From: Thomas Gleixner <tglx@linutronix.de>
Date: Thu, 14 Sep 2023 20:43:36 +0206
Subject: [PATCH 019/134] serial: ar933x: 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/20230914183831.587273-20-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/ar933x_uart.c |   26 +++++++++++++-------------
 1 file changed, 13 insertions(+), 13 deletions(-)

--- a/drivers/tty/serial/ar933x_uart.c
+++ b/drivers/tty/serial/ar933x_uart.c
@@ -133,9 +133,9 @@ static unsigned int ar933x_uart_tx_empty
 	unsigned long flags;
 	unsigned int rdata;
 
-	spin_lock_irqsave(&up->port.lock, flags);
+	uart_port_lock_irqsave(&up->port, &flags);
 	rdata = ar933x_uart_read(up, AR933X_UART_DATA_REG);
-	spin_unlock_irqrestore(&up->port.lock, flags);
+	uart_port_unlock_irqrestore(&up->port, flags);
 
 	return (rdata & AR933X_UART_DATA_TX_CSR) ? 0 : TIOCSER_TEMT;
 }
@@ -220,14 +220,14 @@ static void ar933x_uart_break_ctl(struct
 		container_of(port, struct ar933x_uart_port, port);
 	unsigned long flags;
 
-	spin_lock_irqsave(&up->port.lock, flags);
+	uart_port_lock_irqsave(&up->port, &flags);
 	if (break_state == -1)
 		ar933x_uart_rmw_set(up, AR933X_UART_CS_REG,
 				    AR933X_UART_CS_TX_BREAK);
 	else
 		ar933x_uart_rmw_clear(up, AR933X_UART_CS_REG,
 				      AR933X_UART_CS_TX_BREAK);
-	spin_unlock_irqrestore(&up->port.lock, flags);
+	uart_port_unlock_irqrestore(&up->port, flags);
 }
 
 /*
@@ -318,7 +318,7 @@ static void ar933x_uart_set_termios(stru
 	 * Ok, we're now changing the port state. Do it with
 	 * interrupts disabled.
 	 */
-	spin_lock_irqsave(&up->port.lock, flags);
+	uart_port_lock_irqsave(&up->port, &flags);
 
 	/* disable the UART */
 	ar933x_uart_rmw_clear(up, AR933X_UART_CS_REG,
@@ -352,7 +352,7 @@ static void ar933x_uart_set_termios(stru
 			AR933X_UART_CS_IF_MODE_M << AR933X_UART_CS_IF_MODE_S,
 			AR933X_UART_CS_IF_MODE_DCE << AR933X_UART_CS_IF_MODE_S);
 
-	spin_unlock_irqrestore(&up->port.lock, flags);
+	uart_port_unlock_irqrestore(&up->port, flags);
 
 	if (tty_termios_baud_rate(new))
 		tty_termios_encode_baud_rate(new, baud, baud);
@@ -450,7 +450,7 @@ static irqreturn_t ar933x_uart_interrupt
 	if ((status & AR933X_UART_CS_HOST_INT) == 0)
 		return IRQ_NONE;
 
-	spin_lock(&up->port.lock);
+	uart_port_lock(&up->port);
 
 	status = ar933x_uart_read(up, AR933X_UART_INT_REG);
 	status &= ar933x_uart_read(up, AR933X_UART_INT_EN_REG);
@@ -468,7 +468,7 @@ static irqreturn_t ar933x_uart_interrupt
 		ar933x_uart_tx_chars(up);
 	}
 
-	spin_unlock(&up->port.lock);
+	uart_port_unlock(&up->port);
 
 	return IRQ_HANDLED;
 }
@@ -485,7 +485,7 @@ static int ar933x_uart_startup(struct ua
 	if (ret)
 		return ret;
 
-	spin_lock_irqsave(&up->port.lock, flags);
+	uart_port_lock_irqsave(&up->port, &flags);
 
 	/* Enable HOST interrupts */
 	ar933x_uart_rmw_set(up, AR933X_UART_CS_REG,
@@ -498,7 +498,7 @@ static int ar933x_uart_startup(struct ua
 	/* Enable RX interrupts */
 	ar933x_uart_start_rx_interrupt(up);
 
-	spin_unlock_irqrestore(&up->port.lock, flags);
+	uart_port_unlock_irqrestore(&up->port, flags);
 
 	return 0;
 }
@@ -632,9 +632,9 @@ static void ar933x_uart_console_write(st
 	if (up->port.sysrq)
 		locked = 0;
 	else if (oops_in_progress)
-		locked = spin_trylock(&up->port.lock);
+		locked = uart_port_trylock(&up->port);
 	else
-		spin_lock(&up->port.lock);
+		uart_port_lock(&up->port);
 
 	/*
 	 * First save the IER then disable the interrupts
@@ -654,7 +654,7 @@ static void ar933x_uart_console_write(st
 	ar933x_uart_write(up, AR933X_UART_INT_REG, AR933X_UART_INT_ALLINTS);
 
 	if (locked)
-		spin_unlock(&up->port.lock);
+		uart_port_unlock(&up->port);
 
 	local_irq_restore(flags);
 }
