linux-kernel - [PATCH v3 2/2] USB: hcd-pci: Fully suspend across freeze/thaw cycle

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Message-Id: <20220421103751.v3.2.I8226c7fdae88329ef70957b96a39b346c69a914e@changeid>
Date:   Thu, 21 Apr 2022 10:39:27 -0700
From:   Evan Green <evgreen@...omium.org>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Mathias Nyman <mathias.nyman@...el.com>,
        Alan Stern <stern@...land.harvard.edu>,
        Rajat Jain <rajatja@...omium.org>,
        Oliver Neukum <oneukum@...e.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Evan Green <evgreen@...omium.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        Youngjin Jang <yj84.jang@...sung.com>,
        linux-kernel@...r.kernel.org, linux-usb@...r.kernel.org
Subject: [PATCH v3 2/2] USB: hcd-pci: Fully suspend across freeze/thaw cycle

The documentation for the freeze() method says that it "should quiesce
the device so that it doesn't generate IRQs or DMA". The unspoken
consequence of not doing this is that MSIs aimed at non-boot CPUs may
get fully lost if they're sent during the period where the target CPU is
offline.

The current callbacks for USB HCD do not fully quiesce interrupts,
specifically on XHCI. Change to use the full suspend/resume flow for
freeze/thaw to ensure interrupts are fully quiesced. This fixes issues
where USB devices fail to thaw during hibernation because XHCI misses
its interrupt and cannot recover.

Signed-off-by: Evan Green <evgreen@...omium.org>
Acked-by: Alan Stern <stern@...land.harvard.edu>

---

(no changes since v2)

Changes in v2:
 - Removed the change to freeze_noirq/thaw_noirq

 drivers/usb/core/hcd-pci.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/usb/core/hcd-pci.c b/drivers/usb/core/hcd-pci.c
index 8176bc81a635d6..ae5e6d572376be 100644
--- a/drivers/usb/core/hcd-pci.c
+++ b/drivers/usb/core/hcd-pci.c
@@ -616,10 +616,10 @@ const struct dev_pm_ops usb_hcd_pci_pm_ops = {
 	.suspend_noirq	= hcd_pci_suspend_noirq,
 	.resume_noirq	= hcd_pci_resume_noirq,
 	.resume		= hcd_pci_resume,
-	.freeze		= check_root_hub_suspended,
+	.freeze		= hcd_pci_suspend,
 	.freeze_noirq	= check_root_hub_suspended,
 	.thaw_noirq	= NULL,
-	.thaw		= NULL,
+	.thaw		= hcd_pci_resume,
 	.poweroff	= hcd_pci_suspend,
 	.poweroff_noirq	= hcd_pci_suspend_noirq,
 	.restore_noirq	= hcd_pci_resume_noirq,
-- 
2.31.0