[PATCH kernel] powerpc/pci/of: Parse unassigned resources

[Alexey Kardashevskiy]

On 14/06/2019 12:59, Alexey Kardashevskiy wrote:
> The pseries platform uses the PCI_PROBE_DEVTREE method of PCI probing
> which is basically reading "assigned-addresses" of every PCI device.
> However if the property is missing or zero sized, then there is
> no fallback of any kind and the PCI resources remain undiscovered, i.e.
> pdev->resource[] array is empty.
> 
> This adds a fallback which parses the "reg" property in pretty much same
> way except it marks resources as "unset" which later makes Linux assign
> those resources with proper addresses.
> 
> Signed-off-by: Alexey Kardashevskiy <aik at ozlabs.ru>
> ---
> 
> This is an attempts to boot linux directly under QEMU without slof/rtas;
> the aim is to use petitboot instead and let the guest kernel configure
> devices.
> 
> QEMU does not allocate resources, it creates correct "reg" and zero length
> "assigned-addresses" (which is probably a bug on its own) which is
> normally populated by SLOF later but not during this exercise.
> 
> ---
>  arch/powerpc/kernel/pci_of_scan.c | 10 ++++++++++
>  1 file changed, 10 insertions(+)
> 
> diff --git a/arch/powerpc/kernel/pci_of_scan.c b/arch/powerpc/kernel/pci_of_scan.c
> index 64ad92016b63..cfe6ec3c6aaf 100644
> --- a/arch/powerpc/kernel/pci_of_scan.c
> +++ b/arch/powerpc/kernel/pci_of_scan.c
> @@ -82,10 +82,18 @@ static void of_pci_parse_addrs(struct device_node *node, struct pci_dev *dev)
>  	const __be32 *addrs;
>  	u32 i;
>  	int proplen;
> +	bool unset = false;
>  
>  	addrs = of_get_property(node, "assigned-addresses", &proplen);
>  	if (!addrs)
>  		return;


Ah. Of course, these 2 lines above should go, my bad. I'll repost if
there are no other (and bigger) problems with this.



> +	if (!addrs || !proplen) {
> +		addrs = of_get_property(node, "reg", &proplen);
> +		if (!addrs || !proplen)
> +			return;
> +		unset = true;
> +	}
> +
>  	pr_debug("    parse addresses (%d bytes) @ %p\n", proplen, addrs);
>  	for (; proplen >= 20; proplen -= 20, addrs += 5) {
>  		flags = pci_parse_of_flags(of_read_number(addrs, 1), 0);
> @@ -110,6 +118,8 @@ static void of_pci_parse_addrs(struct device_node *node, struct pci_dev *dev)
>  			continue;
>  		}
>  		res->flags = flags;
> +		if (unset)
> +			res->flags |= IORESOURCE_UNSET;
>  		res->name = pci_name(dev);
>  		region.start = base;
>  		region.end = base + size - 1;
> 

-- 
Alexey