linux-kernel - Re: [PATCH 2/3] ARM: gic: Use cpu pm notifiers to save gic state

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Date:	Mon, 13 Jun 2011 11:41:45 +0100
From:	Lorenzo Pieralisi <lorenzo.pieralisi@....com>
To:	Colin Cross <ccross@...roid.com>
Cc:	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Russell King <linux@....linux.org.uk>,
	Catalin Marinas <Catalin.Marinas@....com>,
	Abhijeet Dharmapurikar <adharmap@...eaurora.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Santosh Shilimkar <santosh.shilimkar@...com>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH 2/3] ARM: gic: Use cpu pm notifiers to save gic state

Hi Colin,

On Mon, Jun 13, 2011 at 01:43:44AM +0100, Colin Cross wrote:
> When the cpu is powered down in a low power mode, the gic cpu
> interface may be reset, and when the cpu complex is powered
> down, the gic distributor may also be reset.
> 
> This patch uses CPU_PM_ENTER and CPU_PM_EXIT notifiers to save
> and restore the gic cpu interface registers, and the
> CPU_COMPLEX_PM_ENTER and CPU_COMPLEX_PM_EXIT notifiers to save
> and restore the gic distributor registers.
> 
> Signed-off-by: Colin Cross <ccross@...roid.com>
> ---
>  arch/arm/common/gic.c |  212 +++++++++++++++++++++++++++++++++++++++++++++++++
>  1 files changed, 212 insertions(+), 0 deletions(-)
> 

[...]

> +
> +static void __init gic_cpu_pm_init(struct gic_chip_data *gic)
> +{
> +	gic->saved_ppi_enable = __alloc_percpu(DIV_ROUND_UP(32, 32) * 4,
> +		sizeof(u32));
> +	BUG_ON(!gic->saved_ppi_enable);
> +
> +	gic->saved_ppi_conf = __alloc_percpu(DIV_ROUND_UP(32, 16) * 4,
> +		sizeof(u32));
> +	BUG_ON(!gic->saved_ppi_conf);
> +
> +	gic->saved_ppi_pri = __alloc_percpu(DIV_ROUND_UP(32, 4) * 4,
> +		sizeof(u32));
> +	BUG_ON(!gic->saved_ppi_pri);
> +
> +	cpu_pm_register_notifier(&gic_notifier_block);
> +}
> +#else
> +static void __init gic_cpu_pm_init(struct gic_chip_data *gic)
> +{
> +}
> +#endif
> +
>  void __init gic_init(unsigned int gic_nr, unsigned int irq_start,
>  	void __iomem *dist_base, void __iomem *cpu_base)
>  {
> @@ -367,6 +578,7 @@ void __init gic_init(unsigned int gic_nr, unsigned int irq_start,
>  
>  	gic_dist_init(gic, irq_start);
>  	gic_cpu_init(gic);
> +	gic_cpu_pm_init(gic);
>  }
>  
> 

I have been using this patchset for a while and it works perfectly fine.
I reckon one bit we could improve is allowing to register a subsystem depending
on a flag set @init, for now it is a save "all default registered subsystems or nothing" solution on cpu_pm_enter(), maybe we could add this level of
configurability as an improvement (GIC being a good example, see OMAP).

Lorenzo

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