linux-kernel - Re: [PATCH] usb: hub: Resume hubs to find newly connected device

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Message-ID: <YbEnf2NUr/BCV4Gb@rowland.harvard.edu>
Date:   Wed, 8 Dec 2021 16:45:35 -0500
From:   Alan Stern <stern@...land.harvard.edu>
To:     Kai-Heng Feng <kai.heng.feng@...onical.com>
Cc:     gregkh@...uxfoundation.org, mathias.nyman@...ux.intel.com,
        Thinh Nguyen <Thinh.Nguyen@...opsys.com>,
        Bixuan Cui <cuibixuan@...wei.com>,
        Andrew Lunn <andrew@...n.ch>,
        Chris Chiu <chris.chiu@...onical.com>,
        Rajat Jain <rajatja@...gle.com>, linux-usb@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] usb: hub: Resume hubs to find newly connected device

On Wed, Dec 08, 2021 at 03:08:33PM +0800, Kai-Heng Feng wrote:
> When a new USB device gets plugged to nested hubs, the affected hub,
> which connects to usb 2-1.4-port2, doesn't report there's any change,
> hence the nested hubs go back to runtime suspend like nothing happened:

That's a bug in the hub.  When there's a change in the connection status 
of one of its ports, it should report this change to the kernel.

> [  281.032951] usb usb2: usb wakeup-resume
> [  281.032959] usb usb2: usb auto-resume
> [  281.032974] hub 2-0:1.0: hub_resume
> [  281.033011] usb usb2-port1: status 0263 change 0000
> [  281.033077] hub 2-0:1.0: state 7 ports 4 chg 0000 evt 0000
> [  281.049797] usb 2-1: usb wakeup-resume
> [  281.069800] usb 2-1: Waited 0ms for CONNECT
> [  281.069810] usb 2-1: finish resume
> [  281.070026] hub 2-1:1.0: hub_resume
> [  281.070250] usb 2-1-port4: status 0203 change 0000
> [  281.070272] usb usb2-port1: resume, status 0
> [  281.070282] hub 2-1:1.0: state 7 ports 4 chg 0010 evt 0000
> [  281.089813] usb 2-1.4: usb wakeup-resume
> [  281.109792] usb 2-1.4: Waited 0ms for CONNECT
> [  281.109801] usb 2-1.4: finish resume
> [  281.109991] hub 2-1.4:1.0: hub_resume
> [  281.110147] usb 2-1.4-port2: status 0263 change 0000
> [  281.110234] usb 2-1-port4: resume, status 0
> [  281.110239] usb 2-1-port4: status 0203, change 0000, 10.0 Gb/s
> [  281.110266] hub 2-1.4:1.0: state 7 ports 4 chg 0000 evt 0000
> [  281.110426] hub 2-1.4:1.0: hub_suspend
> [  281.110565] usb 2-1.4: usb auto-suspend, wakeup 1
> [  281.130998] hub 2-1:1.0: hub_suspend
> [  281.137788] usb 2-1: usb auto-suspend, wakeup 1
> [  281.142935] hub 2-0:1.0: state 7 ports 4 chg 0000 evt 0000
> [  281.177828] usb 2-1: usb wakeup-resume
> [  281.197839] usb 2-1: Waited 0ms for CONNECT
> [  281.197850] usb 2-1: finish resume
> [  281.197984] hub 2-1:1.0: hub_resume
> [  281.198203] usb 2-1-port4: status 0203 change 0000
> [  281.198228] usb usb2-port1: resume, status 0
> [  281.198237] hub 2-1:1.0: state 7 ports 4 chg 0010 evt 0000
> [  281.217835] usb 2-1.4: usb wakeup-resume
> [  281.237834] usb 2-1.4: Waited 0ms for CONNECT
> [  281.237845] usb 2-1.4: finish resume
> [  281.237990] hub 2-1.4:1.0: hub_resume
> [  281.238067] usb 2-1.4-port2: status 0263 change 0000
> [  281.238148] usb 2-1-port4: resume, status 0
> [  281.238152] usb 2-1-port4: status 0203, change 0000, 10.0 Gb/s
> [  281.238166] hub 2-1.4:1.0: state 7 ports 4 chg 0000 evt 0000
> [  281.238385] hub 2-1.4:1.0: hub_suspend
> [  281.238523] usb 2-1.4: usb auto-suspend, wakeup 1
> [  281.258076] hub 2-1:1.0: hub_suspend
> [  281.265744] usb 2-1: usb auto-suspend, wakeup 1
> [  281.285976] hub 2-0:1.0: hub_suspend
> [  281.285988] usb usb2: bus auto-suspend, wakeup 1
> 
> So in addition to change event, wakes up the port if it's a hub to find
> newly connected device:
> [  232.069881] usb usb2: usb wakeup-resume
> [  232.069889] usb usb2: usb auto-resume
> [  232.069904] hub 2-0:1.0: hub_resume
> [  232.069941] usb usb2-port1: status 0263 change 0000
> [  232.069962] hub 2-1:1.0: state 8 ports 4 chg 0000 evt 0000
> [  232.070034] hub 2-0:1.0: state 7 ports 4 chg 0000 evt 0000
> [  232.112701] usb 2-1: Waited 0ms for CONNECT
> [  232.112711] usb 2-1: finish resume
> [  232.112900] hub 2-1:1.0: hub_resume
> [  232.113218] usb 2-1-port4: status 0203 change 0000
> [  232.113267] hub 2-1.4:1.0: state 8 ports 4 chg 0000 evt 0000
> [  232.152679] usb 2-1.4: Waited 0ms for CONNECT
> [  232.152691] usb 2-1.4: finish resume
> [  232.152829] hub 2-1.4:1.0: hub_resume
> [  232.153057] usb 2-1.4-port2: status 0263 change 0000
> [  232.153094] hub 2-1.4.2:1.0: state 8 ports 3 chg 0000 evt 0000
> [  232.153155] usb 2-1-port4: resume, status 0
> [  232.153160] usb 2-1-port4: status 0203, change 0000, 10.0 Gb/s
> [  232.153192] hub 2-1.4:1.0: state 7 ports 4 chg 0000 evt 0000
> [  232.153235] hub 2-1:1.0: state 7 ports 4 chg 0000 evt 0000
> [  232.153244] usb usb2-port1: resume, status 0
> [  232.153274] usb 2-1.4.2: usb auto-resume
> [  232.153444] hub 2-1.4:1.0: state 7 ports 4 chg 0000 evt 0000
> [  232.220690] usb 2-1.4.2: Waited 0ms for CONNECT
> [  232.220702] usb 2-1.4.2: finish resume
> [  232.220849] hub 2-1.4.2:1.0: hub_resume
> [  232.220870] hub 2-1.4:1.0: state 7 ports 4 chg 0000 evt 0000
> [  232.220949] usb 2-1.4.2-port2: status 0203 change 0001
> [  232.328747] usb 2-1.4.2-port2: status 0203, change 0000, 5.0 Gb/s
> [  232.408838] usb 2-1.4.2.2: new SuperSpeed USB device number 5 using xhci_hcd
> [  232.429734] usb 2-1.4.2.2: skipped 1 descriptor after endpoint
> [  232.429745] usb 2-1.4.2.2: skipped 1 descriptor after endpoint
> [  232.429827] usb 2-1.4.2.2: default language 0x0409
> [  232.430192] usb 2-1.4.2.2: udev 5, busnum 2, minor = 132
> [  232.430197] usb 2-1.4.2.2: New USB device found, idVendor=0781, idProduct=5581, bcdDevice= 1.00
> [  232.430202] usb 2-1.4.2.2: New USB device strings: Mfr=1, Product=2, SerialNumber=3
> [  232.430206] usb 2-1.4.2.2: Product: Ultra
> [  232.430209] usb 2-1.4.2.2: Manufacturer: SanDisk
> [  232.430212] usb 2-1.4.2.2: SerialNumber: 4C530001170905105491
> [  232.430488] usb 2-1.4.2.2: usb_probe_device
> [  232.430493] usb 2-1.4.2.2: configuration #1 chosen from 1 choice
> [  232.431196] usb 2-1.4.2.2: Disabling U1 link state for device below second-tier hub.
> [  232.431199] usb 2-1.4.2.2: Plug device into first-tier hub to decrease power consumption.
> [  232.431469] usb 2-1.4.2.2: adding 2-1.4.2.2:1.0 (config #1, interface 0)
> [  232.431610] hub 2-1.4.2:1.0: state 7 ports 3 chg 0000 evt 0004
> 
> Signed-off-by: Kai-Heng Feng <kai.heng.feng@...onical.com>

So because of this buggy hub, you now want to wake up _every_ hub in the 
system whenever any wakeup event occurs?  Is this really a good idea?  
Is there a better way to solve the problem, such as a special quirk 
flag?

Alan Stern

> ---
>  drivers/usb/core/hub.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
> index 00070a8a65079..0c9442a8eab05 100644
> --- a/drivers/usb/core/hub.c
> +++ b/drivers/usb/core/hub.c
> @@ -1227,6 +1227,10 @@ static void hub_activate(struct usb_hub *hub, enum hub_activation_type type)
>  						port_resumed))
>  				set_bit(port1, hub->change_bits);
>  
> +			if ((portstatus & USB_PORT_STAT_CONNECTION) &&
> +			    usb_hub_to_struct_hub(udev))
> +				usb_kick_hub_wq(udev);
> +
>  		} else if (udev->persist_enabled) {
>  #ifdef CONFIG_PM
>  			udev->reset_resume = 1;
> -- 
> 2.32.0
>