linux-kernel - [PATCH v2 2/8] USB / PCI / PM: Allow the PCI core to do the resume cleanup

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Date:   Mon, 12 Jun 2017 22:49:40 +0200
From:   "Rafael J. Wysocki" <rjw@...ysocki.net>
To:     Linux ACPI <linux-acpi@...r.kernel.org>
Cc:     Linux PCI <linux-pci@...r.kernel.org>,
        Linux PM <linux-pm@...r.kernel.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Mika Westerberg <mika.westerberg@...ux.intel.com>,
        Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
        Linux USB <linux-usb@...r.kernel.org>,
        Mathias Nyman <mathias.nyman@...ux.intel.com>,
        Felipe Balbi <balbi@...nel.org>,
        Mario Limonciello <mario_limonciello@...l.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Dominik Brodowski <linux@...inikbrodowski.net>,
        Hans De Goede <hdegoede@...hat.com>,
        Alan Stern <stern@...land.harvard.edu>
Subject: [PATCH v2 2/8] USB / PCI / PM: Allow the PCI core to do the resume cleanup

From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>

hcd_pci_resume_noirq() used as a universal _resume_noirq handler for
PCI USB controllers calls pci_back_from_sleep() which is unnecessary
and may become problematic.

It is unnecessary, because the PCI bus type carries out post-suspend
cleanup of all PCI devices during resume and that covers all things
done by the pci_back_from_sleep().  There is no reason why USB cannot
follow all of the other PCI devices in that respect.

It will become problematic after subsequent changes that make it
possible to go back to sleep again after executing dpm_resume_noirq()
if no valid system wakeup events have been detected at that point.
Namely, calling pci_back_from_sleep() at the _resume_noirq stage
will cause the wakeup status of the devices in question to be cleared
and if any of them has triggered system wakeup, that event may be
missed then.

For the above reasons, drop the pci_back_from_sleep() invocation
from hcd_pci_resume_noirq().

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
Acked-by: Alan Stern <stern@...land.harvard.edu>
---
 drivers/usb/core/hcd-pci.c |    7 +------
 1 file changed, 1 insertion(+), 6 deletions(-)

Index: linux-pm/drivers/usb/core/hcd-pci.c
===================================================================
--- linux-pm.orig/drivers/usb/core/hcd-pci.c
+++ linux-pm/drivers/usb/core/hcd-pci.c
@@ -584,12 +584,7 @@ static int hcd_pci_suspend_noirq(struct

 static int hcd_pci_resume_noirq(struct device *dev)
 {
-	struct pci_dev		*pci_dev = to_pci_dev(dev);
-
-	powermac_set_asic(pci_dev, 1);
-
-	/* Go back to D0 and disable remote wakeup */
-	pci_back_from_sleep(pci_dev);
+	powermac_set_asic(to_pci_dev(dev), 1);
 	return 0;
 }