Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752136AbbHNU0p (ORCPT ); Fri, 14 Aug 2015 16:26:45 -0400 Received: from mail-wi0-f169.google.com ([209.85.212.169]:36991 "EHLO mail-wi0-f169.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751443AbbHNU0m (ORCPT ); Fri, 14 Aug 2015 16:26:42 -0400 MIME-Version: 1.0 In-Reply-To: <20150814164324.GC22809@arm.com> References: <1439569159-10051-1-git-send-email-marc.zyngier@arm.com> <1439569159-10051-3-git-send-email-marc.zyngier@arm.com> <20150814164051.GF26431@google.com> <20150814164324.GC22809@arm.com> From: Bjorn Helgaas Date: Fri, 14 Aug 2015 15:26:21 -0500 Message-ID: Subject: Re: [PATCH v2 2/4] PCI: pci-host-generic: Fix lookup of linux,pci-probe-only property To: Will Deacon Cc: Marc Zyngier , Benjamin Herrenschmidt , Paul Mackerras , Michael Ellerman , "suravee.suthikulpanit@amd.com" , Lorenzo Pieralisi , "grant.likely@linaro.org" , Rob Herring , "agraf@suse.de" , "linux-kernel@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" , "linuxppc-dev@lists.ozlabs.org" , "linux-pci@vger.kernel.org" , "devicetree@vger.kernel.org" Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3303 Lines: 77 On Fri, Aug 14, 2015 at 11:43 AM, Will Deacon wrote: > On Fri, Aug 14, 2015 at 05:40:51PM +0100, Bjorn Helgaas wrote: >> 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 >> > --- >> > 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.) > > Kvmtool certainly uses it (and generates its own DT, hence why you don't > see it in mainline). Not sure about qemu, though. Do you know why kvmtool wants probe-only? Would something break if we didn't support probe-only? I guess we'd be looking for a case where Linux assigns resources and that assignment doesn't work with kvmtool? "pci-probe-only" doesn't appear in qemu (git://git.qemu-project.org/qemu.git). (I guess Alexander confirmed that later.) Alexander wrote: > QEMU definitely doesn't do proble-only. > Is this driver used on real PPC machines too? I think you're asking about pci-host-generic.c, and the answer is "no," because pci-host-generic.c currently depends on CONFIG_ARM. Bjorn -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/