Re: [PATCH V2 03/10] irqchip,GICv3,ACPI: Add redistributor support via GICC structures.

[Tomasz Nowicki]

On 12.01.2016 17:16, Marc Zyngier wrote:
> > > >>Also, the spec says:
> > > >>
> > > >>"On systems supporting GICv3 and above, this field holds the 64-bit
> > > >>physical address of the associated Redistributor. If all of the GIC
> > > >>Redistributors are in the always-on power domain, GICR structures should
> > > >>be used to describe the Redistributors instead, and this field must be
> > > >>set to 0."
> > > >>
> > > >>which triggers two questions:
> > > >>- Can you access always the GICR_TYPER register without waking the
> > > >>redistributor up?
> > >
> > >I missed this part, can you suggest how can we do that? accessing some
> > >register before access to redistributor?
> This redistributor may be in a power-domain that is off. Are you
> guaranteed that you can access GICR_TYPER even when it is off?
>
> > >
> > > >>- How do you cope with situations where some redistributors are in the
> > > >>always-on domain, and some are not?
> > >
> > >I'm not sure if there is such hardware, if yes, do we need to fix
> > >the spec first?
> It is something that should definitely be clarified. Can we end-up in a
> situation where some redistributors are described via the GICR
> structure, and some via the GICC structure? The spec is a bit ambiguous.

To recap:
1. GICR and GICC subtables should be mutually exclusive, but ACPI spec 
should be clear about this.
2. We need to know if we can access GICR_TYPER without waking the 
redistributor up.

Tirumalesh, can you please advice?

Tomasz