Re: [PATCH v2 02/19] arm64: initial support for GICv3

[Z Lim <zlim.lnx@xxxxxxxxx>]

Hi Marc,

On Mon, Mar 24, 2014 at 4:10 AM, Marc Zyngier <marc.zyngier@xxxxxxx> wrote:
>
> Hi Zi,
>
> On 22/03/14 01:21, Zi Shen Lim wrote:
> > Hi Marc,
> >
> > On Thu, Mar 20, 2014 at 4:52 AM, Marc Zyngier <marc.zyngier@xxxxxxx
> > <mailto:marc.zyngier@xxxxxxx>> wrote:
> > <snip>
> >
> >
> >     +       /*
> >     +        * Find out how many interrupts are supported.
> >     +        * The GIC only supports up to 1020 interrupt sources
> >     (SGI+PPI+SPI)
> >     +        */
> >     +       gic_irqs = readl_relaxed(gic_data.dist_base + GICD_TYPER) &
> >     0x1f;
> >     +       gic_irqs = (gic_irqs + 1) * 32;
> >     +       if (gic_irqs > 1020)
> >     +               gic_irqs = 1020;
> >     +       gic_data.irq_nr = gic_irqs;
> >     +
> >     +       gic_data.domain = irq_domain_add_linear(node, gic_irqs - 16,
> >     +                                               &gic_irq_domain_ops,
> >     &gic_data);
> >
> >
> > Why gic_irqs - 16?
>
> Because we keep the SGIs (all 16 of them) for the core kernel (drivers
> are not allowed to request them).
>
> >
> >     __irq_domain_add(of_node, size, size, 0, ops, host_data);
> >
> >         domain->hwirq_max = hwirq_max;
> >
> >
> > So hwirq_max is effectively set to actual_hwirq_max-16.
> >
> > Later, the following warning can be triggered:
> >
> >     int irq_domain_associate(struct irq_domain *domain, unsigned int virq,
> >                              irq_hw_number_t hwirq)
> >     {
> >             struct irq_data *irq_data = irq_get_irq_data(virq);
> >             int ret;
> >
> >             if (WARN(hwirq >= domain->hwirq_max,
> >                      "error: hwirq 0x%x is too large for %s\n",
> >     (int)hwirq, domain->name))
> >                     return -EINVAL;
>
> Do you actually see this warning being triggered? I don't. We're using a
> linear domain that doesn't call into this function.

I see this warning :(
You can trigger it when a device's INT# falls within [gic_irqs-16, gic_irqs), which lines up with the -16 above.

irq_create_of_mapping  // SPI# from DT

domain->ops->xlate (gic_irq_domain_xlate)  // SPI# + 32 = INT# = hwirq

irq_create_mapping  // uses hwirq = INT#

irq_domain_associate  // uses hwirq = INT#

if (WARN(hwirq >= domain->hwirq_max, "error: hwirq 0x%x is too large for %s\n", (int)hwirq, domain->name))  // hwirq_max was set to (MAX_INT# - 16) above, uh oh...

>
> What am I missing?
>
> Cheers,
>
>         M.
> --
> Jazz is not dead. It just smells funny...

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