From patchwork Wed May 29 10:49:42 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Mika Westerberg X-Patchwork-Id: 10966775 X-Patchwork-Delegate: bhelgaas@google.com Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id DAC06933 for ; Wed, 29 May 2019 10:49:46 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id C807E287E9 for ; Wed, 29 May 2019 10:49:46 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id B7D5728874; Wed, 29 May 2019 10:49:46 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.9 required=2.0 tests=BAYES_00,MAILING_LIST_MULTI, RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 38524287E9 for ; Wed, 29 May 2019 10:49:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725914AbfE2Ktp (ORCPT ); Wed, 29 May 2019 06:49:45 -0400 Received: from mga11.intel.com ([192.55.52.93]:55874 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725894AbfE2Ktp (ORCPT ); Wed, 29 May 2019 06:49:45 -0400 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga007.fm.intel.com ([10.253.24.52]) by fmsmga102.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 29 May 2019 03:49:44 -0700 X-ExtLoop1: 1 Received: from black.fi.intel.com ([10.237.72.28]) by fmsmga007.fm.intel.com with ESMTP; 29 May 2019 03:49:43 -0700 Received: by black.fi.intel.com (Postfix, from userid 1001) id 9C2CA12C; Wed, 29 May 2019 13:49:42 +0300 (EEST) From: Mika Westerberg To: Bjorn Helgaas Cc: Logan Gunthorpe , Mika Westerberg , linux-pci@vger.kernel.org Subject: [PATCH] PCI: Add sysfs attribute for disabling PCIe link to downstream component Date: Wed, 29 May 2019 13:49:42 +0300 Message-Id: <20190529104942.74991-1-mika.westerberg@linux.intel.com> X-Mailer: git-send-email 2.20.1 MIME-Version: 1.0 Sender: linux-pci-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP PCIe root and downstream ports have link control register that can be used disable the link from software. This can be useful for instance when performing "software" hotplug on systems that do not support real PCIe/ACPI hotplug. For example when used with FPGA card we can burn a new FPGA image without need to reboot the system. First we remove the FGPA device from Linux PCI stack: # echo 1 > /sys/bus/pci/devices/0000:00:01.1/0000:02:00.0/remove Then we disable the link: # echo 1 > /sys/bus/pci/devices/0000:00:01.1/link_disable By doing this we prevent the kernel from accessing the hardware while we burn the new FPGA image. Once the new FPGA is burned we can re-enable the link and rescan the new and possibly different device: # echo 0 > /sys/bus/pci/devices/0000:00:01.1/link_disable # echo 1 > /sys/bus/pci/devices/0000:00:01.1/rescan Signed-off-by: Mika Westerberg --- Documentation/ABI/testing/sysfs-bus-pci | 8 +++ drivers/pci/pci-sysfs.c | 65 ++++++++++++++++++++++++- 2 files changed, 72 insertions(+), 1 deletion(-) diff --git a/Documentation/ABI/testing/sysfs-bus-pci b/Documentation/ABI/testing/sysfs-bus-pci index 8bfee557e50e..c93d6b9ab580 100644 --- a/Documentation/ABI/testing/sysfs-bus-pci +++ b/Documentation/ABI/testing/sysfs-bus-pci @@ -324,6 +324,14 @@ Description: This is similar to /sys/bus/pci/drivers_autoprobe, but affects only the VFs associated with a specific PF. +What: /sys/bus/pci/devices/.../link_disable +Date: September 2019 +Contact: Mika Westerberg +Description: + PCIe root and downstream ports have this attribute. Writing + 1 causes the link to downstream component be disabled. + Re-enabling the link happens by writing 0 instead. + What: /sys/bus/pci/devices/.../p2pmem/size Date: November 2017 Contact: Logan Gunthorpe diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c index 6d27475e39b2..dfcd21745192 100644 --- a/drivers/pci/pci-sysfs.c +++ b/drivers/pci/pci-sysfs.c @@ -218,6 +218,56 @@ static ssize_t current_link_width_show(struct device *dev, } static DEVICE_ATTR_RO(current_link_width); +static ssize_t link_disable_show(struct device *dev, + struct device_attribute *attr, char *buf) +{ + struct pci_dev *pci_dev = to_pci_dev(dev); + u16 linkctl; + int ret; + + ret = pcie_capability_read_word(pci_dev, PCI_EXP_LNKCTL, &linkctl); + if (ret) + return -EINVAL; + + return sprintf(buf, "%d\n", !!(linkctl & PCI_EXP_LNKCTL_LD)); +} + +static ssize_t link_disable_store(struct device *dev, + struct device_attribute *attr, + const char *buf, size_t count) +{ + struct pci_dev *pci_dev = to_pci_dev(dev); + u16 linkctl; + bool disable; + int ret; + + ret = kstrtobool(buf, &disable); + if (ret) + return ret; + + ret = pcie_capability_read_word(pci_dev, PCI_EXP_LNKCTL, &linkctl); + if (ret) + return -EINVAL; + + if (disable) { + if (linkctl & PCI_EXP_LNKCTL_LD) + goto out; + linkctl |= PCI_EXP_LNKCTL_LD; + } else { + if (!(linkctl & PCI_EXP_LNKCTL_LD)) + goto out; + linkctl &= ~PCI_EXP_LNKCTL_LD; + } + + ret = pcie_capability_write_word(pci_dev, PCI_EXP_LNKCTL, linkctl); + if (ret) + return ret; + +out: + return count; +} +static DEVICE_ATTR_RW(link_disable); + static ssize_t secondary_bus_number_show(struct device *dev, struct device_attribute *attr, char *buf) @@ -785,6 +835,7 @@ static struct attribute *pcie_dev_attrs[] = { &dev_attr_current_link_width.attr, &dev_attr_max_link_width.attr, &dev_attr_max_link_speed.attr, + &dev_attr_link_disable.attr, NULL, }; @@ -1656,8 +1707,20 @@ static umode_t pcie_dev_attrs_are_visible(struct kobject *kobj, struct device *dev = kobj_to_dev(kobj); struct pci_dev *pdev = to_pci_dev(dev); - if (pci_is_pcie(pdev)) + if (pci_is_pcie(pdev)) { + if (a == &dev_attr_link_disable.attr) { + switch (pci_pcie_type(pdev)) { + case PCI_EXP_TYPE_ROOT_PORT: + case PCI_EXP_TYPE_DOWNSTREAM: + break; + + default: + return 0; + } + } + return a->mode; + } return 0; }