[3.13.y-ckt stable] Patch "8250: use callbacks to access UART_DLL/UART_DLM" has been added to the 3.13.y-ckt tree

[Kamal Mostafa]

This is a note to let you know that I have just added a patch titled

    8250: use callbacks to access UART_DLL/UART_DLM

to the linux-3.13.y-queue branch of the 3.13.y-ckt extended stable tree 
which can be found at:

    http://kernel.ubuntu.com/git/ubuntu/linux.git/log/?h=linux-3.13.y-queue

This patch is scheduled to be released in version 3.13.11-ckt38.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.13.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

---8<------------------------------------------------------------

>From 583770a1903cc434dfc74f4271e39530450caf49 Mon Sep 17 00:00:00 2001
From: Sebastian Frias <sf84 at laposte.net>
Date: Fri, 18 Dec 2015 17:40:05 +0100
Subject: 8250: use callbacks to access UART_DLL/UART_DLM

commit 0b41ce991052022c030fd868e03877700220b090 upstream.

Some UART HW has a single register combining UART_DLL/UART_DLM
(this was probably forgotten in the change that introduced the
callbacks, commit b32b19b8ffc05cbd3bf91c65e205f6a912ca15d9)

Fixes: b32b19b8ffc0 ("[SERIAL] 8250: set divisor register correctly ...")

Signed-off-by: Sebastian Frias <sf84 at laposte.net>
Reviewed-by: Peter Hurley <peter at hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh at linuxfoundation.org>
[ kamal: backport to 4.2-stable: applies to 8250_core.c ]
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 drivers/tty/serial/8250/8250_core.c | 18 ++++++------------
 1 file changed, 6 insertions(+), 12 deletions(-)

diff --git a/drivers/tty/serial/8250/8250_core.c b/drivers/tty/serial/8250/8250_core.c
index 78abb19..19ef131 100644
--- a/drivers/tty/serial/8250/8250_core.c
+++ b/drivers/tty/serial/8250/8250_core.c
@@ -686,22 +686,16 @@ static int size_fifo(struct uart_8250_port *up)
  */
 static unsigned int autoconfig_read_divisor_id(struct uart_8250_port *p)
 {
-	unsigned char old_dll, old_dlm, old_lcr;
-	unsigned int id;
+	unsigned char old_lcr;
+	unsigned int id, old_dl;

 	old_lcr = serial_in(p, UART_LCR);
 	serial_out(p, UART_LCR, UART_LCR_CONF_MODE_A);
+	old_dl = serial_dl_read(p);
+	serial_dl_write(p, 0);
+	id = serial_dl_read(p);
+	serial_dl_write(p, old_dl);

-	old_dll = serial_in(p, UART_DLL);
-	old_dlm = serial_in(p, UART_DLM);
-
-	serial_out(p, UART_DLL, 0);
-	serial_out(p, UART_DLM, 0);
-
-	id = serial_in(p, UART_DLL) | serial_in(p, UART_DLM) << 8;
-
-	serial_out(p, UART_DLL, old_dll);
-	serial_out(p, UART_DLM, old_dlm);
 	serial_out(p, UART_LCR, old_lcr);

 	return id;
--
2.7.4