linux-kernel - Re: [PATCH v3 05/11] PCI: beef up pci_do_scan

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Date:	Thu, 12 Mar 2009 17:22:26 -0600
From:	Alex Chiang <achiang@...com>
To:	Kenji Kaneshige <kaneshige.kenji@...fujitsu.com>
Cc:	jbarnes@...tuousgeek.org, linux-pci@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 05/11] PCI: beef up pci_do_scan_bus()

Hello Kenji-san,

* Kenji Kaneshige <kaneshige.kenji@...fujitsu.com>:
> Alex Chiang wrote:
> > We have a nice interface for re-scanning a PCI bus which will
> > discover newly added devices, add them to the device tree, and
> > enable them properly.
> > 
> > Ensure that the bridge resources are properly sized and assigned
> > during the rescan.
> > 
> > Signed-off-by: Alex Chiang <achiang@...com>
> > ---
> > 
> >  drivers/pci/hotplug-pci.c |   16 ++++++++++++----
> >  1 files changed, 12 insertions(+), 4 deletions(-)
> > 
> > diff --git a/drivers/pci/hotplug-pci.c b/drivers/pci/hotplug-pci.c
> > index 4d4a644..33ab2d2 100644
> > --- a/drivers/pci/hotplug-pci.c
> > +++ b/drivers/pci/hotplug-pci.c
> > @@ -6,13 +6,21 @@
> >  
> >  unsigned int __devinit pci_do_scan_bus(struct pci_bus *bus)
> >  {
> > -	unsigned int max;
> > +	unsigned int max, pass;
> > +	struct pci_dev *dev;
> >  
> >  	max = pci_scan_child_bus(bus);
> >  
> > -	/*
> > -	 * Make the discovered devices available.
> > -	 */
> > +	for (pass=0; pass < 2; pass++)
> > +		list_for_each_entry(dev, &bus->devices, bus_list) {
> > +			if (dev->hdr_type == PCI_HEADER_TYPE_BRIDGE ||
> > +			    dev->hdr_type == PCI_HEADER_TYPE_CARDBUS)
> > +				if (pass && dev->subordinate)
> > +					pci_bus_size_bridges(dev->subordinate);
> > +		}
> > +
> > +	pci_bus_assign_resources(bus);
> > +	pci_enable_bridges(bus);
> >  	pci_bus_add_devices(bus);
> 
> The "for (pass=0; pass <2; pass++)" loop doesn't look necessary.

Yes, I don't know why I had it in there originally. I can remove
that.

> And I'm worrying that your change have some bad effect to the
> existing user of pci_do_scan_bus(). Did you confirm that?

I hadn't gotten around to verifying/fixing existing callers of
pci_do_scan_bus yet. I was focusing on the core first.

There aren't too many callers, but unfortunately, I don't have
any hardware that actually uses the existing drivers.

I seem to recall that your machines support shpchp. Would you
mind testing this patch and telling me if your machine still
behaves properly?

I looked at shpchp_configure_device and I think that simply
scanning the device's parent bus should work.

Thanks.

/ac

diff --git a/drivers/pci/hotplug/shpchp_pci.c b/drivers/pci/hotplug/shpchp_pci.c
index aa315e5..7e8457b 100644
--- a/drivers/pci/hotplug/shpchp_pci.c
+++ b/drivers/pci/hotplug/shpchp_pci.c
@@ -110,11 +110,7 @@ int __ref shpchp_configure_device(struct slot *p_slot)
 		return -EINVAL;
 	}
 
-	num = pci_scan_slot(parent, PCI_DEVFN(p_slot->device, 0));
-	if (num == 0) {
-		ctrl_err(ctrl, "No new device found\n");
-		return -ENODEV;
-	}
+	pci_do_scan_bus(parent);
 
 	for (fn = 0; fn < 8; fn++) {
 		dev = pci_get_slot(parent, PCI_DEVFN(p_slot->device, fn));
@@ -126,40 +122,10 @@ int __ref shpchp_configure_device(struct slot *p_slot)
 			pci_dev_put(dev);
 			continue;
 		}
-		if ((dev->hdr_type == PCI_HEADER_TYPE_BRIDGE) ||
-				(dev->hdr_type == PCI_HEADER_TYPE_CARDBUS)) {
-			/* Find an unused bus number for the new bridge */
-			struct pci_bus *child;
-			unsigned char busnr, start = parent->secondary;
-			unsigned char end = parent->subordinate;
-			for (busnr = start; busnr <= end; busnr++) {
-				if (!pci_find_bus(pci_domain_nr(parent),
-							busnr))
-					break;
-			}
-			if (busnr > end) {
-				ctrl_err(ctrl,
-					 "No free bus for hot-added bridge\n");
-				pci_dev_put(dev);
-				continue;
-			}
-			child = pci_add_new_bus(parent, dev, busnr);
-			if (!child) {
-				ctrl_err(ctrl, "Cannot add new bus for %s\n",
-					 pci_name(dev));
-				pci_dev_put(dev);
-				continue;
-			}
-			child->subordinate = pci_do_scan_bus(child);
-			pci_bus_size_bridges(child);
-		}
 		program_fw_provided_values(dev);
 		pci_dev_put(dev);
 	}
 
-	pci_bus_assign_resources(parent);
-	pci_bus_add_devices(parent);
-	pci_enable_bridges(parent);
 	return 0;
 }
 
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