linux-kernel - Re: [PATCH 2/3] irqchip/mips-gic: Get rid of the reliance on irq_cpu

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Date:   Fri, 22 Oct 2021 16:57:35 +0300
From:   Serge Semin <fancer.lancer@...il.com>
To:     Marc Zyngier <maz@...nel.org>
Cc:     Serge Semin <Sergey.Semin@...kalelectronics.ru>,
        linux-mips@...r.kernel.org, linux-kernel@...r.kernel.org,
        Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        Huacai Chen <chenhuacai@...nel.org>,
        Jiaxun Yang <jiaxun.yang@...goat.com>, f.fainelli@...il.com,
        Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH 2/3] irqchip/mips-gic: Get rid of the reliance on
 irq_cpu_online()

On Thu, Oct 21, 2021 at 06:04:13PM +0100, Marc Zyngier wrote:
> The MIPS GIC driver uses irq_cpu_online() to go and program the
> per-CPU interrupts. However, this method iterates over all IRQs
> in the system, despite only 3 per-CPU interrupts being of interest.
> 
> Let's be terribly bold and do the iteration ourselves. To ensure
> mutual exclusion, hold the gic_lock spinlock that is otherwise
> taken while dealing with these interrupts.

Please consider a nitpick below. Other than that looks good:
Reviewed-by: Serge Semin <fancer.lancer@...il.com>

> 
> Signed-off-by: Marc Zyngier <maz@...nel.org>
> ---
>  drivers/irqchip/irq-mips-gic.c | 37 ++++++++++++++++++++++++----------
>  1 file changed, 26 insertions(+), 11 deletions(-)
> 
> diff --git a/drivers/irqchip/irq-mips-gic.c b/drivers/irqchip/irq-mips-gic.c
> index 54c7092cc61d..45c83dd804a0 100644
> --- a/drivers/irqchip/irq-mips-gic.c
> +++ b/drivers/irqchip/irq-mips-gic.c
> @@ -381,24 +381,35 @@ static void gic_unmask_local_irq_all_vpes(struct irq_data *d)
>  	spin_unlock_irqrestore(&gic_lock, flags);
>  }
>  
> -static void gic_all_vpes_irq_cpu_online(struct irq_data *d)
> +static void gic_all_vpes_irq_cpu_online(void)
>  {
> -	struct gic_all_vpes_chip_data *cd;
> -	unsigned int intr;

> +	static unsigned int local_intrs[] = {

What about adding 'const' here?

-Sergey

> +		GIC_LOCAL_INT_TIMER,
> +		GIC_LOCAL_INT_PERFCTR,
> +		GIC_LOCAL_INT_FDC,
> +	};
> +	unsigned long flags;
> +	int i;
>  
> -	intr = GIC_HWIRQ_TO_LOCAL(d->hwirq);
> -	cd = irq_data_get_irq_chip_data(d);
> +	spin_lock_irqsave(&gic_lock, flags);
>  
> -	write_gic_vl_map(mips_gic_vx_map_reg(intr), cd->map);
> -	if (cd->mask)
> -		write_gic_vl_smask(BIT(intr));
> +	for (i = 0; i < ARRAY_SIZE(local_intrs); i++) {
> +		unsigned int intr = local_intrs[i];
> +		struct gic_all_vpes_chip_data *cd;
> +
> +		cd = &gic_all_vpes_chip_data[intr];
> +		write_gic_vl_map(mips_gic_vx_map_reg(intr), cd->map);
> +		if (cd->mask)
> +			write_gic_vl_smask(BIT(intr));
> +	}
> +
> +	spin_unlock_irqrestore(&gic_lock, flags);
>  }
>  
>  static struct irq_chip gic_all_vpes_local_irq_controller = {
>  	.name			= "MIPS GIC Local",
>  	.irq_mask		= gic_mask_local_irq_all_vpes,
>  	.irq_unmask		= gic_unmask_local_irq_all_vpes,
> -	.irq_cpu_online		= gic_all_vpes_irq_cpu_online,
>  };
>  
>  static void __gic_irq_dispatch(void)
> @@ -477,6 +488,10 @@ static int gic_irq_domain_map(struct irq_domain *d, unsigned int virq,
>  	intr = GIC_HWIRQ_TO_LOCAL(hwirq);
>  	map = GIC_MAP_PIN_MAP_TO_PIN | gic_cpu_pin;
>  
> +	/*
> +	 * If adding support for more per-cpu interrupts, keep the the
> +	 * array in gic_all_vpes_irq_cpu_online() in sync.
> +	 */
>  	switch (intr) {
>  	case GIC_LOCAL_INT_TIMER:
>  		/* CONFIG_MIPS_CMP workaround (see __gic_init) */
> @@ -663,8 +678,8 @@ static int gic_cpu_startup(unsigned int cpu)
>  	/* Clear all local IRQ masks (ie. disable all local interrupts) */
>  	write_gic_vl_rmask(~0);
>  
> -	/* Invoke irq_cpu_online callbacks to enable desired interrupts */
> -	irq_cpu_online();
> +	/* Enable desired interrupts */
> +	gic_all_vpes_irq_cpu_online();
>  
>  	return 0;
>  }
> -- 
> 2.30.2
>