From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.kernel.org ([198.145.29.136]:46961 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751429AbcEWUAv (ORCPT ); Mon, 23 May 2016 16:00:51 -0400 Date: Mon, 23 May 2016 15:00:42 -0500 From: Bjorn Helgaas To: Mika Westerberg Cc: Bjorn Helgaas , Peter Wu , "Rafael J. Wysocki" , Lukas Wunner , linux-pci@vger.kernel.org, linux-pm@vger.kernel.org Subject: Re: [PATCH] PCI: Power on bridges before scanning new devices Message-ID: <20160523200042.GB24375@localhost> References: <20160519231234.GB1785@al> <1463991648-85051-1-git-send-email-mika.westerberg@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <1463991648-85051-1-git-send-email-mika.westerberg@linux.intel.com> Sender: linux-pci-owner@vger.kernel.org List-ID: On Mon, May 23, 2016 at 11:20:48AM +0300, Mika Westerberg wrote: > When a PCI device is removed through sysfs interface the upstream bridge > (PCIe port) can be runtime suspended if it was the last device on that bus. > Now, if the bridge is in D3 we cannot find devices below the bridge > anymore. For example following fails to find the removed device again: > > # echo 1 > /sys/bus/pci/devices/0000:00:01.0/0000:01:00.0/remove > # echo 1 > /sys/bus/pci/devices/0000:00:01.0/rescan > > Where 0000:00:01.0 is the bridge device. > > In order to be able to rescan devices below the bridge add > pm_runtime_get_sync()/pm_runtime_put() calls to pci_scan_bridge(). This > should keep bridges powered on while their children devices are being > scanned. > > Reported-by: Peter Wu > Signed-off-by: Mika Westerberg This looks like basically the same idea as "ACPI / hotplug / PCI: Runtime resume bridge before rescan". The hotplug_event() path modified by that patch eventually calls pci_scan_bridge(): hotplug_event enable_slot pci_scan_bridge so this patch looks a little more general. Does it make "ACPI / hotplug / PCI: Runtime resume bridge before rescan" unnecessary? Can I just replace that patch with this one? > --- > drivers/pci/probe.c | 9 +++++++++ > 1 file changed, 9 insertions(+) > > diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c > index 8004f67c57ec..15e77c92311e 100644 > --- a/drivers/pci/probe.c > +++ b/drivers/pci/probe.c > @@ -16,6 +16,7 @@ > #include > #include > #include > +#include > #include "pci.h" > > #define CARDBUS_LATENCY_TIMER 176 /* secondary latency timer */ > @@ -832,6 +833,12 @@ int pci_scan_bridge(struct pci_bus *bus, struct pci_dev *dev, int max, int pass) > u8 primary, secondary, subordinate; > int broken = 0; > > + /* > + * 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; > @@ -1012,6 +1019,8 @@ int pci_scan_bridge(struct pci_bus *bus, struct pci_dev *dev, int max, int pass) > out: > pci_write_config_word(dev, PCI_BRIDGE_CONTROL, bctl); > > + pm_runtime_put(&dev->dev); > + > return max; > } > EXPORT_SYMBOL(pci_scan_bridge); > -- > 2.8.1 > > -- > To unsubscribe from this list: send the line "unsubscribe linux-pci" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html