linux-kernel - [PATCH v2 1/2] MIPS: SGI-IP27: micro-optimize arch_init

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Date: Tue, 16 Apr 2024 10:37:10 -0700
From: Yury Norov <yury.norov@...il.com>
To: Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
	Florian Fainelli <f.fainelli@...il.com>,
	linux-mips@...r.kernel.org,
	linux-kernel@...r.kernel.org
Cc: Yury Norov <yury.norov@...il.com>
Subject: [PATCH v2 1/2] MIPS: SGI-IP27: micro-optimize arch_init_irq()

The function sets adjusted groups of bits in hub_irq_map by using
for-loops. There's a bitmap_set() function dedicated to do this.

Because [0, CPU_CALL_B_IRQ] and [NI_BRDCAST_ERR_A, MSC_PANIC_INTR]
ranges belong to the same machine word, bitmap_set() would boil down
to an inline wrapper in both cases, avoiding generating a loop, with
the associate overhead. Effectively, it would be a compile-time:

	*hub_irq_map = GENMASK() | GENMASK();

Signed-off-by: Yury Norov <yury.norov@...il.com>
---
 arch/mips/sgi-ip27/ip27-irq.c | 8 ++------
 1 file changed, 2 insertions(+), 6 deletions(-)

diff --git a/arch/mips/sgi-ip27/ip27-irq.c b/arch/mips/sgi-ip27/ip27-irq.c
index 8f5299b269e7..d8acdf0439d2 100644
--- a/arch/mips/sgi-ip27/ip27-irq.c
+++ b/arch/mips/sgi-ip27/ip27-irq.c
@@ -277,7 +277,6 @@ void __init arch_init_irq(void)
 {
 	struct irq_domain *domain;
 	struct fwnode_handle *fn;
-	int i;
 
 	mips_cpu_irq_init();
 
@@ -286,11 +285,8 @@ void __init arch_init_irq(void)
 	 * Mark these as reserved right away so they won't be used accidentally
 	 * later.
 	 */
-	for (i = 0; i <= CPU_CALL_B_IRQ; i++)
-		set_bit(i, hub_irq_map);
-
-	for (i = NI_BRDCAST_ERR_A; i <= MSC_PANIC_INTR; i++)
-		set_bit(i, hub_irq_map);
+	bitmap_set(hub_irq_map, 0, CPU_CALL_B_IRQ + 1);
+	bitmap_set(hub_irq_map, NI_BRDCAST_ERR_A, MSC_PANIC_INTR - NI_BRDCAST_ERR_A + 1);
 
 	fn = irq_domain_alloc_named_fwnode("HUB");
 	WARN_ON(fn == NULL);
-- 
2.40.1