linux-kernel - [PATCH] serial: sc16is7xx: remove useless enable of enhanced features

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Message-Id: <20251006142002.177475-1-hugo@hugovil.com>
Date: Mon,  6 Oct 2025 10:20:02 -0400
From: Hugo Villeneuve <hugo@...ovil.com>
To: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Jiri Slaby <jirislaby@...nel.org>,
	Florian Vallee <fvallee@...rea.fr>
Cc: hugo@...ovil.com,
	Hugo Villeneuve <hvilleneuve@...onoff.com>,
	stable@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	linux-serial@...r.kernel.org
Subject: [PATCH] serial: sc16is7xx: remove useless enable of enhanced features

From: Hugo Villeneuve <hvilleneuve@...onoff.com>

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@...r.kernel.org
Signed-off-by: Hugo Villeneuve <hvilleneuve@...onoff.com>
---
This patch was originally part of this series:
https://lore.kernel.org/linux-serial/20251002145738.3250272-1-hugo@hugovil.com/raw
and it is now separate as suggested by Greg to facilitate stable backporting.
---
 drivers/tty/serial/sc16is7xx.c | 7 -------
 1 file changed, 7 deletions(-)

diff --git a/drivers/tty/serial/sc16is7xx.c b/drivers/tty/serial/sc16is7xx.c
index 1a2c4c14f6aac..c7435595dce13 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,

base-commit: fd94619c43360eb44d28bd3ef326a4f85c600a07
-- 
2.39.5