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@xxxxxxxxxx>
Tested-by: Eddie James <eajames@xxxxxxxxxxxxxxxxxx>
---
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 74a408d9db24..cd1bb49dadfe 100644
--- a/drivers/tty/serial/8250/8250_aspeed_vuart.c
+++ b/drivers/tty/serial/8250/8250_aspeed_vuart.c
@@ -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);
--
2.14.1
--
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