From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx1.redhat.com ([209.132.183.28]:65343 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932121Ab2GKSpG (ORCPT ); Wed, 11 Jul 2012 14:45:06 -0400 Date: Wed, 11 Jul 2012 13:14:58 -0400 From: Jason Baron To: Bjorn Helgaas Cc: Yinghai Lu , linux-pci@vger.kernel.org Subject: Re: [PATCH 4/5] PCI, acpiphp: add is_hotplug_bridge detection Message-ID: <20120711171458.GA14610@redhat.com> References: <1340437325-29282-1-git-send-email-yinghai@kernel.org> <1340437325-29282-5-git-send-email-yinghai@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: Sender: linux-pci-owner@vger.kernel.org List-ID: On Wed, Jul 11, 2012 at 09:50:19AM -0600, Bjorn Helgaas wrote: > On Sat, Jun 23, 2012 at 1:42 AM, Yinghai Lu wrote: > > When system support hotplug bridge with children hotplug slots, we need to make sure > > that parent bridge get preallocated resource so later when device is plugged into > > children slot, those children devices will get resource allocated. > > > > We do not meet this problem, because for pcie hotplug card, when acpiphp is used, > > pci_scan_bridge will set that for us when detect hotplug bit in slot cap. > > > > Reported-and-tested-by: Jason Baron > > Signed-off-by: Yinghai Lu > > Acked-by: Jason Baron > > --- > > drivers/pci/hotplug/acpiphp_glue.c | 27 ++++++++++++++++++++++++++- > > 1 files changed, 26 insertions(+), 1 deletions(-) > > > > diff --git a/drivers/pci/hotplug/acpiphp_glue.c b/drivers/pci/hotplug/acpiphp_glue.c > > index ad6fd66..0f2b72d 100644 > > --- a/drivers/pci/hotplug/acpiphp_glue.c > > +++ b/drivers/pci/hotplug/acpiphp_glue.c > > @@ -783,6 +783,29 @@ static void acpiphp_set_acpi_region(struct acpiphp_slot *slot) > > } > > } > > > > +static void check_hotplug_bridge(struct acpiphp_slot *slot, struct pci_dev *dev) > > +{ > > + struct acpiphp_func *func; > > + > > + if (!dev->subordinate) > > + return; > > + > > + /* quirk, or pcie could set it already */ > > + if (dev->is_hotplug_bridge) > > + return; > > + > > + if (PCI_SLOT(dev->devfn) != slot->device) > > + return; > > + > > + list_for_each_entry(func, &slot->funcs, sibling) { > > + if (PCI_FUNC(dev->devfn) == func->function) { > > + /* check if this bridge has ejectable slots */ > > + if ((detect_ejectable_slots(func->handle) > 0)) > > + dev->is_hotplug_bridge = 1; > > + break; > > + } > > + } > > +} > > /** > > * enable_device - enable, configure a slot > > * @slot: slot to be enabled > > @@ -817,8 +840,10 @@ static int __ref enable_device(struct acpiphp_slot *slot) > > if (dev->hdr_type == PCI_HEADER_TYPE_BRIDGE || > > dev->hdr_type == PCI_HEADER_TYPE_CARDBUS) { > > max = pci_scan_bridge(bus, dev, max, pass); > > - if (pass && dev->subordinate) > > + if (pass && dev->subordinate) { > > + check_hotplug_bridge(slot, dev); > > I don't like this patch because it increases the differences between > the hotplug drivers, rather than decreasing them. > > For PCI Express devices, we set dev->is_hotplug_bridge in the > pci_setup_device() path (in set_pcie_hotplug_bridge()). I think it > would make sense to try to expand that path to also handle SHPC and > ACPI hotplug as well. ACPI is harder because it's not PCI-specified, > so we'd need some sort of pcibios or other optional hook. > > I don't have a clear picture of how this works -- if I understand > correctly, the situation is that we have a bridge managed by acpiphp. > That part makes sense because the bridge is on the motherboard and can > have a DSDT device. Now we plug something into the slot below the > bridge. I *think* this patch handles the case where this new > hot-added thing is also a bridge managed by acpiphp. But where does > the ACPI device for this hot-added bridge come from? It's an > arbitrary device the BIOS knows nothing about, so it can't be in the > DSDT. > So this came up while I was developing pci bridge hotplug for qemu. Currently, there is a top level host bus (with ACPI device definitions), where devices can be hot-plugged. What I've done is added a second level of hotplug pci busses (again with ACPI device definitions). Thus, we can now hotplug a bridge into the top-level bus and then devices behind it. Effectively increasing the hot-plug space from n -> n^2. Before the above pci patch, the devices behind the bridge would not configure their PCI BARs properly, since there were no i/o, mem resources assigned to the bridge. However, with the above patch in place things work as expected. Using the same code base I was able to do acpi hotplug on Windows 7, which correctly configured the both the bridge window and devices behind it on hot-plug. So currently, the above usage pattern works on Windows 7, but not on Linux. Thanks, -Jason