FAILED: patch "[PATCH] mailbox: altera: shut down RX polling timer on channel teardown" failed to apply to 5.15-stable tree

[Sasha Levin <sashal@kernel.org>]

The patch below does not apply to the 5.15-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-5.15.y
git checkout FETCH_HEAD
git cherry-pick -x 0cf10e65639cba32d05994f85e6a8f08dd0ffe08
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '20261107060413-failed-5.15-0cf10e65639c@kernel.org' --subject-prefix 'PATCH 5.15.y' 'HEAD^..'

Thanks,
Sasha

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

From 0cf10e65639cba32d05994f85e6a8f08dd0ffe08 Mon Sep 17 00:00:00 2001
From: Runyu Xiao <runyu.xiao@seu.edu.cn>
Date: Fri, 4 Sep 2026 14:19:39 +0800
Subject: [PATCH] mailbox: altera: shut down RX polling timer on channel
 teardown

The RX polling callback unconditionally rearms the timer after it
processes mailbox data.  altera_mbox_shutdown() uses
timer_delete_sync(), which waits for a running callback but does not
prevent that callback from rearming the timer after the deletion.

Use timer_shutdown_sync() for the final polling teardown so the timer
cannot be queued again while the mailbox channel is being released.
The timer is reinitialized with timer_setup() on a later channel startup,
so polling mode remains reusable.

Fixes: f62092f6d77d ("mailbox: Add Altera mailbox driver")
Cc: stable@vger.kernel.org
Assisted-by: Codex:GPT-5
Signed-off-by: Runyu Xiao <runyu.xiao@seu.edu.cn>
Signed-off-by: Jassi Brar <jassisinghbrar@gmail.com>
---
 drivers/mailbox/mailbox-altera.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/mailbox/mailbox-altera.c b/drivers/mailbox/mailbox-altera.c
index 17278c2571d34..7cb91413ef7fc 100644
--- a/drivers/mailbox/mailbox-altera.c
+++ b/drivers/mailbox/mailbox-altera.c
@@ -270,7 +270,7 @@ static void altera_mbox_shutdown(struct mbox_chan *chan)
 		writel_relaxed(~0, mbox->mbox_base + MAILBOX_INTMASK_REG);
 		free_irq(mbox->irq, chan);
 	} else if (!mbox->is_sender) {
-		timer_delete_sync(&mbox->rxpoll_timer);
+		timer_shutdown_sync(&mbox->rxpoll_timer);
 	}
 }
 
-- 
2.53.0