linux-kernel - Re: [PATCH] PCI: move down pci_fixup

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Date:	Tue, 7 May 2013 15:32:50 -0600
From:	Bjorn Helgaas <bhelgaas@...gle.com>
To:	Yinghai Lu <yinghai@...nel.org>
Cc:	David Bulkow <David.Bulkow@...atus.com>, linux-pci@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] PCI: move down pci_fixup_final for hotplug path

On Thu, Apr 25, 2013 at 06:47:07PM -0700, Yinghai Lu wrote:
> David found some resource conflict issue after
> | PCI: Put pci_dev in device tree as early as possible
> | commit 4f535093cf8f6da8cfda7c36c2c1ecd2e9586ee4
> 
> and
> | USB: Fix handoff when BIOS disables host PCI device
> | commit: cab928ee1f221c9cc48d6615070fefe2e444384a
> 
> for usb qirks for hotplug path.
> 
> After checking pci_fixup_device() with pci_fixup_final,
> now we have different path for boot path and hotadd path.
> 
> Boot path: because pci_apply_fix_final_quirks is not set yet,
> 	so pci_fixup_device(pci_fixup_final) will be skipped
> 	from pci_device_add().
>         And later pci_apply_final_quirks will be called for all
> 	pci devices via fs_initcall.
> 	That is after pci_assign_unassign resource.
> 	In that case quirk could use bars with problem.
> 
> Hotadd path: pci_fixup_device(pci_fixup_final) will be executed
> 	via pci_device_add(), and that is too early for hotplug
> 	path, as pci bar for hot add devices is not assigned yet
> 	after commit 4f535093.
> 
> So we need to move down that for hotplug path, call that in
> pci_bus_add_devices instead, as at that time just before
> drivers get attached. 
> And that is simliar calling place for pci_device_add before
> commit 4f535093 is applied.
> 
> We should apply this fix for v3.9, but is too late now.
> so get it into v3.10 and could get into v3.9 stable instead.
> 
> Reported-by: David Bulkow <David.Bulkow@...atus.com>
> Tested-by: David Bulkow <David.Bulkow@...atus.com>
> Signed-off-by: Yinghai Lu <yinghai@...nel.org>

I applied the following slightly tweaked patch to for-linus and will
ask Linus to pull it for v3.10.  Let me know if it looks OK.

Bjorn

commit a939563f3fd9cd6226c7fb7135d0b93507c53888
Author: Bjorn Helgaas <bhelgaas@...gle.com>
Date:   Tue May 7 14:35:44 2013 -0600

    PCI: Delay final fixups until resources are assigned
    
    Commit 4f535093cf "PCI: Put pci_dev in device tree as early as possible"
    moved final fixups from pci_bus_add_device() to pci_device_add().  But
    pci_device_add() happens before resource assignment, so BARs may not be
    valid yet.
    
    Typical flow for hot-add:
    
        pciehp_configure_device
          pci_scan_slot
            pci_scan_single_device
              pci_device_add
                pci_fixup_device(pci_fixup_final, dev)  # previous location
          # resource assignment happens here
          pci_bus_add_devices
            pci_bus_add_device
              pci_fixup_device(pci_fixup_final, dev)    # new location
    
    [bhelgaas: changelog, move fixups to pci_bus_add_device()]
    Reference: https://lkml.kernel.org/r/20130415182614.GB9224@xanatos
    Reported-by: David Bulkow <David.Bulkow@...atus.com>
    Tested-by: David Bulkow <David.Bulkow@...atus.com>
    Signed-off-by: Yinghai Lu <yinghai@...nel.org>
    Signed-off-by: Bjorn Helgaas <bhelgaas@...gle.com>
    CC: stable@...r.kernel.org	# v3.9+

diff --git a/drivers/pci/bus.c b/drivers/pci/bus.c
index 748f8f3..32e66a6 100644
--- a/drivers/pci/bus.c
+++ b/drivers/pci/bus.c
@@ -174,6 +174,7 @@ int pci_bus_add_device(struct pci_dev *dev)
 	 * Can not put in pci_device_add yet because resources
 	 * are not assigned yet for some devices.
 	 */
+	pci_fixup_device(pci_fixup_final, dev);
 	pci_create_sysfs_dev_files(dev);
 
 	dev->match_driver = true;
diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index 43ece5d..67cd045 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -1341,7 +1341,6 @@ void pci_device_add(struct pci_dev *dev, struct pci_bus *bus)
 	list_add_tail(&dev->bus_list, &bus->devices);
 	up_write(&pci_bus_sem);
 
-	pci_fixup_device(pci_fixup_final, dev);
 	ret = pcibios_add_device(dev);
 	WARN_ON(ret < 0);
 
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