FAILED: patch "[PATCH] serial: sc16is7xx: remove useless enable of enhanced features" failed to apply to 5.4-stable tree

[<gregkh@linuxfoundation.org>]

The patch below does not apply to the 5.4-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.4.y
git checkout FETCH_HEAD
git cherry-pick -x 1c05bf6c0262f946571a37678250193e46b1ff0f
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2025102740-dumpster-clapper-519c@gregkh' --subject-prefix 'PATCH 5.4.y' HEAD^..

Possible dependencies:



thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 1c05bf6c0262f946571a37678250193e46b1ff0f Mon Sep 17 00:00:00 2001
From: Hugo Villeneuve <hvilleneuve@dimonoff.com>
Date: Mon, 6 Oct 2025 10:20:02 -0400
Subject: [PATCH] serial: sc16is7xx: remove useless enable of enhanced features

Commit 43c51bb573aa ("sc16is7xx: make sure device is in suspend once
probed") permanently enabled access to the enhanced features in
sc16is7xx_probe(), and it is never disabled after that.

Therefore, remove re-enable of enhanced features in
sc16is7xx_set_baud(). This eliminates a potential useless read + write
cycle each time the baud rate is reconfigured.

Fixes: 43c51bb573aa ("sc16is7xx: make sure device is in suspend once probed")
Cc: stable <stable@kernel.org>
Signed-off-by: Hugo Villeneuve <hvilleneuve@dimonoff.com>
Link: https://patch.msgid.link/20251006142002.177475-1-hugo@hugovil.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/serial/sc16is7xx.c b/drivers/tty/serial/sc16is7xx.c
index 1a2c4c14f6aa..c7435595dce1 100644
--- a/drivers/tty/serial/sc16is7xx.c
+++ b/drivers/tty/serial/sc16is7xx.c
@@ -588,13 +588,6 @@ static int sc16is7xx_set_baud(struct uart_port *port, int baud)
 		div /= prescaler;
 	}
 
-	/* Enable enhanced features */
-	sc16is7xx_efr_lock(port);
-	sc16is7xx_port_update(port, SC16IS7XX_EFR_REG,
-			      SC16IS7XX_EFR_ENABLE_BIT,
-			      SC16IS7XX_EFR_ENABLE_BIT);
-	sc16is7xx_efr_unlock(port);
-
 	/* If bit MCR_CLKSEL is set, the divide by 4 prescaler is activated. */
 	sc16is7xx_port_update(port, SC16IS7XX_MCR_REG,
 			      SC16IS7XX_MCR_CLKSEL_BIT,