Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit 989983ea authored by Jeremy Kerr's avatar Jeremy Kerr Committed by Greg Kroah-Hartman
Browse files

serial/aspeed-vuart: Implement rx throttling 



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: default avatarJeremy Kerr <jk@ozlabs.org>
Tested-by: default avatarEddie James <eajames@linux.vnet.ibm.com>
Tested-by: default avatarJoel Stanley <joel@jms.id.au>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent ebbaf9ab

drivers/tty/serial/8250/8250_aspeed_vuart.c

+27 −0
Original line number Diff line number Diff line
@@ -179,6 +179,30 @@ 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;
@@ -208,6 +232,9 @@ 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);