linux-kernel - Re: [PATCH v2 2/4] PCI: pci-host-generic: Fix lookup of linux,pci-probe-only property

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Date:	Fri, 14 Aug 2015 11:40:51 -0500
From:	Bjorn Helgaas <bhelgaas@...gle.com>
To:	Marc Zyngier <marc.zyngier@....com>
Cc:	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Paul Mackerras <paulus@...ba.org>,
	Michael Ellerman <mpe@...erman.id.au>,
	Will Deacon <will.deacon@....com>,
	Suravee Suthikulpanit <Suravee.Suthikulpanit@....com>,
	Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
	Grant Likely <grant.likely@...aro.org>,
	Rob Herring <robh+dt@...nel.org>,
	Alexander Graf <agraf@...e.de>, linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	linuxppc-dev@...ts.ozlabs.org, linux-pci@...r.kernel.org,
	devicetree@...r.kernel.org
Subject: Re: [PATCH v2 2/4] PCI: pci-host-generic: Fix lookup of
 linux,pci-probe-only property

On Fri, Aug 14, 2015 at 05:19:17PM +0100, Marc Zyngier wrote:
> When pci-host-generic looks for the probe-only property, it seems
> to trust the DT to be correctly written, and assumes that there
> is a parameter to the property.
> 
> Unfortunately, this is not always the case, and some firmware expose
> this property naked. The driver ends up making a decision based on
> whatever the property pointer points to, which is likely to be junk.
> 
> Switch to the common of_pci.c implementation that doesn't suffer
> from this problem.
> 
> Signed-off-by: Marc Zyngier <marc.zyngier@....com>
> ---
>  drivers/pci/host/pci-host-generic.c | 9 +--------
>  1 file changed, 1 insertion(+), 8 deletions(-)
> 
> diff --git a/drivers/pci/host/pci-host-generic.c b/drivers/pci/host/pci-host-generic.c
> index 265dd25..545ff4e 100644
> --- a/drivers/pci/host/pci-host-generic.c
> +++ b/drivers/pci/host/pci-host-generic.c
> @@ -210,7 +210,6 @@ static int gen_pci_probe(struct platform_device *pdev)
>  	int err;
>  	const char *type;
>  	const struct of_device_id *of_id;
> -	const int *prop;
>  	struct device *dev = &pdev->dev;
>  	struct device_node *np = dev->of_node;
>  	struct gen_pci *pci = devm_kzalloc(dev, sizeof(*pci), GFP_KERNEL);
> @@ -225,13 +224,7 @@ static int gen_pci_probe(struct platform_device *pdev)
>  		return -EINVAL;
>  	}
>  
> -	prop = of_get_property(of_chosen, "linux,pci-probe-only", NULL);
> -	if (prop) {
> -		if (*prop)
> -			pci_add_flags(PCI_PROBE_ONLY);
> -		else
> -			pci_clear_flags(PCI_PROBE_ONLY);
> -	}
> +	of_pci_check_probe_only(of_chosen);

Do we need support for pci-probe-only in pci-host-generic at all?
You're removing the use in amd-overdrive.dts, and there are no other
DTs in the kernel tree that mention it.

If we can live without it, that would be nice.  It seems like a relic from
days when we couldn't reliably assign resources.  (I'm not saying we can do
that reliably even today, but I'd rather make it reliable than turn it
off.)

>  	of_id = of_match_node(gen_pci_of_match, np);
>  	pci->cfg.ops = of_id->data;
> -- 
> 2.1.4
> 
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