linux-kernel - Re: [PATCH V5] gic: preserve gic V2 bypass bits in cpu ctrl register

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Date:	Thu, 08 May 2014 13:54:27 +0100
From:	Marc Zyngier <marc.zyngier@....com>
To:	Feng Kan <fkan@....com>
Cc:	"tglx\@linutronix.de" <tglx@...utronix.de>,
	Catalin Marinas <Catalin.Marinas@....com>,
	Will Deacon <Will.Deacon@....com>,
	"linux-kernel\@vger.kernel.org" <linux-kernel@...r.kernel.org>,
	Vinayak Kale <vkale@....com>
Subject: Re: [PATCH V5] gic: preserve gic V2 bypass bits in cpu ctrl register

On Thu, May 08 2014 at  1:01:50 am BST, Feng Kan <fkan@....com> wrote:
> This change is made to preserve the GIC v2 bypass bits in the
> GIC_CPU_CTRL register (also known as the GICC_CTLR register in spec).
> This code will preserve all bits configured by the bootload regarding
> v2 bypass group bits. In the X-Gene platform, the bypass functionality
> is not used and bypass bits should not be changed by the kernel gic
> code as it could lead to incorrect behavior.
>
> Signed-off-by: Vinayak Kale <vkale@....com>
> Acked-by: Anup Patel <apatel@....com>
> Signed-off-by: Feng Kan <fkan@....com>
> ---
> V5: Use macro to replace read modify write of cpu_ctrl register.
> V4: Change to use bypass mask, change ot user more suitable variable name.
>  drivers/irqchip/irq-gic.c |   16 +++++++++++++---
>  1 files changed, 13 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/irqchip/irq-gic.c b/drivers/irqchip/irq-gic.c
> index 4300b66..42e9bf4 100644
> --- a/drivers/irqchip/irq-gic.c
> +++ b/drivers/irqchip/irq-gic.c
> @@ -97,6 +97,13 @@ struct irq_chip gic_arch_extn = {
>  #define MAX_GIC_NR	1
>  #endif
>  
> +#define set_cpuctrl(base, val)					\
> +	do {							\
> +		u32 bypass;					\
> +		bypass = readl(base + GIC_CPU_CTRL) & 0x1e0;	\
> +		writel_relaxed(bypass | val, base + GIC_CPU_CTRL);\
> +	} while (0)
> +

Please use a function. A macro doesn't buy us anything here, and lacks
type safety.

Your previous patch was nicer in that respect. You just had to move the
enable code to a gic_cpu_if_up() function, and you were done...

>  static struct gic_chip_data gic_data[MAX_GIC_NR] __read_mostly;
>  
>  #ifdef CONFIG_GIC_NON_BANKED
> @@ -449,13 +456,15 @@ static void gic_cpu_init(struct gic_chip_data *gic)
>  		writel_relaxed(0xa0a0a0a0, dist_base + GIC_DIST_PRI + i * 4 / 4);
>  
>  	writel_relaxed(0xf0, base + GIC_CPU_PRIMASK);
> -	writel_relaxed(1, base + GIC_CPU_CTRL);
> +
> +	set_cpuctrl(base, 1);
>  }
>  
>  void gic_cpu_if_down(void)
>  {
>  	void __iomem *cpu_base = gic_data_cpu_base(&gic_data[0]);
> -	writel_relaxed(0, cpu_base + GIC_CPU_CTRL);
> +
> +	set_cpuctrl(cpu_base, 0);
>  }
>  
>  #ifdef CONFIG_CPU_PM
> @@ -590,7 +599,8 @@ static void gic_cpu_restore(unsigned int gic_nr)
>  		writel_relaxed(0xa0a0a0a0, dist_base + GIC_DIST_PRI + i * 4);
>  
>  	writel_relaxed(0xf0, cpu_base + GIC_CPU_PRIMASK);
> -	writel_relaxed(1, cpu_base + GIC_CPU_CTRL);
> +	
> +	set_cpuctrl(cpu_base, 1);
>  }
>  
>  static int gic_notifier(struct notifier_block *self, unsigned long cmd,	void *v)


	M.
-- 
Jazz is not dead. It just smells funny.
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