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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: Jeremy Kerr <jk@ozlabs.org>
Tested-by: Eddie James <eajames@linux.vnet.ibm.com>
Tested-by: Joel Stanley <joel@jms.id.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Jeremy Kerr 2018-03-27 11:48:26 +08:00 committed by Greg Kroah-Hartman
parent ebbaf9ab9e
commit 989983ea84
1 changed files with 27 additions and 0 deletions
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27
drivers/tty/serial/8250/8250_aspeed_vuart.c
View File

@ -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);