dispatch(struct irq_desc *desc)
 
 	for (i = 0; i < eiointc_priv[0]->vec_count / VEC_COUNT_PER_REG; i++) {
 		pending = iocsr_read64(EIOINTC_REG_ISR + (i << 3));
+
+		/* Skip handling if pending bitmap is zero */
+		if (!pending)
+			continue;
+
+		/* Clear the IRQs */
 		iocsr_write64(pending, EIOINTC_REG_ISR + (i << 3));
 		while (pending) {
 			int bit = __ffs(pending);