Re: [PATCH v1 05/14] xen/arm: PCI host bridge discovery within XEN on ARM

[Oleksandr Andrushchenko <Oleksandr_Andrushchenko@xxxxxxxx>]

Hi, Rahul!

On 19.08.21 15:02, Rahul Singh wrote:
> XEN during boot will read the PCI device tree node “reg” property
> and will map the PCI config space to the XEN memory.
[snip]
> +static struct pci_config_window *gen_pci_init(struct dt_device_node *dev,
> +                                              int ecam_reg_idx)
> +{
> +    int err;
> +    struct pci_config_window *cfg;
> +    paddr_t addr, size;
> +
> +    cfg = xzalloc(struct pci_config_window);
> +    if ( !cfg )
> +        return NULL;
> +
> +    err = dt_pci_parse_bus_range(dev, cfg);
> +    if ( !err ) {
> +        cfg->busn_start = 0;
> +        cfg->busn_end = 0xff;
> +        printk(XENLOG_ERR "%s:No bus range found for pci controller\n",
> +               dt_node_full_name(dev));
> +    } else {
> +        if ( cfg->busn_end > cfg->busn_start + 0xff )
> +            cfg->busn_end = cfg->busn_start + 0xff;
> +    }
> +
> +    /* Parse our PCI ecam register address*/
> +    err = dt_device_get_address(dev, ecam_reg_idx, &addr, &size);

I am a bit worried here that we don't get the reg index from the device tree,

but for generic ECAM we use reg[0] and for Xilinx we use reg[2].

For example, for Xilinx we have

reg = <0x00 0xfd0e0000 0x00 0x1000 0x00 0xfd480000 0x00 0x1000 0x80 0x00 0x00 
0x1000000>;
reg-names = "breg\0pcireg\0cfg";

so, we can parse the reg-names and understand that the configuration space is 
the last in the reg property.

The same I think can be done for other device trees probably.

Rahul, do you know if reg-names "cfg" is vendor specific of used widely?

Thank you,

Oleksandr