[PATCH 1/1] powerpc/64: Adjust order in pcibios_init()

[Sam Bobroff]

Hey all,

After some consideration, I've decided to post a v2 of this patch that
will make it a bit safer (although I haven't seen any problems with it)
and make it a little easier to refactor some of the EEH code that
interacts with the hooks.

Cheers,
Sam.

On Thu, Feb 14, 2019 at 04:14:42PM +1100, Sam Bobroff wrote:
> The pcibios_init() function for 64 bit PowerPC currently calls
> pci_bus_add_devices() before pcibios_resource_survey(), which seems
> incorrect because it adds devices and attempts to bind their drivers
> before allocating their resources (although no problems seem to be
> apparent).
> 
> So move the call to pci_bus_add_devices() to after
> pcibios_resource_survey().
> 
> This will also allow the ppc_md.pcibios_bus_add_device() hooks to
> perform actions that depend on PCI resources, both during rescanning
> (where this is already the case) and at boot time, which should
> support improvements and refactoring.
> 
> Signed-off-by: Sam Bobroff <sbobroff at linux.ibm.com>
> ---
> Hi everyone,
> 
> I've tested this on a P9 for both the host and a KVM guest, and the change
> hasn't caused any differences in PCI resource assignments or the general boot
> messages.
> 
> I've also had a go at inspecting most of the code used by pci_bus_add_devices()
> and pcibios_resource_survey() and it doesn't look like there are going to be
> any changes in behaviour caused by reordering.  It might be worth mentioning
> that the hotplug path (see pcibios_finish_adding_to_bus()) already does
> resource allocation before calling pci_bus_add_devices().
> 
> However, it would be great if someone could test this change on some older
> hardware or comment on wether we should make the same change on 32 bit machines.
> 
> Cheers,
> Sam.
> 
>  arch/powerpc/kernel/pci_64.c | 8 +++++---
>  1 file changed, 5 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/powerpc/kernel/pci_64.c b/arch/powerpc/kernel/pci_64.c
> index 9d8c10d55407..1ce28888dbdb 100644
> --- a/arch/powerpc/kernel/pci_64.c
> +++ b/arch/powerpc/kernel/pci_64.c
> @@ -58,14 +58,16 @@ static int __init pcibios_init(void)
>  	pci_add_flags(PCI_ENABLE_PROC_DOMAINS | PCI_COMPAT_DOMAIN_0);
>  
>  	/* Scan all of the recorded PCI controllers.  */
> -	list_for_each_entry_safe(hose, tmp, &hose_list, list_node) {
> +	list_for_each_entry_safe(hose, tmp, &hose_list, list_node)
>  		pcibios_scan_phb(hose);
> -		pci_bus_add_devices(hose->bus);
> -	}
>  
>  	/* Call common code to handle resource allocation */
>  	pcibios_resource_survey();
>  
> +	/* Add devices. */
> +	list_for_each_entry_safe(hose, tmp, &hose_list, list_node)
> +		pci_bus_add_devices(hose->bus);
> +
>  	printk(KERN_DEBUG "PCI: Probing PCI hardware done\n");
>  
>  	return 0;
> -- 
> 2.19.0.2.gcad72f5712
> 
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