From d4f4b57c667141ca98711cfcb30ae2b8deb1a034 Mon Sep 17 00:00:00 2001 From: Phil Elwell Date: Fri, 24 Jan 2020 11:38:28 +0000 Subject: [PATCH] tty: amba-pl011: Add un/throttle support The PL011 driver lacks throttle and unthrottle methods. As a result, sending more data to the Pi than it can immediately sink while CRTSCTS is enabled causes a NULL pointer to be followed. Add a throttle handler that disables the RX interrupts, and an unthrottle handler that reenables them. Signed-off-by: Phil Elwell --- drivers/tty/serial/amba-pl011.c | 28 ++++++++++++++++++++++++++++ 1 file changed, 28 insertions(+) --- a/drivers/tty/serial/amba-pl011.c +++ b/drivers/tty/serial/amba-pl011.c @@ -1323,6 +1323,32 @@ static void pl011_start_tx(struct uart_p pl011_start_tx_pio(uap); } +static void pl011_throttle(struct uart_port *port) +{ + struct uart_amba_port *uap = + container_of(port, struct uart_amba_port, port); + unsigned long flags; + + spin_lock_irqsave(&uap->port.lock, flags); + uap->im &= ~(UART011_RTIM | UART011_RXIM); + pl011_write(uap->im, uap, REG_IMSC); + spin_unlock_irqrestore(&uap->port.lock, flags); +} + +static void pl011_unthrottle(struct uart_port *port) +{ + struct uart_amba_port *uap = + container_of(port, struct uart_amba_port, port); + unsigned long flags; + + spin_lock_irqsave(&uap->port.lock, flags); + uap->im |= UART011_RTIM; + if (!pl011_dma_rx_running(uap)) + uap->im |= UART011_RXIM; + pl011_write(uap->im, uap, REG_IMSC); + spin_unlock_irqrestore(&uap->port.lock, flags); +} + static void pl011_stop_rx(struct uart_port *port) { struct uart_amba_port *uap = @@ -2165,6 +2191,8 @@ static const struct uart_ops amba_pl011_ .stop_tx = pl011_stop_tx, .start_tx = pl011_start_tx, .stop_rx = pl011_stop_rx, + .throttle = pl011_throttle, + .unthrottle = pl011_unthrottle, .enable_ms = pl011_enable_ms, .break_ctl = pl011_break_ctl, .startup = pl011_startup,