linux-kernel - [PATCH 07/15] serial: sc16is7xx: declare SPR/TLR/XOFF2 register as volatile

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Message-Id: <20250924153740.806444-8-hugo@hugovil.com>
Date: Wed, 24 Sep 2025 11:37:32 -0400
From: Hugo Villeneuve <hugo@...ovil.com>
To: gregkh@...uxfoundation.org,
	jirislaby@...nel.org,
	fvallee@...rea.fr
Cc: linux-kernel@...r.kernel.org,
	linux-serial@...r.kernel.org,
	hugo@...ovil.com,
	Hugo Villeneuve <hvilleneuve@...onoff.com>
Subject: [PATCH 07/15] serial: sc16is7xx: declare SPR/TLR/XOFF2 register as volatile

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

SPR shares the same address space as TLR and XOFF2. If SPR or TLR were to
be used eventually, this could lead to incorrect read value from the cache.

Prevent this potential bug by declaring SPR/TLR/XOFF2 as volatile.

Signed-off-by: Hugo Villeneuve <hvilleneuve@...onoff.com>
---
 drivers/tty/serial/sc16is7xx.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/tty/serial/sc16is7xx.c b/drivers/tty/serial/sc16is7xx.c
index 4384804a4e228..96ea308013912 100644
--- a/drivers/tty/serial/sc16is7xx.c
+++ b/drivers/tty/serial/sc16is7xx.c
@@ -545,6 +545,7 @@ static bool sc16is7xx_regmap_volatile(struct device *dev, unsigned int reg)
 	case SC16IS7XX_IIR_REG:
 	case SC16IS7XX_LSR_REG:
 	case SC16IS7XX_MSR_REG:
+	case SC16IS7XX_SPR_REG: /* Shared address space with TLR & XOFF2 */
 	case SC16IS7XX_TXLVL_REG:
 	case SC16IS7XX_RXLVL_REG:
 	case SC16IS7XX_IOSTATE_REG:
-- 
2.39.5