From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qt0-f193.google.com ([209.85.216.193]:43407 "EHLO mail-qt0-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751718AbeFEM1P (ORCPT ); Tue, 5 Jun 2018 08:27:15 -0400 MIME-Version: 1.0 In-Reply-To: <20180604155523.14906-1-mr.nuke.me@gmail.com> References: <20180604155523.14906-1-mr.nuke.me@gmail.com> From: Andy Shevchenko Date: Tue, 5 Jun 2018 15:27:14 +0300 Message-ID: Subject: Re: [PATCH v3] PCI: Check for PCIe downtraining conditions To: Alexandru Gagniuc Cc: Bjorn Helgaas , alex_gagniuc@dellteam.com, austin_bolen@dell.com, shyam_iyer@dell.com, Keith Busch , linux-pci@vger.kernel.org, Linux Kernel Mailing List Content-Type: text/plain; charset="UTF-8" Sender: linux-pci-owner@vger.kernel.org List-ID: On Mon, Jun 4, 2018 at 6:55 PM, Alexandru Gagniuc wrote: > PCIe downtraining happens when both the device and PCIe port are > capable of a larger bus width or higher speed than negotiated. > Downtraining might be indicative of other problems in the system, and > identifying this from userspace is neither intuitive, nor straigh > forward. > > The easiest way to detect this is with pcie_print_link_status(), > since the bottleneck is usually the link that is downtrained. It's not > a perfect solution, but it works extremely well in most cases. Have you seen any of my comments? For your convenience repeating below. > > Signed-off-by: Alexandru Gagniuc > --- > > Changes since v2: > - Check dev->is_virtfn flag > > Changes since v1: > - Use pcie_print_link_status() instead of reimplementing logic > > drivers/pci/probe.c | 22 ++++++++++++++++++++++ > 1 file changed, 22 insertions(+) > > diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c > index ac91b6fd0bcd..a88ec8c25dd5 100644 > --- a/drivers/pci/probe.c > +++ b/drivers/pci/probe.c > @@ -2146,6 +2146,25 @@ static struct pci_dev *pci_scan_device(struct pci_bus *bus, int devfn) > return dev; > } > > +static void pcie_check_upstream_link(struct pci_dev *dev) > +{ > + This is redundant blank line. > + if (!pci_is_pcie(dev)) > + return; > + > + /* Look from the device up to avoid downstream ports with no devices. */ > + if ((pci_pcie_type(dev) != PCI_EXP_TYPE_ENDPOINT) && > + (pci_pcie_type(dev) != PCI_EXP_TYPE_LEG_END) && > + (pci_pcie_type(dev) != PCI_EXP_TYPE_UPSTREAM)) > + return; I looked briefly at the use of these calls and perhaps it might make sense to introduce pci_is_pcie_type(dev, type) which unifies pci_is_pcie() + pci_pcie_type(). > + > + /* Multi-function PCIe share the same link/status. */ > + if ((PCI_FUNC(dev->devfn) != 0) || dev->is_virtfn) The one pair of parens is not needed. > + return; > + > + pcie_print_link_status(dev); > +} > + > static void pci_init_capabilities(struct pci_dev *dev) > { > /* Enhanced Allocation */ > @@ -2181,6 +2200,9 @@ static void pci_init_capabilities(struct pci_dev *dev) > /* Advanced Error Reporting */ > pci_aer_init(dev); > > + /* Check link and detect downtrain errors */ > + pcie_check_upstream_link(dev); > + > if (pci_probe_reset_function(dev) == 0) > dev->reset_fn = 1; > } > -- > 2.14.4 > -- With Best Regards, Andy Shevchenko