On Fri, 1 Feb 2019, Jan-Marek Glogowski wrote:
> On plug-in of my USB-C device, its USB_SS_PORT_LS_SS_INACTIVE
> link state bit is set. Greping all the kernel for this bit shows
> that the port status requests a warm-reset this way.
>
> This just happens, if its the only device on the root hub, the hub
> therefore resumes and the HCDs status_urb isn't yet available.
> If a warm-reset request is detected, this sets the hubs event_bits,
> which will prevent any auto-suspend and allows the hubs workqueue
> to warm-reset the port later in port_event.
>
> Signed-off-by: Jan-Marek Glogowski <glogow@xxxxxxxxxx>
> ---
>
> The original thread is "USB-C storage device not detected on USB 3.1 Gen 2
> host when plugged in after boot". A different patch, suggested by Mathias
> Nyman, didn't work for me. This patch was just rebased on usb-next, but not
> re-tested. Original tests are based on 5.0-rc.
>
> v1: This always warm-resets the ports in hub_activate, independent of the
> "enum hub_activation_type". Just had a single device to test.
>
> v2: I had the idea about the working device, if there is already a device
> connected to the hub and that a resume only on "type == HUB_RESUME" should
> be sufficient. This still works for me, but I didn't follow all the
> hub_activate callers everywhere and I'm definitly still missing a lot of
> knowledge about USB stuff. There is also HUB_RESET_RESUME with a slightly
> different code path. I don't know how to trigger this.
>
> v3: code unchanged to v2.
>
> v4: instead of handling the warm-reset directly from hub_activate by calling
> hub_port_reset, this defers the reset by setting the hubs event_bits of the
> port.
>
> ---
> drivers/usb/core/hub.c | 7 +++++++
> 1 file changed, 7 insertions(+)
>
> diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
> index bb0830c..8d4631c 100644
> --- a/drivers/usb/core/hub.c
> +++ b/drivers/usb/core/hub.c
> @@ -108,6 +108,8 @@ EXPORT_SYMBOL_GPL(ehci_cf_port_reset_rwsem);
> static void hub_release(struct kref *kref);
> static int usb_reset_and_verify_device(struct usb_device *udev);
> static int hub_port_disable(struct usb_hub *hub, int port1, int set_state);
> +static bool hub_port_warm_reset_required(struct usb_hub *hub, int port1,
> + u16 portstatus);
>
> static inline char *portspeed(struct usb_hub *hub, int portstatus)
> {
> @@ -1137,6 +1139,11 @@ static void hub_activate(struct usb_hub *hub, enum hub_activation_type type)
> USB_PORT_FEAT_ENABLE);
> }
>
> + /* Make sure a warm-reset request is handled by port_event */
> + if (type == HUB_RESUME &&
> + hub_port_warm_reset_required(hub, port1, portstatus))
> + set_bit(port1, hub->event_bits);
> +
> /*
> * Add debounce if USB3 link is in polling/link training state.
> * Link will automatically transition to Enabled state after
Acked-by: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>
