linux-kernel - Re: [PATCH v2] USB: core: Disable LPM only for non-suspended ports

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Message-ID: <a9f767eb-2196-4273-ba1a-19b07ccdafd8@rowland.harvard.edu>
Date: Thu, 5 Dec 2024 10:06:11 -0500
From: Alan Stern <stern@...land.harvard.edu>
To: Kai-Heng Feng <kaihengf@...dia.com>
Cc: gregkh@...uxfoundation.org, mathias.nyman@...ux.intel.com,
	linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
	Wayne Chang <waynec@...dia.com>, stable@...r.kernel.org
Subject: Re: [PATCH v2] USB: core: Disable LPM only for non-suspended ports

On Thu, Dec 05, 2024 at 05:12:15PM +0800, Kai-Heng Feng wrote:
> There's USB error when tegra board is shutting down:
> [  180.919315] usb 2-3: Failed to set U1 timeout to 0x0,error code -113
> [  180.919995] usb 2-3: Failed to set U1 timeout to 0xa,error code -113
> [  180.920512] usb 2-3: Failed to set U2 timeout to 0x4,error code -113
> [  186.157172] tegra-xusb 3610000.usb: xHCI host controller not responding, assume dead
> [  186.157858] tegra-xusb 3610000.usb: HC died; cleaning up
> [  186.317280] tegra-xusb 3610000.usb: Timeout while waiting for evaluate context command
> 
> The issue is caused by disabling LPM on already suspended ports.
> 
> For USB2 LPM, the LPM is already disabled during port suspend. For USB3
> LPM, port won't transit to U1/U2 when it's already suspended in U3,
> hence disabling LPM is only needed for ports that are not suspended.
> 
> Cc: Wayne Chang <waynec@...dia.com>
> Cc: stable@...r.kernel.org
> Fixes: d920a2ed8620 ("usb: Disable USB3 LPM at shutdown")
> Signed-off-by: Kai-Heng Feng <kaihengf@...dia.com>
> ---
> v2:
>  Add "Cc: stable@...r.kernel.org"
> 
>  drivers/usb/core/port.c | 7 ++++---
>  1 file changed, 4 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/usb/core/port.c b/drivers/usb/core/port.c
> index e7da2fca11a4..d50b9e004e76 100644
> --- a/drivers/usb/core/port.c
> +++ b/drivers/usb/core/port.c
> @@ -452,10 +452,11 @@ static int usb_port_runtime_suspend(struct device *dev)
>  static void usb_port_shutdown(struct device *dev)
>  {
>  	struct usb_port *port_dev = to_usb_port(dev);
> +	struct usb_device *udev = port_dev->child;
>  
> -	if (port_dev->child) {
> -		usb_disable_usb2_hardware_lpm(port_dev->child);
> -		usb_unlocked_disable_lpm(port_dev->child);
> +	if (udev && !pm_runtime_suspended(&udev->dev)) {

Instead of testing !pm_runtime_suspended(&udev->dev), it would be better 
to test udev->port_is_suspended.  This field records the actual status 
of the device's upstream port, whereas in some circumstances 
pm_runtime_suspended() will return true when the port is in U0.

Alan Stern

> +		usb_disable_usb2_hardware_lpm(udev);
> +		usb_unlocked_disable_lpm(udev);
>  	}
>  }
>  
> -- 
> 2.47.0