target/linux/brcm2708/patches-4.19/950-0796-tty-amba-pl011-Add-un-throttle-support.patch

   1 From d4f4b57c667141ca98711cfcb30ae2b8deb1a034 Mon Sep 17 00:00:00 2001
   2 From: Phil Elwell <phil@raspberrypi.org>
   3 Date: Fri, 24 Jan 2020 11:38:28 +0000
   4 Subject: [PATCH] tty: amba-pl011: Add un/throttle support
   5
   6 The PL011 driver lacks throttle and unthrottle methods. As a result,
   7 sending more data to the Pi than it can immediately sink while CRTSCTS
   8 is enabled causes a NULL pointer to be followed.
   9
  10 Add a throttle handler that disables the RX interrupts, and an
  11 unthrottle handler that reenables them.
  12
  13 Signed-off-by: Phil Elwell <phil@raspberrypi.org>
  14 ---
  15  drivers/tty/serial/amba-pl011.c | 28 ++++++++++++++++++++++++++++
  16  1 file changed, 28 insertions(+)
  17
  18 --- a/drivers/tty/serial/amba-pl011.c
  19 +++ b/drivers/tty/serial/amba-pl011.c
  20 @@ -1323,6 +1323,32 @@ static void pl011_start_tx(struct uart_p
  21                 pl011_start_tx_pio(uap);
  22  }
  23
  24 +static void pl011_throttle(struct uart_port *port)
  25 +{
  26 +       struct uart_amba_port *uap =
  27 +           container_of(port, struct uart_amba_port, port);
  28 +       unsigned long flags;
  29 +
  30 +       spin_lock_irqsave(&uap->port.lock, flags);
  31 +       uap->im &= ~(UART011_RTIM | UART011_RXIM);
  32 +       pl011_write(uap->im, uap, REG_IMSC);
  33 +       spin_unlock_irqrestore(&uap->port.lock, flags);
  34 +}
  35 +
  36 +static void pl011_unthrottle(struct uart_port *port)
  37 +{
  38 +       struct uart_amba_port *uap =
  39 +           container_of(port, struct uart_amba_port, port);
  40 +       unsigned long flags;
  41 +
  42 +       spin_lock_irqsave(&uap->port.lock, flags);
  43 +       uap->im |= UART011_RTIM;
  44 +       if (!pl011_dma_rx_running(uap))
  45 +           uap->im |= UART011_RXIM;
  46 +       pl011_write(uap->im, uap, REG_IMSC);
  47 +       spin_unlock_irqrestore(&uap->port.lock, flags);
  48 +}
  49 +
  50  static void pl011_stop_rx(struct uart_port *port)
  51  {
  52         struct uart_amba_port *uap =
  53 @@ -2165,6 +2191,8 @@ static const struct uart_ops amba_pl011_
  54         .stop_tx        = pl011_stop_tx,
  55         .start_tx       = pl011_start_tx,
  56         .stop_rx        = pl011_stop_rx,
  57 +       .throttle       = pl011_throttle,
  58 +       .unthrottle     = pl011_unthrottle,
  59         .enable_ms      = pl011_enable_ms,
  60         .break_ctl      = pl011_break_ctl,
  61         .startup        = pl011_startup,