From: Hongyu Xie <xiehongyu1@xxxxxxxxxx>
Hi Alan,
On 2024/9/12 23:00, Alan Stern wrote:
On Thu, Sep 12, 2024 at 11:21:26AM +0800, duanchenghao wrote:
在 2024-09-11星期三的 10:40 -0400，Alan Stern写道：
On Tue, Sep 10, 2024 at 05:36:56PM +0800, duanchenghao wrote:
S4 wakeup restores the image that was saved before the system
entered
the S4 sleep state.
S4 waking up from hibernation
=============================
kernel initialization
|
v
freeze user task and kernel thread
|
v
load saved image
|
v
freeze the peripheral device and controller
(Check the HCD_FLAG_WAKEUP_ PENDING flag of the USB. If it is
set,
return to EBUSY and do not perform the following restore
image.)
Why is the flag set at this point? It should not be; the device and
controller should have been frozen with wakeup disabled.
This is check point, not set point.
Yes, I know that. But when the flag was checked, why did the code find
that it was set? The flag should have been clear.
Maybe duanchenghao means this,
freeze_kernel_threads
load_image_and_restore
suspend roothub
interrupt occurred
usb_hcd_resume_root_hub
set HCD_FLAG_WAKEUP_PENDING
queue_work // freezed
suspend pci
return -EBUSY because HCD_FLAG_WAKEUP_PENDING
So s4 resume failed.
Is your problem related to the one discussed in this email thread?
https://lore.kernel.org/linux-usb/d8600868-6e4b-45ab-b328-852b6ac8ecb5@xxxxxxxxxxxxxxxxxxx/
Would the suggestion I made there -- i.e., have the xhci-hcd
interrupt handler skip calling usb_hcd_resume_root_hub() if the root
hub
was suspended with wakeup = 0 -- fix your problem?
Skipping usb_hcd_resume_root_hub() should generally be possible, but
it's important to ensure that normal remote wakeup functionality is not
compromised. Is it HUB_SUSPEND that the hub you are referring to is in
a suspended state?
I don't understand this question. hub_quiesce() gets called with
HUB_SUSPEND when the hub enters a suspended state.
You are correct about the need for normal remote wakeup to work
properly. The interrupt handler should skip calling
usb_hcd_resume_root_hub() for port connect or disconnect changes and for
port overcurrent changes (when the root hub is suspended with wakeup =
0). But it should _not_ skip calling usb_hcd_resume_root_hub() for port
resume events.
Alan Stern
Hongyu Xie
