linux-kernel - Re: [PATCH] irqchip/apple-aic: Only handle PMC interrupt as FIQ when configured to fire FIQ

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Message-Id: <aef452c6-1e12-4510-8fb9-1dc597cf69bf@app.fastmail.com>
Date: Sat, 18 Jan 2025 13:24:47 +0100
From: "Sven Peter" <sven@...npeter.dev>
To: "Nick Chan" <towinchenmi@...il.com>, "Hector Martin" <marcan@...can.st>,
 "Alyssa Rosenzweig" <alyssa@...enzweig.io>,
 "Thomas Gleixner" <tglx@...utronix.de>, "Marc Zyngier" <maz@...nel.org>,
 asahi@...ts.linux.dev, linux-arm-kernel@...ts.infradead.org,
 linux-kernel@...r.kernel.org
Cc: stable@...r.kernel.org
Subject: Re: [PATCH] irqchip/apple-aic: Only handle PMC interrupt as FIQ when
 configured to fire FIQ

Hi,


On Fri, Jan 17, 2025, at 18:02, Nick Chan wrote:
> The CPU PMU in Apple SoCs can be configured to fire its interrupt in one
> of several ways, and since Apple A11 one of the method is FIQ. Only handle
> the PMC interrupt as a FIQ when the CPU PMU has been configured to fire
> FIQs.
>
> Cc: stable@...r.kernel.org
> Fixes: c7708816c944 ("irqchip/apple-aic: Wire PMU interrupts")
> Signed-off-by: Nick Chan <towinchenmi@...il.com>
> ---
>  drivers/irqchip/irq-apple-aic.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/irqchip/irq-apple-aic.c 
> b/drivers/irqchip/irq-apple-aic.c
> index da5250f0155c..c3d435103d6d 100644
> --- a/drivers/irqchip/irq-apple-aic.c
> +++ b/drivers/irqchip/irq-apple-aic.c
> @@ -577,7 +577,8 @@ static void __exception_irq_entry 
> aic_handle_fiq(struct pt_regs *regs)
>  						  AIC_FIQ_HWIRQ(AIC_TMR_EL02_VIRT));
>  	}
> 
> -	if (read_sysreg_s(SYS_IMP_APL_PMCR0_EL1) & PMCR0_IACT) {
> +	if (read_sysreg_s(SYS_IMP_APL_PMCR0_EL1) &
> +	    (FIELD_PREP(PMCR0_IMODE, PMCR0_IMODE_FIQ) | PMCR0_IACT)) {

That's a somewhat unusual way to use FIELD_PREP and I'm not sure the
expression even does what you want. It's true when only PMCR0_IACT is set and
your commit description mentions that you only when to handle these when
FIQ have been configured. Am I missing something here?


Best,


Sven