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patch "serial: pch: don't overwrite xmit->buf[0] by x_char" added to tty-next

PATCH [email protected] 1 participant 1 message May 9, 2022

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Stable branch TTY layer and serial drivers
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This is a note to let you know that I've just added the patch titled

    serial: pch: don't overwrite xmit->buf[0] by x_char

to my tty git tree which can be found at
git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty.git
in the tty-next branch.

The patch will show up in the next release of the linux-next tree (usually sometime within the next 24 hours during the week.)

The patch will also be merged in the next major kernel release during the merge window.

If you have any questions about this process, please let me know.

From d9f3af4fbb1d955bbaf872d9e76502f6e3e803cb Mon Sep 17 00:00:00 2001
From: Jiri Slaby <[email protected]>
Date: Tue, 3 May 2022 10:08:03 +0200
Subject: serial: pch: don't overwrite xmit->buf[0] by x_char

When x_char is to be sent, the TX path overwrites whatever is in the circular buffer at offset 0 with x_char and sends it using pch_uart_hal_write(). I don't understand how this was supposed to work if xmit->buf[0] already contained some character. It must have been lost.

Remove this whole pop_tx_x() concept and do the work directly in the callers. (Without printing anything using dev_dbg().)

Cc <[email protected]>
Fixes 3c6a483275f4 (Serial: EG20T: add PCH_UART driver)
Signed-off-by Jiri Slaby <[email protected]>
Link https://lore.kernel.org/r/[email protected] open here
Signed-off-by Greg Kroah-Hartman <[email protected]>
---
 drivers/tty/serial/pch_uart.c | 27 +++++++--------------------
 1 file changed, 7 insertions(+), 20 deletions(-)
drivers/tty/serial/pch_uart.c +7 -20
index f872613a5e83..6cb631487383 100644
@@ -624,22 +624,6 @@ static int push_rx(struct eg20t_port *priv, const unsigned char *buf,
 	return 0;
 }
 
-static int pop_tx_x(struct eg20t_port *priv, unsigned char *buf)
-{
-	int ret = 0;
-	struct uart_port *port = &priv->port;
-
-	if (port->x_char) {
-		dev_dbg(priv->port.dev, "%s:X character send %02x (%lu)\n",
-			__func__, port->x_char, jiffies);
-		buf[0] = port->x_char;
-		port->x_char = 0;
-		ret = 1;
-	}
-
-	return ret;
-}
-
 static int dma_push_rx(struct eg20t_port *priv, int size)
 {
 	int room;

@@ -889,9 +873,10 @@ static unsigned int handle_tx(struct eg20t_port *priv)
 
 	fifo_size = max(priv->fifo_size, 1);
 	tx_empty = 1;
-	if (pop_tx_x(priv, xmit->buf)) {
-		pch_uart_hal_write(priv, xmit->buf, 1);
+	if (port->x_char) {
+		pch_uart_hal_write(priv, &port->x_char, 1);
 		port->icount.tx++;
+		port->x_char = 0;
 		tx_empty = 0;
 		fifo_size--;
 	}

@@ -948,9 +933,11 @@ static unsigned int dma_handle_tx(struct eg20t_port *priv)
 	}
 
 	fifo_size = max(priv->fifo_size, 1);
-	if (pop_tx_x(priv, xmit->buf)) {
-		pch_uart_hal_write(priv, xmit->buf, 1);
+
+	if (port->x_char) {
+		pch_uart_hal_write(priv, &port->x_char, 1);
 		port->icount.tx++;
+		port->x_char = 0;
 		fifo_size--;
 	}
Signature · 1 line
2.36.1