Hi Alan,
On Thu, Jul 11, 2013 at 02:58:04PM -0400, Alan Stern wrote:
> The hub driver was recently changed to use "global" suspend for system
> suspend transitions on non-SuperSpeed buses. This means that we don't
> suspend devices individually by setting the suspend feature on the
> upstream hub port; instead devices all go into suspend automatically
> when the root hub stops transmitting packets. The idea was to save
> time and to avoid certain kinds of wakeup races.
>
> Now it turns out that many hubs are buggy; they don't relay wakeup
> requests from a downstream port to their upstream port if the
> downstream port's suspend feature is not set (depending on the speed
> of the downstream port, whether or not the hub is enabled for remote
> wakeup, and possibly other factors).
>
Could you explain that how can you make sure the root cause is unable
to relay wakup requests from downstream port to upstream port if
downstream port's suspend feature is not set? The OS is unable wakeup
from S3 at that time. We can't fetch dmesg log and serial port is
suspend either at that time. Did you use any other tools to trace this
issue? Could you teach me? Actually, I was encoutered this issue
either.
Thanks,
Rui
> We can't have hubs dropping wakeup requests. Therefore this patch
> goes partway back to the old policy: It sets the suspend feature for a
> port if the device attached to that port or any of its descendants is
> enabled for wakeup. People will still be able to benefit from the
> time savings if they don't care about wakeup and leave it disabled on
> all their devices.
>
> In order to accomplish this, the patch adds a new field to the usb_hub
> structure: wakeup_enabled_descendants is a count of how many devices
> below a suspended hub are enabled for remote wakeup. A corresponding
> new subroutine determines the number of wakeup-enabled devices at or
> below an arbitrary suspended USB device.
>
> This should be applied to the 3.10 stable kernel.
>
> Signed-off-by: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>
> Reported-and-tested-by: Toralf Förster <toralf.foerster@xxxxxx>
> CC: <stable@xxxxxxxxxxxxxxx>
>
> ---
>
>
> [as1692]
>
> drivers/usb/core/hub.c | 39 +++++++++++++++++++++++++++++++--------
> drivers/usb/core/hub.h | 3 +++
> 2 files changed, 34 insertions(+), 8 deletions(-)
>
> Index: usb-3.10/drivers/usb/core/hub.h
> ===================================================================
> --- usb-3.10.orig/drivers/usb/core/hub.h
> +++ usb-3.10/drivers/usb/core/hub.h
> @@ -59,6 +59,9 @@ struct usb_hub {
> struct usb_tt tt; /* Transaction Translator */
>
> unsigned mA_per_port; /* current for each child */
> +#ifdef CONFIG_PM
> + unsigned wakeup_enabled_descendants;
> +#endif
>
> unsigned limited_power:1;
> unsigned quiescing:1;
> Index: usb-3.10/drivers/usb/core/hub.c
> ===================================================================
> --- usb-3.10.orig/drivers/usb/core/hub.c
> +++ usb-3.10/drivers/usb/core/hub.c
> @@ -2848,6 +2848,15 @@ static int usb_disable_function_remotewa
> USB_CTRL_SET_TIMEOUT);
> }
>
> +/* Count of wakeup-enabled devices at or below udev */
> +static unsigned wakeup_enabled_descendants(struct usb_device *udev)
> +{
> + struct usb_hub *hub = usb_hub_to_struct_hub(udev);
> +
> + return udev->do_remote_wakeup +
> + (hub ? hub->wakeup_enabled_descendants : 0);
> +}
> +
> /*
> * usb_port_suspend - suspend a usb device's upstream port
> * @udev: device that's no longer in active use, not a root hub
> @@ -2888,8 +2897,8 @@ static int usb_disable_function_remotewa
> * Linux (2.6) currently has NO mechanisms to initiate that: no khubd
> * timer, no SRP, no requests through sysfs.
> *
> - * If Runtime PM isn't enabled or used, non-SuperSpeed devices really get
> - * suspended only when their bus goes into global suspend (i.e., the root
> + * If Runtime PM isn't enabled or used, non-SuperSpeed devices may not get
> + * suspended until their bus goes into global suspend (i.e., the root
> * hub is suspended). Nevertheless, we change @udev->state to
> * USB_STATE_SUSPENDED as this is the device's "logical" state. The actual
> * upstream port setting is stored in @udev->port_is_suspended.
> @@ -2960,15 +2969,21 @@ int usb_port_suspend(struct usb_device *
> /* see 7.1.7.6 */
> if (hub_is_superspeed(hub->hdev))
> status = hub_set_port_link_state(hub, port1, USB_SS_PORT_LS_U3);
> - else if (PMSG_IS_AUTO(msg))
> - status = set_port_feature(hub->hdev, port1,
> - USB_PORT_FEAT_SUSPEND);
> +
> /*
> * For system suspend, we do not need to enable the suspend feature
> * on individual USB-2 ports. The devices will automatically go
> * into suspend a few ms after the root hub stops sending packets.
> * The USB 2.0 spec calls this "global suspend".
> + *
> + * However, many USB hubs have a bug: They don't relay wakeup requests
> + * from a downstream port if the port's suspend feature isn't on.
> + * Therefore we will turn on the suspend feature if udev or any of its
> + * descendants is enabled for remote wakeup.
> */
> + else if (PMSG_IS_AUTO(msg) || wakeup_enabled_descendants(udev) > 0)
> + status = set_port_feature(hub->hdev, port1,
> + USB_PORT_FEAT_SUSPEND);
> else {
> really_suspend = false;
> status = 0;
> @@ -3003,15 +3018,16 @@ int usb_port_suspend(struct usb_device *
> if (!PMSG_IS_AUTO(msg))
> status = 0;
> } else {
> - /* device has up to 10 msec to fully suspend */
> dev_dbg(&udev->dev, "usb %ssuspend, wakeup %d\n",
> (PMSG_IS_AUTO(msg) ? "auto-" : ""),
> udev->do_remote_wakeup);
> - usb_set_device_state(udev, USB_STATE_SUSPENDED);
> if (really_suspend) {
> udev->port_is_suspended = 1;
> +
> + /* device has up to 10 msec to fully suspend */
> msleep(10);
> }
> + usb_set_device_state(udev, USB_STATE_SUSPENDED);
> }
>
> /*
> @@ -3293,7 +3309,11 @@ static int hub_suspend(struct usb_interf
> unsigned port1;
> int status;
>
> - /* Warn if children aren't already suspended */
> + /*
> + * Warn if children aren't already suspended.
> + * Also, add up the number of wakeup-enabled descendants.
> + */
> + hub->wakeup_enabled_descendants = 0;
> for (port1 = 1; port1 <= hdev->maxchild; port1++) {
> struct usb_device *udev;
>
> @@ -3303,6 +3323,9 @@ static int hub_suspend(struct usb_interf
> if (PMSG_IS_AUTO(msg))
> return -EBUSY;
> }
> + if (udev)
> + hub->wakeup_enabled_descendants +=
> + wakeup_enabled_descendants(udev);
> }
>
> if (hdev->do_remote_wakeup && hub->quirk_check_port_auto_suspend) {
>
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