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

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Message-Id: <20220407115918.1.I8226c7fdae88329ef70957b96a39b346c69a914e@changeid>
Date:   Thu,  7 Apr 2022 11:59:55 -0700
From:   Evan Green <evgreen@...omium.org>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Rajat Jain <rajatja@...omium.org>,
        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] 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 fails to recover.

Signed-off-by: Evan Green <evgreen@...omium.org>
---

You may be able to reproduce this issue on your own machine via the
following:
1. Disable runtime PM on your XHCI controller
2. Aim your XHCI IRQ at a non-boot CPU (replace 174): echo 2 >
   /proc/irq/174/smp_affinity
3. Attempt to hibernate (no need to actually go all the way down).

I run 2 and 3 in a loop, and can usually hit a hang or dead XHCI
controller within 1-2 iterations. I happened to notice this on an
Alderlake system where runtime PM is accidentally disabled for one of
the XHCI controllers. Some more discussion and debugging can be found at
[1].

[1] https://lore.kernel.org/linux-pci/CAE=gft4a-QL82iFJE_xRQ3JrMmz-KZKWREtz=MghhjFbJeK=8A@mail.gmail.com/T/#u

---
 drivers/usb/core/hcd-pci.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/usb/core/hcd-pci.c b/drivers/usb/core/hcd-pci.c
index 8176bc81a635d6..e02506807ffc6c 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_noirq	= check_root_hub_suspended,
-	.thaw_noirq	= NULL,
-	.thaw		= NULL,
+	.freeze		= hcd_pci_suspend,
+	.freeze_noirq	= hcd_pci_suspend_noirq,
+	.thaw_noirq	= hcd_pci_resume_noirq,
+	.thaw		= hcd_pci_resume,
 	.poweroff	= hcd_pci_suspend,
 	.poweroff_noirq	= hcd_pci_suspend_noirq,
 	.restore_noirq	= hcd_pci_resume_noirq,
-- 
2.31.0