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

[Kai-Heng Feng <kaihengf@nvidia.com>]

On 2024/12/5 11:06 PM, Alan Stern wrote:
> External email: Use caution opening links or attachments
> 
> 
> 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@nvidia.com>
>> Cc: stable@vger.kernel.org
>> Fixes: d920a2ed8620 ("usb: Disable USB3 LPM at shutdown")
>> Signed-off-by: Kai-Heng Feng <kaihengf@nvidia.com>
>> ---
>> v2:
>>   Add "Cc: stable@vger.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.

Thanks for the tip. This indeed is a better approach. Will send another revision.

Kai-Heng


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