On Tue, 20 May 2014, Dan Williams wrote:
> Resuming a powered down port sometimes results in the port state being
> stuck in the training sequence.
>
> hub 3-0:1.0: debounce: port 1: total 2000ms stable 0ms status 0x2e0
> port1: can't get reconnection after setting port power on, status -110
> hub 3-0:1.0: port 1 status 0000.02e0 after resume, -19
> usb 3-1: can't resume, status -19
> hub 3-0:1.0: logical disconnect on port 1
>
> In the case above we wait for the port re-connect timeout of 2 seconds
> and observe that the port status is USB_SS_PORT_LS_POLLING (although it
> is likely toggling between this state and USB_SS_PORT_LS_RX_DETECT).
> This is indicative of a case where the device is failing to progress the
> link training state machine.
>
> It is resolved by issuing a warm reset to get the hub and device link
> state machines back in sync.
>
> hub 3-0:1.0: debounce: port 1: total 2000ms stable 0ms status 0x2e0
> usb usb3: port1 usb_port_runtime_resume requires warm reset
> hub 3-0:1.0: port 1 not warm reset yet, waiting 50ms
> usb 3-1: reset SuperSpeed USB device number 2 using xhci_hcd
>
> After a reconnect timeout when we expect the device to be present, force
> a warm reset of the device. Note that we can not simply look at the
> link status to determine if a warm reset is required as any of the
> training states USB_SS_PORT_LS_POLLING, USB_SS_PORT_LS_RX_DETECT, or
> USB_SS_PORT_LS_COMP_MOD are valid states that do not indicate the need
> for warm reset by themselves.
> --- a/drivers/usb/core/hub.c
> +++ b/drivers/usb/core/hub.c
> @@ -2570,10 +2570,12 @@ static int hub_port_reset(struct usb_hub *hub, int
> port1,
> /* Is a USB 3.0 port in the Inactive or Compliance Mode state?
> * Port worm reset is required to recover
> */
> -static bool hub_port_warm_reset_required(struct usb_hub *hub, u16 portstatus)
> +static bool hub_port_warm_reset_required(struct usb_hub *hub, int port1,
> + u16 portstatus)
> {
> return hub_is_superspeed(hub->hdev) &&
> - (((portstatus & USB_PORT_STAT_LINK_STATE) ==
> + (test_bit(port1, hub->warm_reset_bits) ||
> + ((portstatus & USB_PORT_STAT_LINK_STATE) ==
> USB_SS_PORT_LS_SS_INACTIVE) ||
> ((portstatus & USB_PORT_STAT_LINK_STATE) ==
> USB_SS_PORT_LS_COMP_MOD)) ;
This might be a little more clear if you separate out the tests and
remove the excess parens:
unsigned ls;
if (!hub_is_superspeed(hub->hdev))
return 0;
if (test_bit(port1, hub->warm_reset_bits))
return 1;
ls = portstatus & USB_PORT_STAT_LINK_STATE;
return ls == USB_SS_PORT_LS_SS_INACTIVE ||
ls == USB_SS_PORT_LS_COMP_MOD;
> @@ -2839,8 +2843,13 @@ static int check_port_resume_type(struct usb_device
> *udev,
> {
> struct usb_port *port_dev = hub->ports[port1 - 1];
>
> + /* Is a warm reset needed to recover the connection? */
> + if (udev->reset_resume
> + && hub_port_warm_reset_required(hub, port1, portstatus)) {
> + /* pass */;
You mustn't call hub_port_warm_reset_required when status < 0, because
then the portstatus value is undefined.
Have you tested this after turning off the device's persist_enabled
flag? Without a reset-resume, this will go through an awkward sequence
involving disabling the port. I think you still end up performing the
warm reset, but it's worth checking.
Alan Stern
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