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From a3749ee48539fa832b1832cdcae26d34e5d20f00 Mon Sep 17 00:00:00 2001
From: Phil Elwell <phil@raspberrypi.org>
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 <phil@raspberrypi.org>
---
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 =
@@ -2164,6 +2190,8 @@ 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,
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