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SubjectRe: [PATCH] usb: host: xhci: Avoid XHCI resume delay if SSUSB device is not present
On 27.4.2023 22.01, Wesley Cheng wrote:
> There is a 120ms delay implemented for allowing the XHCI host controller to
> detect a U3 wakeup pulse. The intention is to wait for the device to retry
> the wakeup event if the USB3 PORTSC doesn't reflect the RESUME link status
> by the time it is checked. As per the USB3 specification:
>
> tU3WakeupRetryDelay ("Table 7-12. LTSSM State Transition Timeouts")
>
> This would allow the XHCI resume sequence to determine if the root hub
> needs to be also resumed. However, in case there is no device connected,
> or if there is only a HSUSB device connected, this delay would still affect
> the overall resume timing.
>
> Since this delay is solely for detecting U3 wake events (USB3 specific)
> then ignore this delay for the disconnected case and the HSUSB connected
> only case.
>
> Signed-off-by: Wesley Cheng <quic_wcheng@quicinc.com>
> ---
> drivers/usb/host/xhci.c | 6 +++++-
> 1 file changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/usb/host/xhci.c b/drivers/usb/host/xhci.c
> index 78790dc13c5f..7a86cd683502 100644
> --- a/drivers/usb/host/xhci.c
> +++ b/drivers/usb/host/xhci.c
> @@ -834,7 +834,8 @@ static bool xhci_pending_portevent(struct xhci_hcd *xhci)
> while (port_index--) {
> portsc = readl(ports[port_index]->addr);
> if (portsc & PORT_CHANGE_MASK ||
> - (portsc & PORT_PLS_MASK) == XDEV_RESUME)
> + (portsc & PORT_PLS_MASK) == XDEV_RESUME ||
> + !(portsc & PORT_CONNECT))
> return true;
This change will report a pending port event at the first empty roothub port.

I think we are looking for something like this instead (pseudo):

@@ -1116,7 +1116,7 @@ int xhci_resume(struct xhci_hcd *xhci, bool hibernated)
* the first wake signalling failed, give it that chance.
*/
pending_portevent = xhci_pending_portevent(xhci);
- if (!pending_portevent) {
+ if (!pending_portevent && usb3_devices_connected && runtime_resume) {
msleep(120);
pending_portevent = xhci_pending_portevent(xhci);
}

Thanks
Mathias

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