Currently to be the same as resume(). This will just avoid re-enumeration of the modem device on every system resume. This exists only because the usb core will re-enumerate *any* device whos' driver doesn't have reset_resume() implemented. A call trace: Jun 23 11:15:43 pureos kernel: usb_serial_disconnect+0x58/0x180 [usbserial] Jun 23 11:15:43 pureos kernel: usb_unbind_interface+0x84/0x290 [usbcore] Jun 23 11:15:43 pureos kernel: device_remove+0x78/0x90 Jun 23 11:15:43 pureos kernel: device_release_driver_internal+0x1e4/0x250 Jun 23 11:15:43 pureos kernel: device_release_driver+0x24/0x30 Jun 23 11:15:43 pureos kernel: usb_forced_unbind_intf+0xac/0xd4 [usbcore] Jun 23 11:15:43 pureos kernel: unbind_marked_interfaces.isra.0+0x5c/0x80 [usbcore] Jun 23 11:15:43 pureos kernel: usb_resume+0x78/0x8c [usbcore] Jun 23 11:15:43 pureos kernel: usb_dev_resume+0x20/0x30 [usbcore] Jun 23 11:15:43 pureos kernel: dpm_run_callback+0x60/0x1f0 Jun 23 11:15:43 pureos kernel: device_resume+0x9c/0x1f4 where usb_resume_inteface() sets needs_binding here https://elixir.bootlin.com/linux/latest/source/drivers/usb/core/driver.c#L1353 because of no reset_resume() implementation. This hack is even suggested in some modems' application notes as can be found in discussion here https://invent.kde.org/teams/plasma-mobile/issues/-/issues/3#note_218386 Signed-off-by: Martin Kepplinger <martin.kepplinger@xxxxxxx> --- drivers/usb/serial/option.c | 14 ++++++++++++++ 1 file changed, 14 insertions(+) diff --git a/drivers/usb/serial/option.c b/drivers/usb/serial/option.c index dee79c7d82d5..58526bf8684d 100644 --- a/drivers/usb/serial/option.c +++ b/drivers/usb/serial/option.c @@ -46,6 +46,7 @@ static int option_probe(struct usb_serial *serial, static int option_attach(struct usb_serial *serial); static void option_release(struct usb_serial *serial); static void option_instat_callback(struct urb *urb); +static int option_reset_resume(struct usb_serial *serial); /* Vendor and product IDs */ #define OPTION_VENDOR_ID 0x0AF0 @@ -2227,6 +2228,7 @@ static struct usb_serial_driver option_1port_device = { #ifdef CONFIG_PM .suspend = usb_wwan_suspend, .resume = usb_wwan_resume, + .reset_resume = option_reset_resume, #endif }; @@ -2373,6 +2375,18 @@ static void option_instat_callback(struct urb *urb) } } +static int option_reset_resume(struct usb_serial *serial) +{ + /* + * We simply call resume() because this implementation only + * exists because the USB core will un- and rebind any driver + * during system resume that does *not* have a reset_resume() + * implementation; see usb_resume_interface() in core/driver.c + * We want to avoid that unconditional removal/addition. + */ + return usb_wwan_resume(serial); +} + MODULE_AUTHOR(DRIVER_AUTHOR); MODULE_DESCRIPTION(DRIVER_DESC); MODULE_LICENSE("GPL v2"); -- 2.30.2
