Subject: [PATCH 17/18] serial: pch: Remove eg20t_port::lock.
From: Sebastian Andrzej Siewior <[email-masked]>
Date: Fri, 1 Mar 2024 22:45:30 +0100

The struct eg20t_port has a spinlock_t which is used for locking while
access I/O of the device. Then there is the uart_portlock which is
sometimes and nests within eg20t_port's lock.

The uart_port lock is not used while using the struct in
pch_uart_hal_read() which might be okay. Then both locks are used in
pch_console_write() which looks odd especially the double try_lock part.

All in all it looks like the uart_port's lock could replace eg20t_port's
lock and simplify the code.

Remove eg20t_port::lock and use uart_port's lock for the lock scope.

Link: https://lore.kernel.org/r/[email-masked]
Signed-off-by: Sebastian Andrzej Siewior <[email-masked]>
---
 drivers/tty/serial/pch_uart.c |   26 ++++++--------------------
 1 file changed, 6 insertions(+), 20 deletions(-)

Index: linux-6.8.2-rt10/drivers/tty/serial/pch_uart.c
===================================================================
--- linux-6.8.2-rt10.orig/drivers/tty/serial/pch_uart.c
+++ linux-6.8.2-rt10/drivers/tty/serial/pch_uart.c
@@ -237,9 +237,6 @@ struct eg20t_port {
 
 #define IRQ_NAME_SIZE 17
 	char				irq_name[IRQ_NAME_SIZE];
-
-	/* protect the eg20t_port private structure and io access to membase */
-	spinlock_t lock;
 };
 
 /**
@@ -1013,7 +1010,7 @@ static irqreturn_t pch_uart_interrupt(in
 	int next = 1;
 	u8 msr;
 
-	spin_lock(&priv->lock);
+	uart_port_lock(&priv->port);
 	handled = 0;
 	while (next) {
 		iid = pch_uart_hal_get_iid(priv);
@@ -1073,7 +1070,7 @@ static irqreturn_t pch_uart_interrupt(in
 		handled |= (unsigned int)ret;
 	}
 
-	spin_unlock(&priv->lock);
+	uart_port_unlock(&priv->port);
 	return IRQ_RETVAL(handled);
 }
 
@@ -1184,9 +1181,9 @@ static void pch_uart_break_ctl(struct ua
 	unsigned long flags;
 
 	priv = container_of(port, struct eg20t_port, port);
-	spin_lock_irqsave(&priv->lock, flags);
+	uart_port_lock_irqsave(&priv->port, &flags);
 	pch_uart_hal_set_break(priv, ctl);
-	spin_unlock_irqrestore(&priv->lock, flags);
+	uart_port_unlock_irqrestore(&priv->port, flags);
 }
 
 /* Grab any interrupt resources and initialise any low level driver state. */
@@ -1336,8 +1333,7 @@ static void pch_uart_set_termios(struct
 
 	baud = uart_get_baud_rate(port, termios, old, 0, port->uartclk / 16);
 
-	spin_lock_irqsave(&priv->lock, flags);
-	uart_port_lock(port);
+	uart_port_lock_irqsave(port, &flags);
 
 	uart_update_timeout(port, termios->c_cflag, baud);
 	rtn = pch_uart_hal_set_line(priv, baud, parity, bits, stb);
@@ -1350,8 +1346,7 @@ static void pch_uart_set_termios(struct
 		tty_termios_encode_baud_rate(termios, baud, baud);
 
 out:
-	uart_port_unlock(port);
-	spin_unlock_irqrestore(&priv->lock, flags);
+	uart_port_unlock_irqrestore(port, flags);
 }
 
 static const char *pch_uart_type(struct uart_port *port)
@@ -1555,7 +1550,6 @@ pch_console_write(struct console *co, co
 {
 	struct eg20t_port *priv;
 	unsigned long flags;
-	int priv_locked = 1;
 	int port_locked = 1;
 	u8 ier;
 
@@ -1565,15 +1559,11 @@ pch_console_write(struct console *co, co
 
 	local_irq_save(flags);
 	if (priv->port.sysrq) {
-		/* call to uart_handle_sysrq_char already took the priv lock */
-		priv_locked = 0;
 		/* serial8250_handle_port() already took the port lock */
 		port_locked = 0;
 	} else if (oops_in_progress) {
-		priv_locked = spin_trylock(&priv->lock);
 		port_locked = uart_port_trylock(&priv->port);
 	} else {
-		spin_lock(&priv->lock);
 		uart_port_lock(&priv->port);
 	}
 
@@ -1595,8 +1585,6 @@ pch_console_write(struct console *co, co
 
 	if (port_locked)
 		uart_port_unlock(&priv->port);
-	if (priv_locked)
-		spin_unlock(&priv->lock);
 	local_irq_restore(flags);
 }
 
@@ -1694,8 +1682,6 @@ static struct eg20t_port *pch_uart_init_
 	pci_enable_msi(pdev);
 	pci_set_master(pdev);
 
-	spin_lock_init(&priv->lock);
-
 	iobase = pci_resource_start(pdev, 0);
 	mapbase = pci_resource_start(pdev, 1);
 	priv->mapbase = mapbase;