--- /dev/null
+From 0e28923320be00e96ab501d0f264db598d1bad19 Mon Sep 17 00:00:00 2001
+From: Sasha Levin <sashal@kernel.org>
+Date: Thu, 14 Sep 2023 20:43:18 +0206
+Subject: serial: core: Provide port lock wrappers
+MIME-Version: 1.0
+Content-Type: text/plain; charset=UTF-8
+Content-Transfer-Encoding: 8bit
+
+From: Thomas Gleixner <tglx@linutronix.de>
+
+[ Upstream commit b0af4bcb49464c221ad5f95d40f2b1b252ceedcc ]
+
+When a serial port is used for kernel console output, then all
+modifications to the UART registers which are done from other contexts,
+e.g. getty, termios, are interference points for the kernel console.
+
+So far this has been ignored and the printk output is based on the
+principle of hope. The rework of the console infrastructure which aims to
+support threaded and atomic consoles, requires to mark sections which
+modify the UART registers as unsafe. This allows the atomic write function
+to make informed decisions and eventually to restore operational state. It
+also allows to prevent the regular UART code from modifying UART registers
+while printk output is in progress.
+
+All modifications of UART registers are guarded by the UART port lock,
+which provides an obvious synchronization point with the console
+infrastructure.
+
+Provide wrapper functions for spin_[un]lock*(port->lock) invocations so
+that the console mechanics can be applied later on at a single place and
+does not require to copy the same logic all over the drivers.
+
+Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
+Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
+Signed-off-by: John Ogness <john.ogness@linutronix.de>
+Link: https://lore.kernel.org/r/20230914183831.587273-2-john.ogness@linutronix.de
+Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
+Stable-dep-of: 54c4ec5f8c47 ("serial: mxs-auart: add spinlock around changing cts state")
+Signed-off-by: Sasha Levin <sashal@kernel.org>
+---
+ include/linux/serial_core.h | 79 +++++++++++++++++++++++++++++++++++++
+ 1 file changed, 79 insertions(+)
+
+diff --git a/include/linux/serial_core.h b/include/linux/serial_core.h
+index 46a21984c0b22..8c136a6a28c04 100644
+--- a/include/linux/serial_core.h
++++ b/include/linux/serial_core.h
+@@ -260,6 +260,85 @@ struct uart_port {
+ void *private_data; /* generic platform data pointer */
+ };
+
++/**
++ * uart_port_lock - Lock the UART port
++ * @up: Pointer to UART port structure
++ */
++static inline void uart_port_lock(struct uart_port *up)
++{
++ spin_lock(&up->lock);
++}
++
++/**
++ * uart_port_lock_irq - Lock the UART port and disable interrupts
++ * @up: Pointer to UART port structure
++ */
++static inline void uart_port_lock_irq(struct uart_port *up)
++{
++ spin_lock_irq(&up->lock);
++}
++
++/**
++ * uart_port_lock_irqsave - Lock the UART port, save and disable interrupts
++ * @up: Pointer to UART port structure
++ * @flags: Pointer to interrupt flags storage
++ */
++static inline void uart_port_lock_irqsave(struct uart_port *up, unsigned long *flags)
++{
++ spin_lock_irqsave(&up->lock, *flags);
++}
++
++/**
++ * uart_port_trylock - Try to lock the UART port
++ * @up: Pointer to UART port structure
++ *
++ * Returns: True if lock was acquired, false otherwise
++ */
++static inline bool uart_port_trylock(struct uart_port *up)
++{
++ return spin_trylock(&up->lock);
++}
++
++/**
++ * uart_port_trylock_irqsave - Try to lock the UART port, save and disable interrupts
++ * @up: Pointer to UART port structure
++ * @flags: Pointer to interrupt flags storage
++ *
++ * Returns: True if lock was acquired, false otherwise
++ */
++static inline bool uart_port_trylock_irqsave(struct uart_port *up, unsigned long *flags)
++{
++ return spin_trylock_irqsave(&up->lock, *flags);
++}
++
++/**
++ * uart_port_unlock - Unlock the UART port
++ * @up: Pointer to UART port structure
++ */
++static inline void uart_port_unlock(struct uart_port *up)
++{
++ spin_unlock(&up->lock);
++}
++
++/**
++ * uart_port_unlock_irq - Unlock the UART port and re-enable interrupts
++ * @up: Pointer to UART port structure
++ */
++static inline void uart_port_unlock_irq(struct uart_port *up)
++{
++ spin_unlock_irq(&up->lock);
++}
++
++/**
++ * uart_port_lock_irqrestore - Unlock the UART port, restore interrupts
++ * @up: Pointer to UART port structure
++ * @flags: The saved interrupt flags for restore
++ */
++static inline void uart_port_unlock_irqrestore(struct uart_port *up, unsigned long flags)
++{
++ spin_unlock_irqrestore(&up->lock, flags);
++}
++
+ static inline int serial_port_in(struct uart_port *up, int offset)
+ {
+ return up->serial_in(up, offset);
+--
+2.43.0
+
--- /dev/null
+From 4a1f6aaafbc6a17d570d643d4fc12942a262e198 Mon Sep 17 00:00:00 2001
+From: Sasha Levin <sashal@kernel.org>
+Date: Wed, 20 Mar 2024 12:15:36 +0000
+Subject: serial: mxs-auart: add spinlock around changing cts state
+
+From: Emil Kronborg <emil.kronborg@protonmail.com>
+
+[ Upstream commit 54c4ec5f8c471b7c1137a1f769648549c423c026 ]
+
+The uart_handle_cts_change() function in serial_core expects the caller
+to hold uport->lock. For example, I have seen the below kernel splat,
+when the Bluetooth driver is loaded on an i.MX28 board.
+
+ [ 85.119255] ------------[ cut here ]------------
+ [ 85.124413] WARNING: CPU: 0 PID: 27 at /drivers/tty/serial/serial_core.c:3453 uart_handle_cts_change+0xb4/0xec
+ [ 85.134694] Modules linked in: hci_uart bluetooth ecdh_generic ecc wlcore_sdio configfs
+ [ 85.143314] CPU: 0 PID: 27 Comm: kworker/u3:0 Not tainted 6.6.3-00021-gd62a2f068f92 #1
+ [ 85.151396] Hardware name: Freescale MXS (Device Tree)
+ [ 85.156679] Workqueue: hci0 hci_power_on [bluetooth]
+ (...)
+ [ 85.191765] uart_handle_cts_change from mxs_auart_irq_handle+0x380/0x3f4
+ [ 85.198787] mxs_auart_irq_handle from __handle_irq_event_percpu+0x88/0x210
+ (...)
+
+Cc: stable@vger.kernel.org
+Fixes: 4d90bb147ef6 ("serial: core: Document and assert lock requirements for irq helpers")
+Reviewed-by: Frank Li <Frank.Li@nxp.com>
+Signed-off-by: Emil Kronborg <emil.kronborg@protonmail.com>
+Link: https://lore.kernel.org/r/20240320121530.11348-1-emil.kronborg@protonmail.com
+Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
+Signed-off-by: Sasha Levin <sashal@kernel.org>
+---
+ drivers/tty/serial/mxs-auart.c | 8 ++++++--
+ 1 file changed, 6 insertions(+), 2 deletions(-)
+
+diff --git a/drivers/tty/serial/mxs-auart.c b/drivers/tty/serial/mxs-auart.c
+index b784323a6a7b0..be6c8b9f1606e 100644
+--- a/drivers/tty/serial/mxs-auart.c
++++ b/drivers/tty/serial/mxs-auart.c
+@@ -1122,11 +1122,13 @@ static void mxs_auart_set_ldisc(struct uart_port *port,
+
+ static irqreturn_t mxs_auart_irq_handle(int irq, void *context)
+ {
+- u32 istat;
++ u32 istat, stat;
+ struct mxs_auart_port *s = context;
+ u32 mctrl_temp = s->mctrl_prev;
+- u32 stat = mxs_read(s, REG_STAT);
+
++ uart_port_lock(&s->port);
++
++ stat = mxs_read(s, REG_STAT);
+ istat = mxs_read(s, REG_INTR);
+
+ /* ack irq */
+@@ -1162,6 +1164,8 @@ static irqreturn_t mxs_auart_irq_handle(int irq, void *context)
+ istat &= ~AUART_INTR_TXIS;
+ }
+
++ uart_port_unlock(&s->port);
++
+ return IRQ_HANDLED;
+ }
+
+--
+2.43.0
+
projects / thirdparty / kernel / stable-queue.git / commitdiff
