Re: Cypress CDC ACM serial port not working correctly with autosuspend

[Warren Togami <wtogami@gmail.com>]

On 6/7/23 08:10, Oliver Neukum wrote:
>
>> * udev rule: ATTRS{idProduct}=="55d4", ATTRS{idVendor}=="1a86", 
>> SUBSYSTEM=="usb", TEST=="power/control" ATTR{power/control}="on"
>> * usbcore.quirks=1a86:55d4:b
> [..]
>>
>> During the pandemic supply chain constraints led to some switching to 
>> the CH9102F which is described here as *almost* a drop-in 
>> replacement. Unfortunately the pinout differences might have 
>> mattered. I am uncertain if the board design could have been better 
>> but that is now in the past. Too many were mass produced so I am 
>> hoping for a USB quirk to stabilize this going forward.
>>
>> I have confirmed USB_QUIRK_RESET_RESUME allows this device to 
>> function for the same reason it works for the Cypress. I am uncertain 
>> if a narrower new quirk "ignore the remote wakeup bit" would work 
>> here. How can I test that?
>
> Please test the attached patch by giving the new 'p' quirk
> as usbcore.quirks
>
>     Regards
>         Oliver


Thanks! Tested your patch against 6.4.0-rc5. Both 
usbcore.quirks=1a86:55d4:b and usbcore.quirks=1a86:55d4:p allow the 
device to be fully functional. It even works through suspend+resume of 
the host. Without the quirk the only other way for this device to 
function at all is to turn off autosuspend.

How should we proceed? "p" would be the narrower quirk.  Would this be 
appropriate for drivers/usb/core/quirks.c?

Warren Togami