Re: [PATCH v4 1/2] bcma: register bcma as device tree driver

Arnd Bergmann
2014-09-24T09:48:18Z

On Wednesday 24 September 2014 00:04:18 Hauke Mehrtens wrote:
> I assume this should then look somehow like this:
>
> axi@18000000 {
> compatible = "brcm,bus-axi";
> reg = <0x18000000 0x1000>;
> ranges = <0x00000000 0x18000000 0x00100000>;
> #address-cells = <1>;
> #size-cells = <1>;
>
> #interrupt-cells = <1>;
> interrupt-map = <
> /* ChipCommon */
> 0x00000000 0 &gic GIC_SPI 85 IRQ_TYPE_LEVEL_HIGH
>
> /* PCIe Controller 0 */
> 0x00012000 0 &gic GIC_SPI 126 IRQ_TYPE_LEVEL_HIGH
> 0x00012000 1 &gic GIC_SPI 127 IRQ_TYPE_LEVEL_HIGH
> 0x00012000 2 &gic GIC_SPI 128 IRQ_TYPE_LEVEL_HIGH
> 0x00012000 3 &gic GIC_SPI 129 IRQ_TYPE_LEVEL_HIGH
> 0x00012000 4 &gic GIC_SPI 130 IRQ_TYPE_LEVEL_HIGH
> 0x00012000 5 &gic GIC_SPI 131 IRQ_TYPE_LEVEL_HIGH
>
> /* USB 2.0 Controller */
> 0x00021000 0 &gic GIC_SPI 79 IRQ_TYPE_LEVEL_HIGH
> >;
> };

Right, although I would add a few more '<', '>' and ',' for readability,
separating each line with a comma.

You are also missing an 'interrupt-map-mask' property that lists which
bits of the address are significant.

Are the interrupt numbers you have in the example (0, 0, 1, 2, ... 5, 0)
the actual numbers that are present in the hw registers?

> How does the mapping of these interrupts to the devices work?

The same way that of_irq_parse_and_map_pci() works (the second half of it).
It's a very similar situation: you have a discoverable bus on which the
interrupts are listed in a different domain from which they are supposed to
be on the parent. The trick is to make up your own address property
and of_phandle_args on the stack and fill that with the data from
the hw bus scan, so you can get into the middle of the normal DT
irq code that gets them from device nodes.

> Do I have to add a device tree entry for every device after all?

No, unless you want to add other properties in the node, such as
a MAC address, but then you still only need some of the devices.

> Do you have some example code where this is handled in code, I could not
> find the code doing this for PCI.

drivers/of/of_pci_irq.c, though the hard part is done in drivers/of/irq.c,
which parses the interrupt-map and interrupt-map-mask properties.

Arnd