linux-kernel - Re: [PATCH V7] gic: preserve gic V2 bypass bits in cpu ctrl register

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Message-ID: <alpine.DEB.2.02.1405090042321.6261@ionos.tec.linutronix.de>
Date:	Fri, 9 May 2014 00:50:45 +0200 (CEST)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Feng Kan <fkan@....com>
cc:	catalin.marinas@....com, marc.zyngier@....com, will.deacon@....com,
	linux-kernel@...r.kernel.org, patches@....com,
	Vinayak Kale <vkale@....com>
Subject: Re: [PATCH V7] gic: preserve gic V2 bypass bits in cpu ctrl
 register

On Thu, 8 May 2014, Feng Kan 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>
> ---
> V7: cleanup white spaces, remove export in gic.h, change if_up to static.
> V6: add gic_cpu_if_up function to replace macro used in v5
> 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 |   30 +++++++++++++++++++++++++++---
>  1 files changed, 27 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/irqchip/irq-gic.c b/drivers/irqchip/irq-gic.c
> index 4300b66..7e952c3 100644
> --- a/drivers/irqchip/irq-gic.c
> +++ b/drivers/irqchip/irq-gic.c
> @@ -373,6 +373,20 @@ static u8 gic_get_cpumask(struct gic_chip_data *gic)
>  	return mask;
>  }
>  
> +static void gic_cpu_if_up(void)
> +{
> +	void __iomem *cpu_base = gic_data_cpu_base(&gic_data[0]);
> +	u32 bypass;
> +
> +	/*
> +	 * Preserve bypass disable bits to be written back later
> +	 */
> +	bypass = readl(cpu_base + GIC_CPU_CTRL);
> +	bypass &= 0x1e0;

Can we please use some reasonable defines instead of magic hex
constants?

It's not a new problem as the existing code is full of magic
numbers. But as a compensation for stealing so much of Marcs time for
this rather trivial endeavour, please create a patch series with two
patches:

1/2: Replace the existing magic constants in that code with reasonable
     self explaining defines

2/2: Add your new stuff on top of it.

Thanks,

	tglx
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