[PATCH 1/6] irqchip: add the Alpine MSIX interrupt controller

Antoine Tenart
2016-02-08T10:44:07Z

On Mon, Feb 08, 2016 at 10:32:08AM +0000, Marc Zyngier wrote:
> On 08/02/16 10:26, Antoine Tenart wrote:
> >>> +static int alpine_msix_init(struct device_node *node,
> >>> + struct device_node *parent)
> >>> +{
> >>> + struct alpine_msix_data *priv;
> >>> + struct resource res;
> >>> + int ret;
> >>> +
> >>> + priv = kzalloc(sizeof(*priv), GFP_KERNEL);
> >>> + if (!priv)
> >>> + return -ENOMEM;
> >>> +
> >>> + spin_lock_init(&priv->msi_map_lock);
> >>> +
> >>> + ret = of_address_to_resource(node, 0, &res);
> >>> + if (ret) {
> >>> + pr_err("Failed to allocate resource\n");
> >>> + goto err_priv;
> >>> + }
> >>> +
> >>> + priv->addr_high = upper_32_bits((u64)res.start);
> >>> + priv->addr_low = lower_32_bits(res.start) + ALPINE_MSIX_SPI_TARGET_CLUSTER0;
> >>
> >> This is a bit odd. If you always set bit 16, why isn't that reflected in
> >> the base address coming from the DT?
> >
> > The 20 least significant bits of addr_low provide direct information
> > regarding the interrupt destination, so I thought it would be clearer
> > to have this explicitly in the driver so that we know what those bits
> > mean.
>
> So what is this information? TARGET_CLUSTER0 is not very expressive, and
> doesn't show what the alternatives are. Could you please elaborate a bit
> on that front?

For now lots of bits are reserved, so there aren't many alternatives.
Bits [18:17] are used to set the GIC to which to route the MSI and bit
16 must be set when this target GIC is the primary GIC (bits [18:17] set
to 0x0). There aren't other options available for now (that I'm aware
of) for the target GIC configuration.

Antoine

--
Antoine T?nart, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com
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