Patch "serial: amba-pl011: Fix DMA transmission in RS485 mode" has been added to the 6.6-stable tree

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This is a note to let you know that I've just added the patch titled

    serial: amba-pl011: Fix DMA transmission in RS485 mode

to the 6.6-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     serial-amba-pl011-fix-dma-transmission-in-rs485-mode.patch
and it can be found in the queue-6.6 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.


>From 3b69e32e151bc4a4e3c785cbdb1f918d5ee337ed Mon Sep 17 00:00:00 2001
From: Lino Sanfilippo <l.sanfilippo@xxxxxxxxxx>
Date: Fri, 16 Feb 2024 23:47:08 +0100
Subject: serial: amba-pl011: Fix DMA transmission in RS485 mode

From: Lino Sanfilippo <l.sanfilippo@xxxxxxxxxx>

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@xxxxxxxxxxxxxxx
Fixes: 8d479237727c ("serial: amba-pl011: add RS485 support")
Signed-off-by: Lino Sanfilippo <l.sanfilippo@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20240216224709.9928-2-l.sanfilippo@xxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 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
@@ -1345,11 +1345,41 @@ 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);
 }
@@ -1431,42 +1461,12 @@ 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;


Patches currently in stable-queue which might be from l.sanfilippo@xxxxxxxxxx are

queue-6.6/serial-amba-pl011-fix-dma-transmission-in-rs485-mode.patch
queue-6.6/serial-stm32-do-not-always-set-ser_rs485_rx_during_tx-if-rs485-is-enabled.patch




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