linux-kernel - [PATCH 4.9 21/25] tty: serial: 8250: Revert NXP SC16C2552 workaround

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Message-Id: <20180821055126.013171549@linuxfoundation.org>
Date:   Tue, 21 Aug 2018 08:21:35 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Mark Hounschell <dmarkh@....rr.com>
Subject: [PATCH 4.9 21/25] tty: serial: 8250: Revert NXP SC16C2552 workaround

4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Mark <dmarkh@....rr.com>

commit 47ac76662ca9c5852fd353093f19de3ae85f2e66 upstream.

Revert commit ecb988a3b7985913d1f0112f66667cdd15e40711: tty: serial:
8250: 8250_core: NXP SC16C2552 workaround

The above commit causes userland application to no longer write
correctly its first write to a dumb terminal connected to /dev/ttyS0.
This commit seems to be the culprit. It's as though the TX FIFO is being
reset during that write. What should be displayed is:

PSW 80000000 INST 00000000                           HALT
//

What is displayed is some variation of:

T 00000000           HAL//

Reverting this commit via this patch fixes my problem.

Signed-off-by: Mark Hounschell <dmarkh@....rr.com>
Fixes: ecb988a3b798 ("tty: serial: 8250: 8250_core: NXP SC16C2552 workaround")
Cc: stable <stable@...r.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/tty/serial/8250/8250_port.c |    3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

--- a/drivers/tty/serial/8250/8250_port.c
+++ b/drivers/tty/serial/8250/8250_port.c
@@ -83,8 +83,7 @@ static const struct serial8250_config ua
 		.name		= "16550A",
 		.fifo_size	= 16,
 		.tx_loadsz	= 16,
-		.fcr		= UART_FCR_ENABLE_FIFO | UART_FCR_R_TRIG_10 |
-				  UART_FCR_CLEAR_RCVR | UART_FCR_CLEAR_XMIT,
+		.fcr		= UART_FCR_ENABLE_FIFO | UART_FCR_R_TRIG_10,
 		.rxtrig_bytes	= {1, 4, 8, 14},
 		.flags		= UART_CAP_FIFO,
 	},