linux-kernel - Re: [PATCH] irqchip/irq-brcmstb-l2: Avoid saving mask on shutdown

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Message-ID: <87il09ufl4.ffs@tglx>
Date: Tue, 23 Apr 2024 01:45:27 +0200
From: Thomas Gleixner <tglx@...utronix.de>
To: Florian Fainelli <f.fainelli@...il.com>, Florian Fainelli
 <florian.fainelli@...adcom.com>, linux-kernel@...r.kernel.org
Cc: opendmb@...il.com, Tim Ross <tim.ross@...adcom.com>, Broadcom internal
 kernel review list <bcm-kernel-feedback-list@...adcom.com>, "open
 list:BROADCOM BMIPS MIPS ARCHITECTURE" <linux-mips@...r.kernel.org>,
 "moderated list:BROADCOM BCM7XXX ARM ARCHITECTURE"
 <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH] irqchip/irq-brcmstb-l2: Avoid saving mask on shutdown

On Mon, Apr 22 2024 at 15:26, Florian Fainelli wrote:
> On 4/22/24 14:29, Thomas Gleixner wrote:
>>> +	if (save)
>>> +		b->saved_mask = irq_reg_readl(gc, ct->regs.mask);
>> 
>> what's the conditional actually buying you except more complex code?
>
> Not much this is an optimization that is simple to carry out. There can 
> be dozens of such L2 interrupt controllers in a given system and the 
> MMIO accesses start adding up eventually.

I'm impressed by saving ~12 microseconds per one dozen of interrupt
controllers on system shutdown :)