linux-kernel - Re: [RFC PATCH 23/33] irqchip/gic-v3-its: Add VPENDBASER/VPROPBASER accessors

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Date:   Mon, 13 Feb 2017 17:39:23 -0600
From:   Shanker Donthineni <shankerd@...eaurora.org>
To:     Marc Zyngier <marc.zyngier@....com>, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.cs.columbia.edu
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Jason Cooper <jason@...edaemon.net>
Subject: Re: [RFC PATCH 23/33] irqchip/gic-v3-its: Add VPENDBASER/VPROPBASER
 accessors

Hi Marc,


On 01/17/2017 04:20 AM, Marc Zyngier wrote:
> V{PEND,PROP}BASER being 64bit registers, they need some ad-hoc
> accessors on 32bit, specially given that VPENDBASER contains
> a Valid bit, making the access a bit convoluted.
>
> Signed-off-by: Marc Zyngier <marc.zyngier@....com>
> ---
>   arch/arm/include/asm/arch_gicv3.h   | 28 ++++++++++++++++++++++++++++
>   arch/arm64/include/asm/arch_gicv3.h |  5 +++++
>   2 files changed, 33 insertions(+)
>
> diff --git a/arch/arm/include/asm/arch_gicv3.h
> b/arch/arm/include/asm/arch_gicv3.h
> index 2747590..3f18832 100644
> --- a/arch/arm/include/asm/arch_gicv3.h
> +++ b/arch/arm/include/asm/arch_gicv3.h
> @@ -291,5 +291,33 @@ static inline u64 __gic_readq_nonatomic(const
> volatile void __iomem *addr)
>    */
>   #define gits_write_cwriter(v, c)	__gic_writeq_nonatomic(v, c)
>   
> +/*
> + * GITS_VPROPBASER - hi and lo bits may be accessed independently.
> + */
> +#define gits_write_vpropbaser(v, c)	__gic_writeq_nonatomic(v, c)
> +
> +/*
> + * GITS_VPENDBASER - the Valid bit must be cleared before changing
> + * anything else.
> + */
> +static inline void gits_write_vpendbaser(u64 val, void * __iomem addr)
> +{
> +	u32 tmp;
> +
> +	tmp = readl_relaxed(addr + 4);
> +	if (tmp & GICR_PENDBASER_Valid) {
> +		tmp &= ~GICR_PENDBASER_Valid;
> +		writel_relaxed(tmp, addr + 4);
> +	}
> +
> +	/*
> +	 * Use the fact that __gic_writeq_nonatomic writes the second
> +	 * half of the 64bit quantity after the first.
> +	 */
> +	__gic_writeq_nonatomic(val, addr);
I'm not sure whether software has to check a register write pending bit 
GICR_CTLR.RWP or not. GICv3 spec says, the effect of a write to 
GICR_VPENDBASER register is not guaranteed to be visible throughout the 
affinity hierarchy,as indicated by GICR_CTLR.RWP == 0.

-- 
Shanker Donthineni
Qualcomm Datacenter Technologies, Inc. as an affiliate of Qualcomm Technologies, Inc.
Qualcomm Technologies, Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project.