Hi Mathias,
On 4/25/2023 2:04 AM, Mathias Nyman wrote:
On 25.4.2023 3.09, Wesley Cheng wrote:
Hi Mathias,
On 4/24/2023 8:05 AM, Mathias Nyman wrote:
On 21.4.2023 7.58, Basavaraj Natikar wrote:
On 4/20/2023 10:33 PM, Mark Hasemeyer wrote:
It may be necessary to wait only for auto-resume cases.
I find this comment misleading as the patch assumes that it's only
necessary to
wait for auto-resume cases. Are there any cases where the driver
should wait
during system-resume?
Only in case of auto-resume (runtime resume).
Rewording the commit message as follows.
Thanks for fixing this extra system resume delay
Maybe some kind of big picture explanation could be added to the
commit message,
such as:
Avoid extra 120ms delay during system resume.
xHC controller may signal wake up to 120ms before it shows which USB
device
caused the wake on the xHC port registers.
The xhci driver therefore checks for port activity up to 120ms during
resume,
making sure that the hub driver can see the port change, and won't
immediately
runtime suspend back due to no port activity.
This is however only needed for runtime resume as system resume will
resume
all child hubs and other child usb devices anyway.
Each XHCI controller while xhci_resumes by default takes 120 ms more if
there is no activity on the ports or no ports connected. Therefore, if
there are more USB controllers on the system, 120 ms more per
controller
will add delay to system resume from suspended states like s2idle,
S3 or
S4 states.
Once the XHCI controller is in runtime suspended state (D3 state),
on USB
device hotplug controller will runtime resume (D0 state) and check for
pending port events if no events, wait for 120 ms to re-check for port
activity to handle missed wake signal.
A delay of 120 ms more to re-check for port activity is needed only in
auto-resume (runtime resume) cases. Hence, add a check only for runtime
resume from runtime suspend (D3->D0) to avoid the 120ms more delay for
other PM events (system resume from suspend states like s2idle, S3
or S4
states) so that the system resume time can be improved.
Please let me know if any inputs.
I can only think of one minor side-effect that would be runtime
suspending back
too early after system resume. This could happen when connecting the
first
usb device to a roothub on a (system) suspended setup?
steps:
1. in system suspend, no usb devices connected, xhci in D3, can
signal wake with PME#
2. connect first usb device, xHC signals PME# wake
3. system resumes, xhci resumes to D0, but no actity visible on xHC
port registers
Thanks for bringing up this topic Basavaraj.
Sorry for jumping into this thread, but was looking to optimize this
resume timing as well, since it is affecting some of the host driven
bus resume situations. Just had a quick question about where the
120ms delay is required...
From what I'm gathering from the USB3 spec, the 120ms timeout is the
recommended time for tU3WakeupRetryDelay ("Table 7-12. LTSSM State
Transition Timeouts"). This is the retry time that the device will
wait before re-issuing another (potential) LFPS U3 wake.
My idea was to see if we could limit this delay only for when a SSUSB
device is already connected to the root hub. (ignore if HSUSB device
connected) We would be able to eliminate the delay for:
1. No device connected to root hub
2. Only HSUSB device connected
Is that a possibility we can add on top of what Basavaraj is adding?
Sounds reasonable,
Yes the 120ms was intended for the U3 wake delay for SuperSpeed devices.
We should probably also check for CAS bit in xhci_pending_portevent()
(I'll add that CAS check)
Thanks for the info. I'll make a change to add the checks I mentioned
above and submit it as a separate patch for review.
Thanks
Wesley Cheng
