On 14.08.2015, at 09:43, Will Deacon [off-list ref] wrote:
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On Fri, Aug 14, 2015 at 05:40:51PM +0100, Bjorn Helgaas wrote:

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On Fri, Aug 14, 2015 at 05:19:17PM +0100, Marc Zyngier wrote:

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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.
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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.
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Switch to the common of_pci.c implementation that doesn't suffer
from this problem.
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Signed-off-by: Marc Zyngier <redacted>
---
drivers/pci/host/pci-host-generic.c | 9 +--------
1 file changed, 1 insertion(+), 8 deletions(-)
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diff --git a/drivers/pci/host/pci-host-generic.c =

b/drivers/pci/host/pci-host-generic.c

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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)

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	int err;
	const char *type;
	const struct of_device_id *of_id;
-	const int *prop;
	struct device *dev =3D &pdev->dev;
	struct device_node *np =3D dev->of_node;
	struct gen_pci *pci =3D devm_kzalloc(dev, sizeof(*pci), =

GFP_KERNEL);

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@@ -225,13 +224,7 @@ static int gen_pci_probe(struct platform_device =

*pdev)

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		return -EINVAL;
	}
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-	prop =3D of_get_property(of_chosen, "linux,pci-probe-only", =

NULL);

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-	if (prop) {
-		if (*prop)
-			pci_add_flags(PCI_PROBE_ONLY);
-		else
-			pci_clear_flags(PCI_PROBE_ONLY);
-	}
+	of_pci_check_probe_only(of_chosen);

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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.
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If we can live without it, that would be nice.  It seems like a relic =

from

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days when we couldn't reliably assign resources.  (I'm not saying we =

can do

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that reliably even today, but I'd rather make it reliable than turn =

it

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off.)

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Kvmtool certainly uses it (and generates its own DT, hence why you =

don't

see it in mainline). Not sure about qemu, though.

QEMU definitely doesn't do proble-only. Is this driver used on real PPC =
machines too? In that case you also won't see the dt, because it comes =
with the hardware ;).


Alex