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Subject: Re: [PATCH v2 2/2] USB: core: Attempt power cycle port when it's in
 eSS.Disabled state
From:   Kai-Heng Feng <kai.heng.feng@canonical.com>
In-Reply-To: <20191129174115.31683-2-kai.heng.feng@canonical.com>
Date:   Wed, 11 Dec 2019 21:45:26 +0800
Cc:     stern@rowland.harvard.edu, linux-usb@vger.kernel.org,
        linux-kernel@vger.kernel.org
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Message-Id: <62C4527A-5231-4A69-BE7C-9844E2123A90@canonical.com>
References: <20191129174115.31683-1-kai.heng.feng@canonical.com>
 <20191129174115.31683-2-kai.heng.feng@canonical.com>
To:     Greg KH <gregkh@linuxfoundation.org>
Sender: linux-kernel-owner@vger.kernel.org
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> On Nov 30, 2019, at 01:41, Kai-Heng Feng <kai.heng.feng@canonical.com> wrote:
> 
> On Dell TB16, Realtek USB ethernet (r8152) connects to an SMSC hub which
> then connects to ASMedia xHCI's root hub:
> 
> /:  Bus 04.Port 1: Dev 1, Class=root_hub, Driver=xhci_hcd/2p, 5000M
>    |__ Port 1: Dev 2, If 0, Class=Hub, Driver=hub/7p, 5000M
>            |__ Port 2: Dev 3, If 0, Class=Vendor Specific Class, Driver=r8152, 5000M
> 
> Bus 004 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
> Bus 004 Device 002: ID 0424:5537 Standard Microsystems Corp. USB5537B
> Bus 004 Device 003: ID 0bda:8153 Realtek Semiconductor Corp. RTL8153 Gigabit Ethernet Adapter
> 
> The SMSC hub may disconnect after system resume from suspend. When this
> happens, the reset resume attempt fails, and the last resort to disable
> the port and see something comes up later, also fails.
> 
> When the issue occurs, the link state stays in eSS.Disabled state
> despite the warm reset attempts. Accoding to spec this can be caused by
> invalid VBus, after some expiremets, the SMSC hub can be brought back
> after a powercycle.
> 
> So let's power cycle the port at the end of reset resume attempt, if
> it's in eSS.Disabled state.

If there's no objection, can this fix be reviewed and merged?

Kai-Heng

> 
> Signed-off-by: Kai-Heng Feng <kai.heng.feng@canonical.com>
> ---
> v2:
> - Lower dev_info() to dev_dbg().
> 
> drivers/usb/core/hub.c | 16 ++++++++++++++++
> 1 file changed, 16 insertions(+)
> 
> diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
> index 6b6cd76ac5e6..a2e6001046f5 100644
> --- a/drivers/usb/core/hub.c
> +++ b/drivers/usb/core/hub.c
> @@ -2739,6 +2739,18 @@ static bool hub_port_warm_reset_required(struct usb_hub *hub, int port1,
> 		|| link_state == USB_SS_PORT_LS_COMP_MOD;
> }
> 
> +static bool hub_port_power_cycle_required(struct usb_hub *hub, int port1,
> +		u16 portstatus)
> +{
> +	u16 link_state;
> +
> +	if (!hub_is_superspeed(hub->hdev))
> +		return false;
> +
> +	link_state = portstatus & USB_PORT_STAT_LINK_STATE;
> +	return link_state == USB_SS_PORT_LS_SS_DISABLED;
> +}
> +
> static void hub_port_power_cycle(struct usb_hub *hub, int port1)
> {
> 	struct usb_port *port_dev = hub->ports[port1  - 1];
> @@ -3601,6 +3613,10 @@ int usb_port_resume(struct usb_device *udev, pm_message_t msg)
> 	if (status < 0) {
> 		dev_dbg(&udev->dev, "can't resume, status %d\n", status);
> 		hub_port_logical_disconnect(hub, port1);
> +		if (hub_port_power_cycle_required(hub, port1, portstatus)) {
> +			dev_dbg(&udev->dev, "device in disabled state, attempt power cycle\n");
> +			hub_port_power_cycle(hub, port1);
> +		}
> 	} else  {
> 		/* Try to enable USB2 hardware LPM */
> 		usb_enable_usb2_hardware_lpm(udev);
> -- 
> 2.17.1
>