| Message ID | 20180321025241.19785-5-jk@ozlabs.org |
|---|---|
| State | Not Applicable, archived |
| Headers | show |
| Series | serial: implement flow control for ASPEED VUART driver | expand |
On 03/20/2018 09:52 PM, Jeremy Kerr wrote: > The aspeed VUART runs at LPC bus frequency, rather than being restricted > to a typical UART baud rate. This means that the VUART can receive a lot > of data, which can overrun tty flip buffers, and/or cause a large amount > of interrupt traffic. > > This change implements the uart_port->throttle & unthrottle callbacks, > implemented by disabling the receiver line status & received data > available IRQs. Tested-by: Eddie James <eajames@linux.vnet.ibm.com> > > Signed-off-by: Jeremy Kerr <jk@ozlabs.org> > --- > drivers/tty/serial/8250/8250_aspeed_vuart.c | 27 +++++++++++++++++++++++++++ > 1 file changed, 27 insertions(+) > > diff --git a/drivers/tty/serial/8250/8250_aspeed_vuart.c b/drivers/tty/serial/8250/8250_aspeed_vuart.c > index 33a801353114..50c082b4a1ac 100644 > --- a/drivers/tty/serial/8250/8250_aspeed_vuart.c > +++ b/drivers/tty/serial/8250/8250_aspeed_vuart.c > @@ -183,6 +183,30 @@ static void aspeed_vuart_shutdown(struct uart_port *uart_port) > serial8250_do_shutdown(uart_port); > } > > +static void aspeed_vuart_set_throttle(struct uart_port *port, bool throttle) > +{ > + unsigned char irqs = UART_IER_RLSI | UART_IER_RDI; > + struct uart_8250_port *up = up_to_u8250p(port); > + unsigned long flags; > + > + spin_lock_irqsave(&port->lock, flags); > + up->ier &= ~irqs; > + if (!throttle) > + up->ier |= irqs; > + serial_out(up, UART_IER, up->ier); > + spin_unlock_irqrestore(&port->lock, flags); > +} > + > +static void aspeed_vuart_throttle(struct uart_port *port) > +{ > + aspeed_vuart_set_throttle(port, true); > +} > + > +static void aspeed_vuart_unthrottle(struct uart_port *port) > +{ > + aspeed_vuart_set_throttle(port, false); > +} > + > static int aspeed_vuart_probe(struct platform_device *pdev) > { > struct uart_8250_port port; > @@ -212,6 +236,9 @@ static int aspeed_vuart_probe(struct platform_device *pdev) > port.port.mapsize = resource_size(res); > port.port.startup = aspeed_vuart_startup; > port.port.shutdown = aspeed_vuart_shutdown; > + port.port.throttle = aspeed_vuart_throttle; > + port.port.unthrottle = aspeed_vuart_unthrottle; > + port.port.status = UPSTAT_SYNC_FIFO; > port.port.dev = &pdev->dev; > > rc = sysfs_create_group(&vuart->dev->kobj, &aspeed_vuart_attr_group);
diff --git a/drivers/tty/serial/8250/8250_aspeed_vuart.c b/drivers/tty/serial/8250/8250_aspeed_vuart.c index 33a801353114..50c082b4a1ac 100644 --- a/drivers/tty/serial/8250/8250_aspeed_vuart.c +++ b/drivers/tty/serial/8250/8250_aspeed_vuart.c @@ -183,6 +183,30 @@ static void aspeed_vuart_shutdown(struct uart_port *uart_port) serial8250_do_shutdown(uart_port); } +static void aspeed_vuart_set_throttle(struct uart_port *port, bool throttle) +{ + unsigned char irqs = UART_IER_RLSI | UART_IER_RDI; + struct uart_8250_port *up = up_to_u8250p(port); + unsigned long flags; + + spin_lock_irqsave(&port->lock, flags); + up->ier &= ~irqs; + if (!throttle) + up->ier |= irqs; + serial_out(up, UART_IER, up->ier); + spin_unlock_irqrestore(&port->lock, flags); +} + +static void aspeed_vuart_throttle(struct uart_port *port) +{ + aspeed_vuart_set_throttle(port, true); +} + +static void aspeed_vuart_unthrottle(struct uart_port *port) +{ + aspeed_vuart_set_throttle(port, false); +} + static int aspeed_vuart_probe(struct platform_device *pdev) { struct uart_8250_port port; @@ -212,6 +236,9 @@ static int aspeed_vuart_probe(struct platform_device *pdev) port.port.mapsize = resource_size(res); port.port.startup = aspeed_vuart_startup; port.port.shutdown = aspeed_vuart_shutdown; + port.port.throttle = aspeed_vuart_throttle; + port.port.unthrottle = aspeed_vuart_unthrottle; + port.port.status = UPSTAT_SYNC_FIFO; port.port.dev = &pdev->dev; rc = sysfs_create_group(&vuart->dev->kobj, &aspeed_vuart_attr_group);
The aspeed VUART runs at LPC bus frequency, rather than being restricted to a typical UART baud rate. This means that the VUART can receive a lot of data, which can overrun tty flip buffers, and/or cause a large amount of interrupt traffic. This change implements the uart_port->throttle & unthrottle callbacks, implemented by disabling the receiver line status & received data available IRQs. Signed-off-by: Jeremy Kerr <jk@ozlabs.org> --- drivers/tty/serial/8250/8250_aspeed_vuart.c | 27 +++++++++++++++++++++++++++ 1 file changed, 27 insertions(+)