Re: [Xen-devel] [PATCH v5 17/22] xen/arm: ITS: Initialize physical ITS

[Julien Grall <julien.grall@xxxxxxxxxx>]

Hi Vijay,

On 27/07/2015 04:11, vijay.kilari@xxxxxxxxx wrote:
> From: Vijaya Kumar K <Vijaya.Kumar@xxxxxxxxxxxxxxxxxx>
>
> Initialize physical ITS driver from GIC v3 driver
> if LPIs are supported by hardware
>
> Signed-off-by: Vijaya Kumar K <Vijaya.Kumar@xxxxxxxxxxxxxxxxxx>
> ---
> v5: Made check of its dt node availability before
>      setting lpi_supported flag
> ---
>   xen/arch/arm/gic-v3.c |   19 +++++++++++++++----
>   1 file changed, 15 insertions(+), 4 deletions(-)
>
> diff --git a/xen/arch/arm/gic-v3.c b/xen/arch/arm/gic-v3.c
> index 8c7c5cf..23eb47c 100644
> --- a/xen/arch/arm/gic-v3.c
> +++ b/xen/arch/arm/gic-v3.c
> @@ -714,6 +714,10 @@ static int __cpuinit gicv3_cpu_init(void)
>       if ( gicv3_enable_redist() )
>           return -ENODEV;
>
> +        /* Give LPIs a spin */
> +    if ( gicv3_info.lpi_supported )
> +        its_cpu_init();
> +
>       /* Set priority on PPI and SGI interrupts */
>       priority = (GIC_PRI_IPI << 24 | GIC_PRI_IPI << 16 | GIC_PRI_IPI << 8 |
>                   GIC_PRI_IPI);
> @@ -1323,11 +1327,18 @@ static int __init gicv3_init(void)
>
>       if ( gicv3_dist_supports_lpis() )
>       {
> -        gicv3_info.lpi_supported = 1;
> -        gicv3_info.nr_event_ids = its_get_nr_event_ids();
> +        /*
> +         * LPI support is enabled only if HW supports it and
> +         * ITS dt node is available
> +         */
> +        if ( !its_init(&gicv3.rdist_data) )
> +        {
> +            gicv3_info.lpi_supported = 1;
> +            gicv3_info.nr_event_ids = its_get_nr_event_ids();
> +        }
> +        else
> +            gicv3_info.lpi_supported = 0;
I think this is wrong to use LPI supported to know whether ITS is 
present or not.
AFAICT, most the usage of lpi_supported is only for vgic where you 
should have a proper field in the vgic structure rather than using this 
field.
For the rest, we may want to support LPIs without ITS at some point. So 
we should keep 2 distincts field for this purpose. Although, I believe 
that we can drop most of them.
>       }
> -    else
> -        gicv3_info.lpi_supported = 0;
Why did you drop the else? It was valid...

>       gicv3_dist_init();
>       res = gicv3_cpu_init();
Regards,


--
Julien Grall

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