FAILED: patch "[PATCH] serial: sc16is7xx: declare MCR and IER as volatile registers" failed to apply to 5.10-stable tree

FAILED: patch "[PATCH] serial: sc16is7xx: declare MCR and IER as volatile registers" failed to apply to 5.10-stable tree

[Sasha Levin]

The patch below does not apply to the 5.10-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-5.10.y
git checkout FETCH_HEAD
git cherry-pick -x 1c41d09dcd07ee9648e20aa8238e404c2e6a12fb
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '20261107062211-failed-5.10-1c41d09dcd07@kernel.org' --subject-prefix 'PATCH 5.10.y' 'HEAD^..'

Thanks,
Sasha

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

From 1c41d09dcd07ee9648e20aa8238e404c2e6a12fb Mon Sep 17 00:00:00 2001
From: Hugo Villeneuve <hvilleneuve@dimonoff.com>
Date: Tue, 6 Oct 2026 15:25:37 -0400
Subject: [PATCH] serial: sc16is7xx: declare MCR and IER as volatile registers

MCR register has the same address as XON1 register.
IER register has the same address as DLH register.

Which register is accessed depends on bits configuration in some
other registers.

To prevent potential access errors, declare MCR and IER as volatile
registers.

Fixes: dfeae619d781 ("serial: sc16is7xx")
Cc: stable@kernel.org
Signed-off-by: Hugo Villeneuve <hvilleneuve@dimonoff.com>
Link: https://patch.msgid.link/20261006192540.234402-1-hugo@hugovil.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/tty/serial/sc16is7xx.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/tty/serial/sc16is7xx.c b/drivers/tty/serial/sc16is7xx.c
index 7ddc8a38adab4..fba5885595957 100644
--- a/drivers/tty/serial/sc16is7xx.c
+++ b/drivers/tty/serial/sc16is7xx.c
@@ -501,7 +501,9 @@ static bool sc16is7xx_regmap_volatile(struct device *dev, unsigned int reg)
 {
 	switch (reg) {
 	case SC16IS7XX_RHR_REG: /* Shared address space with THR & DLL */
+	case SC16IS7XX_IER_REG: /* Shared address space with DLH */
 	case SC16IS7XX_IIR_REG: /* Shared address space with FCR & EFR */
+	case SC16IS7XX_MCR_REG: /* Shared address space with XON1 */
 	case SC16IS7XX_LSR_REG: /* Shared address space with XON2 */
 	case SC16IS7XX_MSR_REG: /* Shared address space with TCR & XOFF1 */
 	case SC16IS7XX_SPR_REG: /* Shared address space with TLR & XOFF2 */
-- 
2.53.0

[PATCH 5.10.y] serial: sc16is7xx: declare MCR and IER as volatile registers

[Sasha Levin]

From: Hugo Villeneuve <hvilleneuve@dimonoff.com>

[ Upstream commit 1c41d09dcd07ee9648e20aa8238e404c2e6a12fb ]

MCR register has the same address as XON1 register.
IER register has the same address as DLH register.

Which register is accessed depends on bits configuration in some
other registers.

To prevent potential access errors, declare MCR and IER as volatile
registers.

Fixes: dfeae619d781 ("serial: sc16is7xx")
Cc: stable@kernel.org
Signed-off-by: Hugo Villeneuve <hvilleneuve@dimonoff.com>
Link: https://patch.msgid.link/20261006192540.234402-1-hugo@hugovil.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
[ sashal: adjusted context to match the existing switch using reg >> SC16IS7XX_REG_SHIFT ]
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/tty/serial/sc16is7xx.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/tty/serial/sc16is7xx.c b/drivers/tty/serial/sc16is7xx.c
index e177df2c4ea22..1934fce0fa732 100644
--- a/drivers/tty/serial/sc16is7xx.c
+++ b/drivers/tty/serial/sc16is7xx.c
@@ -467,7 +467,9 @@ static bool sc16is7xx_regmap_volatile(struct device *dev, unsigned int reg)
 {
 	switch (reg >> SC16IS7XX_REG_SHIFT) {
 	case SC16IS7XX_RHR_REG:
+	case SC16IS7XX_IER_REG: /* Shared address space with DLH */
 	case SC16IS7XX_IIR_REG:
+	case SC16IS7XX_MCR_REG: /* Shared address space with XON1 */
 	case SC16IS7XX_LSR_REG:
 	case SC16IS7XX_MSR_REG:
 	case SC16IS7XX_TXLVL_REG:
-- 
2.53.0