[PATCH 0/2] MIPS: SGI-IP27: micro-optimize arch_init_irq()

[PATCH 0/2] MIPS: SGI-IP27: micro-optimize arch_init_irq()

[Yury Norov]

A couple of cleanups for arch_init_irq()

This is a follow-up for [1].

Here:
 - drop unused 'i' variable, as reported by kernel robot [2];
 - fix typos in commit message;
 - add 2nd patch to handle WARN_ON() better.


[1] https://lore.kernel.org/lkml/20240413184913.69268-1-yury.norov@gmail.com/
[2] https://lore.kernel.org/oe-kbuild-all/202404161933.izfqZ32k-lkp@intel.com/

Yury Norov (2):
  MIPS: SGI-IP27: micro-optimize arch_init_irq()
  MIPS: SGI-IP27: use WARN_ON() output

 arch/mips/sgi-ip27/ip27-irq.c | 15 +++++----------
 1 file changed, 5 insertions(+), 10 deletions(-)

-- 
2.40.1

[PATCH v2 1/2] MIPS: SGI-IP27: micro-optimize arch_init_irq()

[Yury Norov]

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@gmail.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

[PATCH 2/2] MIPS: SGI-IP27: use WARN_ON() output

[Yury Norov]

WARN_ON() propagates the result of conditional expression, and it can be
used to return early in the following expression in the arch_init_irq().

This is a no-op cleanup, except that compiler may optimize the error paths
better because WARN_ON() implies 'unlikely()'.

Signed-off-by: Yury Norov <yury.norov@gmail.com>
---
 arch/mips/sgi-ip27/ip27-irq.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/arch/mips/sgi-ip27/ip27-irq.c b/arch/mips/sgi-ip27/ip27-irq.c
index d8acdf0439d2..00e63e9ef61d 100644
--- a/arch/mips/sgi-ip27/ip27-irq.c
+++ b/arch/mips/sgi-ip27/ip27-irq.c
@@ -289,13 +289,12 @@ void __init arch_init_irq(void)
 	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);
-	if (!fn)
+	if (WARN_ON(fn == NULL))
 		return;
+
 	domain = irq_domain_create_linear(fn, IP27_HUB_IRQ_COUNT,
 					  &hub_domain_ops, NULL);
-	WARN_ON(domain == NULL);
-	if (!domain)
+	if (WARN_ON(domain == NULL))
 		return;
 
 	irq_set_default_host(domain);
-- 
2.40.1

Re: [PATCH v2 1/2] MIPS: SGI-IP27: micro-optimize arch_init_irq()

[Thomas Bogendoerfer]

On Tue, Apr 16, 2024 at 10:37:10AM -0700, Yury Norov wrote:
> 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@gmail.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;

I've already applied your first version, so I need an incremental
patch, which just removes the unused variable.

Thomas.

-- 
Crap can work. Given enough thrust pigs will fly, but it's not necessarily a
good idea.                                                [ RFC1925, 2.3 ]

Re: [PATCH v2 1/2] MIPS: SGI-IP27: micro-optimize arch_init_irq()

[Yury Norov]

On Wed, Apr 17, 2024 at 01:10:52PM +0200, Thomas Bogendoerfer wrote:
> On Tue, Apr 16, 2024 at 10:37:10AM -0700, Yury Norov wrote:
> > 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@gmail.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;
> 
> I've already applied your first version, so I need an incremental
> patch, which just removes the unused variable.

Sure, please find below.

From ce447fe69092c48bb59a6c4cb08ee5f9080f0ad6 Mon Sep 17 00:00:00 2001
From: Yury Norov <yury.norov@gmail.com>
Date: Mon, 22 Apr 2024 15:52:12 -0700
Subject: [PATCH] MIPS: SGI-IP27: fix -Wunused-variable in arch_init_irq()

Commit 40e20fbccfb722f21 (MIPS: SGI-IP27: micro-optimize arch_init_irq())
replaced a for-loop iteration with bitmap_set() calls, but didn't remove
an iteration variable.

Fixes: 40e20fbccfb722f21 (MIPS: SGI-IP27: micro-optimize arch_init_irq())
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202404161933.izfqZ32k-lkp@intel.com/
Signed-off-by: Yury Norov <yury.norov@gmail.com>
---
 arch/mips/sgi-ip27/ip27-irq.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/arch/mips/sgi-ip27/ip27-irq.c b/arch/mips/sgi-ip27/ip27-irq.c
index dcb14a234b1c..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();
 
-- 
2.40.1