Patch "serial: 8250: Check UART_SCR is writable" has been added to the 4.0-stable tree

Patch "serial: 8250: Check UART_SCR is writable" has been added to the 4.0-stable tree

[gregkh]

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

    serial: 8250: Check UART_SCR is writable

to the 4.0-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-8250-check-uart_scr-is-writable.patch
and it can be found in the queue-4.0 subdirectory.

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


>From f01a0bd8921b9d6668d41fae3198970e6318f532 Mon Sep 17 00:00:00 2001
From: Peter Hurley <peter@hurleysoftware.com>
Date: Mon, 9 Mar 2015 14:05:01 -0400
Subject: serial: 8250: Check UART_SCR is writable

From: Peter Hurley <peter@hurleysoftware.com>

commit f01a0bd8921b9d6668d41fae3198970e6318f532 upstream.

Au1x00/RT2800+ doesn't implement the 8250 scratch register (and
this may be true of other h/w currently supported by the 8250 driver);
read back the canary value written to the scratch register to enable
the console h/w restart after resume from system suspend.

Fixes: 4516d50aabedb ("serial: 8250: Use canary to restart console ...")
Reported-by: Mason <slash.tmp@free.fr>
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/tty/serial/8250/8250_core.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/drivers/tty/serial/8250/8250_core.c
+++ b/drivers/tty/serial/8250/8250_core.c
@@ -3444,7 +3444,8 @@ void serial8250_suspend_port(int line)
 	    port->type != PORT_8250) {
 		unsigned char canary = 0xa5;
 		serial_out(up, UART_SCR, canary);
-		up->canary = canary;
+		if (serial_in(up, UART_SCR) == canary)
+			up->canary = canary;
 	}
 
 	uart_suspend_port(&serial8250_reg, port);


Patches currently in stable-queue which might be from peter@hurleysoftware.com are

queue-4.0/serial-8250-check-uart_scr-is-writable.patch