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    SubjectRe: [PATCH 3/3] ARM: gic: add OF based initialization
    On Mon, Sep 26, 2011 at 03:49:11PM -0500, Rob Herring wrote:
    > On 09/26/2011 02:57 PM, Jamie Iles wrote:
    > > Hi Rob,
    > >
    > > On Tue, Sep 20, 2011 at 03:24:04PM -0500, Rob Herring wrote:
    > > [...]
    > >> +int __init gic_of_init(struct device_node *node, struct device_node *parent)
    > >> +{
    > >> + void __iomem *cpu_base;
    > >> + void __iomem *dist_base;
    > >> + int irq;
    > >> + struct irq_domain *domain = &gic_data[gic_cnt].domain;
    > >> +
    > >> + if (WARN_ON(!node))
    > >> + return -ENODEV;
    > >> +
    > >> + dist_base = of_iomap(node, 0);
    > >> + WARN(!dist_base, "unable to map gic dist registers\n");
    > >> +
    > >> + cpu_base = of_iomap(node, 1);
    > >> + WARN(!cpu_base, "unable to map gic cpu registers\n");
    > >> +
    > >> + domain->nr_irq = gic_irq_count(dist_base);
    > >> + /* subtract off SGIs. Also subtract off PPIs for secondary GICs */
    > >> + if (parent)
    > >> + domain->nr_irq -= 32;
    > >> + else
    > >> + domain->nr_irq -= 16;
    > >> +
    > >> + domain->irq_base = irq_alloc_descs(-1, 16, domain->nr_irq, numa_node_id());
    > >
    > > The way I understand irq_alloc_descs() (probably not very well) is that
    > > having the irq parameter < 0 and the from parameter 16 means that it
    > > needs to find domain->nr_irq descs starting from at least 16. But if
    > > the base is greater than 16, does this still work with the gic entry
    > > macros as they are?
    >
    > No, but that would only happen if a platform calls irq_alloc_descs prior
    > to this code. The root controller must be initialized first (for other
    > reasons as well). There are no calls to irq_alloc_descs in arch/arm.
    >
    > With the MULTI_IRQ GIC support Marc Z is working on, we could make the
    > GIC irq mapping be completely dynamic. Although, there's probably not
    > much reason to do so for the root controller.

    OK, that makes sense. I think that if you were to do
    irq_alloc_descs(16, 16, domain->nr_irqs, num_node_id()) then that will
    guarantee the descriptors start from 16 (if they are available) which is
    probably nicer.

    Jamie


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