Hi Greg,

Sorry, please don't apply the patch to stable kernels. I tried to add "linux,rs485-enabled-at-boot-time" support for this driver yesterday and found this patch is not correct, I will send a patch to revert this patch from the mainline kernel.

Thanks,

Hui.

On 4/1/22 18:38, gregkh@linuxfoundation.org wrote:

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

 serial: sc16is7xx: Clear RS485 bits in the shutdown

to the 4.9-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...

The filename of the patch is: serial-sc16is7xx-clear-rs485-bits-in-the-shutdown.patch and it can be found in the queue-4.9 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 927728a34f11b5a27f4610bdb7068317d6fdc72a Mon Sep 17 00:00:00 2001

From: Hui Wang hui.wang@canonical.com Date: Tue, 8 Mar 2022 19:00:42 +0800 Subject: serial: sc16is7xx: Clear RS485 bits in the shutdown

From: Hui Wang hui.wang@canonical.com

commit 927728a34f11b5a27f4610bdb7068317d6fdc72a upstream.

We tested RS485 function on an EVB which has SC16IS752, after finishing the test, we started the RS232 function test, but found the RTS is still working in the RS485 mode.

That is because both startup and shutdown call port_update() to set the EFCR_REG, this will not clear the RS485 bits once the bits are set in the reconf_rs485(). To fix it, clear the RS485 bits in shutdown.

Cc: stable@vger.kernel.org Signed-off-by: Hui Wang hui.wang@canonical.com Link: https://lore.kernel.org/r/20220308110042.108451-1-hui.wang@canonical.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org

---

drivers/tty/serial/sc16is7xx.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-)

--- a/drivers/tty/serial/sc16is7xx.c +++ b/drivers/tty/serial/sc16is7xx.c @@ -1055,10 +1055,12 @@ static void sc16is7xx_shutdown(struct ua /* Disable all interrupts */ sc16is7xx_port_write(port, SC16IS7XX_IER_REG, 0);

• /* Disable TX/RX */

• /* Disable TX/RX, clear auto RS485 and RTS invert */ sc16is7xx_port_update(port, SC16IS7XX_EFCR_REG, SC16IS7XX_EFCR_RXDISABLE_BIT |

• 	      SC16IS7XX_EFCR_TXDISABLE_BIT,
  

• 	      SC16IS7XX_EFCR_TXDISABLE_BIT |
  

• 	      SC16IS7XX_EFCR_AUTO_RS485_BIT |
  

• 	      SC16IS7XX_EFCR_RTS_INVERT_BIT,
        SC16IS7XX_EFCR_RXDISABLE_BIT |
        SC16IS7XX_EFCR_TXDISABLE_BIT);
  

Patches currently in stable-queue which might be from hui.wang@canonical.com are

queue-4.9/serial-sc16is7xx-clear-rs485-bits-in-the-shutdown.patch