From patchwork Fri Sep 25 10:23:06 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Yicong Yang X-Patchwork-Id: 11799491 X-Patchwork-Delegate: bhelgaas@google.com Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id E56DF6CB for ; Fri, 25 Sep 2020 10:24:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id CE502221EB for ; Fri, 25 Sep 2020 10:24:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727520AbgIYKYd (ORCPT ); Fri, 25 Sep 2020 06:24:33 -0400 Received: from szxga07-in.huawei.com ([45.249.212.35]:44332 "EHLO huawei.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1727132AbgIYKYc (ORCPT ); Fri, 25 Sep 2020 06:24:32 -0400 Received: from DGGEMS402-HUB.china.huawei.com (unknown [172.30.72.58]) by Forcepoint Email with ESMTP id D2E28640E55D0B9C83BF; Fri, 25 Sep 2020 18:24:30 +0800 (CST) Received: from localhost.localdomain (10.67.165.24) by DGGEMS402-HUB.china.huawei.com (10.3.19.202) with Microsoft SMTP Server id 14.3.487.0; Fri, 25 Sep 2020 18:24:20 +0800 From: Yicong Yang To: , CC: , , , , Subject: [PATCH v2] PCI: Make sure the bus bridge powered on when scanning bus Date: Fri, 25 Sep 2020 18:23:06 +0800 Message-ID: <1601029386-4928-1-git-send-email-yangyicong@hisilicon.com> X-Mailer: git-send-email 2.8.1 MIME-Version: 1.0 X-Originating-IP: [10.67.165.24] X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org When the bus bridge is runtime suspended, we'll fail to rescan the devices through sysfs as we cannot access the configuration space correctly when the bridge is in D3hot. It can be reproduced like: $ echo 1 > /sys/bus/pci/devices/0000:80:00.0/0000:81:00.1/remove $ echo 1 > /sys/bus/pci/devices/0000:80:00.0/pci_bus/0000:81/rescan 0000:80:00.0 is root port and is runtime suspended and we cannot get 0000:81:00.1 after rescan. Make bridge powered on when scanning the child bus, by adding pm_runtime_get_sync()/pm_runtime_put() in pci_scan_child_bus_extend(). A similar issue is met and solved by commit d963f6512e15 ("PCI: Power on bridges before scanning new devices") which rescan the devices through /sys/bus/pci/devices/0000:80:00.0/rescan. The callstack is like: dev_rescan_restore() pci_rescan_bus() pci_scan_bridge_extend() pci_scan_child_bus_extend() /* will wake up the bridge with this patch */ With this patch the issue is also resolved, so let's remove the calls of pm_runtime_*() in pci_scan_bridge_extend(). Signed-off-by: Yicong Yang --- Change since v1: - use an intermediate variable *bridge as suggested - remove the pm_runtime_*() calls in pci_scan_bridge_extend() drivers/pci/probe.c | 21 ++++++++++++--------- 1 file changed, 12 insertions(+), 9 deletions(-) -- 2.8.1 diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c index 03d3712..747a8bc 100644 --- a/drivers/pci/probe.c +++ b/drivers/pci/probe.c @@ -1211,12 +1211,6 @@ static int pci_scan_bridge_extend(struct pci_bus *bus, struct pci_dev *dev, u8 fixed_sec, fixed_sub; int next_busnr; - /* - * Make sure the bridge is powered on to be able to access config - * space of devices below it. - */ - pm_runtime_get_sync(&dev->dev); - pci_read_config_dword(dev, PCI_PRIMARY_BUS, &buses); primary = buses & 0xFF; secondary = (buses >> 8) & 0xFF; @@ -1418,8 +1412,6 @@ static int pci_scan_bridge_extend(struct pci_bus *bus, struct pci_dev *dev, out: pci_write_config_word(dev, PCI_BRIDGE_CONTROL, bctl); - pm_runtime_put(&dev->dev); - return max; } @@ -2796,11 +2788,19 @@ static unsigned int pci_scan_child_bus_extend(struct pci_bus *bus, unsigned int used_buses, normal_bridges = 0, hotplug_bridges = 0; unsigned int start = bus->busn_res.start; unsigned int devfn, fn, cmax, max = start; - struct pci_dev *dev; + struct pci_dev *dev, *bridge = bus->self; int nr_devs; dev_dbg(&bus->dev, "scanning bus\n"); + /* + * Make sure the bus bridge is powered on, otherwise we may not be + * able to scan the devices as we may fail to access the configuration + * space of subordinates. + */ + if (bridge) + pm_runtime_get_sync(&bridge->dev); + /* Go find them, Rover! */ for (devfn = 0; devfn < 256; devfn += 8) { nr_devs = pci_scan_slot(bus, devfn); @@ -2913,6 +2913,9 @@ static unsigned int pci_scan_child_bus_extend(struct pci_bus *bus, } } + if (bridge) + pm_runtime_put(&bridge->dev); + /* * We've scanned the bus and so we know all about what's on * the other side of any bridges that may be on this bus plus