[PATCH 5.15 095/245] serial: amba-pl011: Fix DMA transmission in RS485 mode

Greg Kroah-Hartman
2024-02-27T14:06:35Z

From: Lino Sanfilippo <l.sanfilippo@kunbus.com>

commit 3b69e32e151bc4a4e3c785cbdb1f918d5ee337ed upstream.

When DMA is used in RS485 mode make sure that the UARTs tx section is
enabled before the DMA buffers are queued for transmission.

Cc: stable@vger.kernel.org
Fixes: 8d479237727c ("serial: amba-pl011: add RS485 support")
Signed-off-by: Lino Sanfilippo <l.sanfilippo@kunbus.com>
Link: https://lore.kernel.org/r/20240216224709.9928-2-l.sanfilippo@kunbus.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/tty/serial/amba-pl011.c | 60 ++++++++++++++++++++--------------------
1 file changed, 30 insertions(+), 30 deletions(-)

--- a/drivers/tty/serial/amba-pl011.c
+++ b/drivers/tty/serial/amba-pl011.c
@@ -1350,11 +1350,41 @@ static void pl011_start_tx_pio(struct ua
}
}

+static void pl011_rs485_tx_start(struct uart_amba_port *uap)
+{
+ struct uart_port *port = &uap->port;
+ u32 cr;
+
+ /* Enable transmitter */
+ cr = pl011_read(uap, REG_CR);
+ cr |= UART011_CR_TXE;
+
+ /* Disable receiver if half-duplex */
+ if (!(port->rs485.flags & SER_RS485_RX_DURING_TX))
+ cr &= ~UART011_CR_RXE;
+
+ if (port->rs485.flags & SER_RS485_RTS_ON_SEND)
+ cr &= ~UART011_CR_RTS;
+ else
+ cr |= UART011_CR_RTS;
+
+ pl011_write(cr, uap, REG_CR);
+
+ if (port->rs485.delay_rts_before_send)
+ mdelay(port->rs485.delay_rts_before_send);
+
+ uap->rs485_tx_started = true;
+}
+
static void pl011_start_tx(struct uart_port *port)
{
struct uart_amba_port *uap =
container_of(port, struct uart_amba_port, port);

+ if ((uap->port.rs485.flags & SER_RS485_ENABLED) &&
+ !uap->rs485_tx_started)
+ pl011_rs485_tx_start(uap);
+
if (!pl011_dma_tx_start(uap))
pl011_start_tx_pio(uap);
}
@@ -1436,42 +1466,12 @@ static bool pl011_tx_char(struct uart_am
return true;
}

-static void pl011_rs485_tx_start(struct uart_amba_port *uap)
-{
- struct uart_port *port = &uap->port;
- u32 cr;
-
- /* Enable transmitter */
- cr = pl011_read(uap, REG_CR);
- cr |= UART011_CR_TXE;
-
- /* Disable receiver if half-duplex */
- if (!(port->rs485.flags & SER_RS485_RX_DURING_TX))
- cr &= ~UART011_CR_RXE;
-
- if (port->rs485.flags & SER_RS485_RTS_ON_SEND)
- cr &= ~UART011_CR_RTS;
- else
- cr |= UART011_CR_RTS;
-
- pl011_write(cr, uap, REG_CR);
-
- if (port->rs485.delay_rts_before_send)
- mdelay(port->rs485.delay_rts_before_send);
-
- uap->rs485_tx_started = true;
-}
-
/* Returns true if tx interrupts have to be (kept) enabled */
static bool pl011_tx_chars(struct uart_amba_port *uap, bool from_irq)
{
struct circ_buf *xmit = &uap->port.state->xmit;
int count = uap->fifosize >> 1;

- if ((uap->port.rs485.flags & SER_RS485_ENABLED) &&
- !uap->rs485_tx_started)
- pl011_rs485_tx_start(uap);
-
if (uap->port.x_char) {
if (!pl011_tx_char(uap, uap->port.x_char, from_irq))
return true;