Patch "BUG: atmel_serial: Interrupts not disabled on close" has been added to the 4.8-stable tree

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

    BUG: atmel_serial: Interrupts not disabled on close

to the 4.8-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:
bug-atmel_serial-interrupts-not-disabled-on-close.patch
and it can be found in the queue-4.8 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Richard Genoud <[email protected]>
Date: Mon, 12 Sep 2016 15:34:41 +0200
Subject: BUG: atmel_serial: Interrupts not disabled on close
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From: Richard Genoud <[email protected]>

commit 0ae9fdefb6c37237d826d6195e27810ffcc0b6e0 upstream.

Since commit 18dfef9c7f87 ("serial: atmel: convert to irq handling provided mctrl-gpio"), interrupts from GPIOs are not disabled any more when the serial port is closed, leading to an oops when the one of the input pin is toggled (CTS/DSR/DCD/RNG).

This is only the case if those pins are used as GPIOs, i.e. declared like that:

usart1: serial@f8020000 {
        /* CTS and DTS will be handled by GPIO */
        status = "okay";
        rts-gpios = <&pioB 17 GPIO_ACTIVE_LOW>;
        cts-gpios = <&pioB 16 GPIO_ACTIVE_LOW>;
        dtr-gpios = <&pioB 14 GPIO_ACTIVE_LOW>;
        dsr-gpios = <&pioC 31 GPIO_ACTIVE_LOW>;
        rng-gpios = <&pioB 12 GPIO_ACTIVE_LOW>;
        dcd-gpios = <&pioB 15 GPIO_ACTIVE_LOW>;
};

That's because modem interrupts used to be freed in atmel_shutdown(). After commit 18dfef9c7f87 ("serial: atmel: convert to irq handling provided mctrl-gpio"), this code was just removed.
Calling atmel_disable_ms() disables the interrupts and everything works fine again.

Tested on at91sam9g35-cm

(This patch doesn't apply on -stable kernels, fixes for 4.4 and 4.7 will be sent after this one is applied.)

---
 drivers/tty/serial/atmel_serial.c |    5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

@@ -1929,6 +1929,9 @@ static void atmel_shutdown(struct uart_p
 {
 	struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);
 
+	/* Disable modem control lines interrupts */
+	atmel_disable_ms(port);
+
 	/* Disable interrupts at device level */
 	atmel_uart_writel(port, ATMEL_US_IDR, -1);
 

@@ -1979,8 +1982,6 @@ static void atmel_shutdown(struct uart_p
 	 */
 	free_irq(port->irq, port);
 
-	atmel_port->ms_irq_enabled = false;
-
 	atmel_flush_buffer(port);
 }
 

Patches currently in stable-queue which might be from [email protected] are

queue-4.8/bug-atmel_serial-interrupts-not-disabled-on-close.patch