Re: [PATCH v3][UPDATE] ARM/PCI: claim bus resources on PCI_PROBE_ONLY set-ups

[Bjorn Helgaas <helgaas@kernel.org>]

On Thu, Jun 23, 2016 at 11:36:22AM +0100, Lorenzo Pieralisi wrote:
> The PCI bios API does not reassign bus resources on systems
> that require the BARs set-up to be immutable (ie PCI_PROBE_ONLY) since
> that would trigger system failures. Nonetheless, PCI bus resources
> allocated to PCI bridge and devices must be claimed in order to be
> validated and inserted in the kernel resource tree, but the current
> code omits the resources claiming and relies on arch specific kludges
> to prevent probing failure (ie preventing resources enablement on
> PCI_PROBE_ONLY systems).
> 
> Add code to the ARM PCI bios kernel layer that correctly claims bus
> resources upon probe on systems that are required to prevent
> reassignment after bus enumeration, so that the allocated resources
> can be enabled successfully upon PCI device drivers probing, without
> resorting to arch back-ends workarounds.
> 
> Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
> Cc: Bjorn Helgaas <bhelgaas@google.com>
> Cc: Russell King <linux@armlinux.org.uk>
> ---
> Hi Bjorn,
> 
> I put together this patch as requested, I could not test this
> specific path but I do not really see how this patch would
> affect any existing set-up.
> 
> It completes (and should be inserted as patch 2 or 3 for
> bisection reasons) this series:
> 
> https://patchwork.ozlabs.org/patch/632161/
> 
> Please let me know if that's ok.

Yes, this is exactly what I had in mind.  Then all the places that use
PCI_PROBE_ONLY will make sense when we look at them later.  I'll add
this to the series on pci/resource.

Thanks!

>  arch/arm/kernel/bios32.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/arm/kernel/bios32.c b/arch/arm/kernel/bios32.c
> index 488545f..1e05d04 100644
> --- a/arch/arm/kernel/bios32.c
> +++ b/arch/arm/kernel/bios32.c
> @@ -515,7 +515,9 @@ void pci_common_init_dev(struct device *parent, struct hw_pci *hw)
>  	list_for_each_entry(sys, &head, node) {
>  		struct pci_bus *bus = sys->bus;
>  
> -		if (!pci_has_flag(PCI_PROBE_ONLY)) {
> +		if (pci_has_flag(PCI_PROBE_ONLY)) {
> +			pci_bus_claim_resources(bus);
> +		} else {
>  			struct pci_bus *child;
>  
>  			/*
> -- 
> 2.6.4
> 
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