From: Thomas Gleixner <tglx@linutronix.de>
Date: Thu, 14 Sep 2023 20:44:07 +0206
Subject: [PATCH 050/134] serial: rda: Use port lock wrappers
Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/6.6/older/patches-6.6.7-rt18.tar.xz

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.

To avoid adding this functionality to all UART drivers, wrap the
spin_[un]lock*() invocations for uart_port::lock into helper functions
which just contain the spin_[un]lock*() invocations for now. In a
subsequent step these helpers will gain the console synchronization
mechanisms.

Converted with coccinelle. No functional change.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Link: https://lore.kernel.org/r/20230914183831.587273-51-john.ogness@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
 drivers/tty/serial/rda-uart.c |   34 +++++++++++++++++-----------------
 1 file changed, 17 insertions(+), 17 deletions(-)

--- a/drivers/tty/serial/rda-uart.c
+++ b/drivers/tty/serial/rda-uart.c
@@ -139,12 +139,12 @@ static unsigned int rda_uart_tx_empty(st
 	unsigned int ret;
 	u32 val;
 
-	spin_lock_irqsave(&port->lock, flags);
+	uart_port_lock_irqsave(port, &flags);
 
 	val = rda_uart_read(port, RDA_UART_STATUS);
 	ret = (val & RDA_UART_TX_FIFO_MASK) ? TIOCSER_TEMT : 0;
 
-	spin_unlock_irqrestore(&port->lock, flags);
+	uart_port_unlock_irqrestore(port, flags);
 
 	return ret;
 }
@@ -246,7 +246,7 @@ static void rda_uart_set_termios(struct
 	unsigned int baud;
 	u32 irq_mask;
 
-	spin_lock_irqsave(&port->lock, flags);
+	uart_port_lock_irqsave(port, &flags);
 
 	baud = uart_get_baud_rate(port, termios, old, 9600, port->uartclk / 4);
 	rda_uart_change_baudrate(rda_port, baud);
@@ -325,7 +325,7 @@ static void rda_uart_set_termios(struct
 	/* update the per-port timeout */
 	uart_update_timeout(port, termios->c_cflag, baud);
 
-	spin_unlock_irqrestore(&port->lock, flags);
+	uart_port_unlock_irqrestore(port, flags);
 }
 
 static void rda_uart_send_chars(struct uart_port *port)
@@ -408,7 +408,7 @@ static irqreturn_t rda_interrupt(int irq
 	unsigned long flags;
 	u32 val, irq_mask;
 
-	spin_lock_irqsave(&port->lock, flags);
+	uart_port_lock_irqsave(port, &flags);
 
 	/* Clear IRQ cause */
 	val = rda_uart_read(port, RDA_UART_IRQ_CAUSE);
@@ -425,7 +425,7 @@ static irqreturn_t rda_interrupt(int irq
 		rda_uart_send_chars(port);
 	}
 
-	spin_unlock_irqrestore(&port->lock, flags);
+	uart_port_unlock_irqrestore(port, flags);
 
 	return IRQ_HANDLED;
 }
@@ -436,16 +436,16 @@ static int rda_uart_startup(struct uart_
 	int ret;
 	u32 val;
 
-	spin_lock_irqsave(&port->lock, flags);
+	uart_port_lock_irqsave(port, &flags);
 	rda_uart_write(port, 0, RDA_UART_IRQ_MASK);
-	spin_unlock_irqrestore(&port->lock, flags);
+	uart_port_unlock_irqrestore(port, flags);
 
 	ret = request_irq(port->irq, rda_interrupt, IRQF_NO_SUSPEND,
 			  "rda-uart", port);
 	if (ret)
 		return ret;
 
-	spin_lock_irqsave(&port->lock, flags);
+	uart_port_lock_irqsave(port, &flags);
 
 	val = rda_uart_read(port, RDA_UART_CTRL);
 	val |= RDA_UART_ENABLE;
@@ -456,7 +456,7 @@ static int rda_uart_startup(struct uart_
 	val |= (RDA_UART_RX_DATA_AVAILABLE | RDA_UART_RX_TIMEOUT);
 	rda_uart_write(port, val, RDA_UART_IRQ_MASK);
 
-	spin_unlock_irqrestore(&port->lock, flags);
+	uart_port_unlock_irqrestore(port, flags);
 
 	return 0;
 }
@@ -466,7 +466,7 @@ static void rda_uart_shutdown(struct uar
 	unsigned long flags;
 	u32 val;
 
-	spin_lock_irqsave(&port->lock, flags);
+	uart_port_lock_irqsave(port, &flags);
 
 	rda_uart_stop_tx(port);
 	rda_uart_stop_rx(port);
@@ -475,7 +475,7 @@ static void rda_uart_shutdown(struct uar
 	val &= ~RDA_UART_ENABLE;
 	rda_uart_write(port, val, RDA_UART_CTRL);
 
-	spin_unlock_irqrestore(&port->lock, flags);
+	uart_port_unlock_irqrestore(port, flags);
 }
 
 static const char *rda_uart_type(struct uart_port *port)
@@ -515,7 +515,7 @@ static void rda_uart_config_port(struct
 		rda_uart_request_port(port);
 	}
 
-	spin_lock_irqsave(&port->lock, irq_flags);
+	uart_port_lock_irqsave(port, &irq_flags);
 
 	/* Clear mask, so no surprise interrupts. */
 	rda_uart_write(port, 0, RDA_UART_IRQ_MASK);
@@ -523,7 +523,7 @@ static void rda_uart_config_port(struct
 	/* Clear status register */
 	rda_uart_write(port, 0, RDA_UART_STATUS);
 
-	spin_unlock_irqrestore(&port->lock, irq_flags);
+	uart_port_unlock_irqrestore(port, irq_flags);
 }
 
 static void rda_uart_release_port(struct uart_port *port)
@@ -597,9 +597,9 @@ static void rda_uart_port_write(struct u
 	if (port->sysrq) {
 		locked = 0;
 	} else if (oops_in_progress) {
-		locked = spin_trylock(&port->lock);
+		locked = uart_port_trylock(port);
 	} else {
-		spin_lock(&port->lock);
+		uart_port_lock(port);
 		locked = 1;
 	}
 
@@ -615,7 +615,7 @@ static void rda_uart_port_write(struct u
 	rda_uart_write(port, old_irq_mask, RDA_UART_IRQ_MASK);
 
 	if (locked)
-		spin_unlock(&port->lock);
+		uart_port_unlock(port);
 
 	local_irq_restore(flags);
 }
