On Wed, Jun 22, 2022 at 05:46:53PM +0200, Lino Sanfilippo wrote: > From: Lino Sanfilippo <l.sanfilippo@xxxxxxxxxx> > > In serial8250_em485_config() the termination GPIO is set with the uart_port > spinlock held. This is an issue if setting the GPIO line can sleep (e.g. > since the concerning GPIO expander is connected via SPI or I2C). > > Fix this by setting the termination line outside of the uart_port spinlock > in the serial core. [...] > --- a/drivers/tty/serial/serial_core.c > +++ b/drivers/tty/serial/serial_core.c > @@ -1400,6 +1411,7 @@ static int uart_set_rs485_config(struct uart_port *port, > if (ret) > return ret; > uart_sanitize_serial_rs485(port, &rs485); > + uart_set_rs485_termination(port, &rs485); > > spin_lock_irqsave(&port->lock, flags); > ret = port->rs485_config(port, &rs485); That's one way to solve the issue. Another would be to push acquisition of the port spinlock down into drivers. I think in most drivers we don't need to take the port spinlock at all or only for a few specific register accesses. So taking the lock here in the midlayer is likely unwarranted. However, changing that requires going through every single driver's ->rs485_config() callback and checking whether it needs the lock or not. That's painful, but unavoidable in the long run. This patch just kicks the can down the road... Thanks, Lukas
