| Message ID | 20200312125524.7812-5-jandryuk@gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | usb-serial: xHCI and timeout fixes | expand |
Jason Andryuk, le jeu. 12 mars 2020 08:55:23 -0400, a ecrit: > Linux guests wait ~30 seconds when closing the emulated /dev/ttyUSB0. > During that time, the kernel driver is sending many control URBs > requesting GetModemStat (5). Real hardware returns a status with > FTDI_THRE (Transmitter Holding Register) and FTDI_TEMT (Transmitter > Empty) set. QEMU leaves them clear, and it seems Linux is waiting for > FTDI_TEMT to be set to indicate the tx queue is empty before closing. > > Set the bits when responding to a GetModemStat query and avoid the > shutdown delay. > > Signed-off-by: Jason Andryuk <jandryuk@gmail.com> Reviewed-by: Samuel Thibault <samuel.thibault@ens-lyon.org> > --- > Looking at a USB dump for a real FTDI USB adapter, I see these bits set > in all the bulk URBs where QEMU currently has them clear. > --- > hw/usb/dev-serial.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/hw/usb/dev-serial.c b/hw/usb/dev-serial.c > index ef33bcd127..5389235f17 100644 > --- a/hw/usb/dev-serial.c > +++ b/hw/usb/dev-serial.c > @@ -332,7 +332,7 @@ static void usb_serial_handle_control(USBDevice *dev, USBPacket *p, > break; > case DeviceInVendor | FTDI_GET_MDM_ST: > data[0] = usb_get_modem_lines(s) | 1; > - data[1] = 0; > + data[1] = FTDI_THRE | FTDI_TEMT; > p->actual_length = 2; > break; > case DeviceOutVendor | FTDI_SET_EVENT_CHR: > -- > 2.24.1 >
diff --git a/hw/usb/dev-serial.c b/hw/usb/dev-serial.c index ef33bcd127..5389235f17 100644 --- a/hw/usb/dev-serial.c +++ b/hw/usb/dev-serial.c @@ -332,7 +332,7 @@ static void usb_serial_handle_control(USBDevice *dev, USBPacket *p, break; case DeviceInVendor | FTDI_GET_MDM_ST: data[0] = usb_get_modem_lines(s) | 1; - data[1] = 0; + data[1] = FTDI_THRE | FTDI_TEMT; p->actual_length = 2; break; case DeviceOutVendor | FTDI_SET_EVENT_CHR:
Linux guests wait ~30 seconds when closing the emulated /dev/ttyUSB0. During that time, the kernel driver is sending many control URBs requesting GetModemStat (5). Real hardware returns a status with FTDI_THRE (Transmitter Holding Register) and FTDI_TEMT (Transmitter Empty) set. QEMU leaves them clear, and it seems Linux is waiting for FTDI_TEMT to be set to indicate the tx queue is empty before closing. Set the bits when responding to a GetModemStat query and avoid the shutdown delay. Signed-off-by: Jason Andryuk <jandryuk@gmail.com> --- Looking at a USB dump for a real FTDI USB adapter, I see these bits set in all the bulk URBs where QEMU currently has them clear. --- hw/usb/dev-serial.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)