serial: arc_uart: Use port lock wrappers

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/20230914183831.587273-21-john.ogness@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/serial/arc_uart.c b/drivers/tty/serial/arc_uart.c
index ad4ae19..1aa5b2b 100644 (file)
--- a/drivers/tty/serial/arc_uart.c
+++ b/drivers/tty/serial/arc_uart.c
@@ -279,9 +279,9 @@ static irqreturn_t arc_serial_isr(int irq, void *dev_id)
        if (status & RXIENB) {
 
                /* already in ISR, no need of xx_irqsave */
-               spin_lock(&port->lock);
+               uart_port_lock(port);
                arc_serial_rx_chars(port, status);
-               spin_unlock(&port->lock);
+               uart_port_unlock(port);
        }
 
        if ((status & TXIENB) && (status & TXEMPTY)) {
@@ -291,12 +291,12 @@ static irqreturn_t arc_serial_isr(int irq, void *dev_id)
                 */
                UART_TX_IRQ_DISABLE(port);
 
-               spin_lock(&port->lock);
+               uart_port_lock(port);
 
                if (!uart_tx_stopped(port))
                        arc_serial_tx_chars(port);
 
-               spin_unlock(&port->lock);
+               uart_port_unlock(port);
        }
 
        return IRQ_HANDLED;
@@ -366,7 +366,7 @@ arc_serial_set_termios(struct uart_port *port, struct ktermios *new,
        uartl = hw_val & 0xFF;
        uarth = (hw_val >> 8) & 0xFF;
 
-       spin_lock_irqsave(&port->lock, flags);
+       uart_port_lock_irqsave(port, &flags);
 
        UART_ALL_IRQ_DISABLE(port);
 
@@ -391,7 +391,7 @@ arc_serial_set_termios(struct uart_port *port, struct ktermios *new,
 
        uart_update_timeout(port, new->c_cflag, baud);
 
-       spin_unlock_irqrestore(&port->lock, flags);
+       uart_port_unlock_irqrestore(port, flags);
 }
 
 static const char *arc_serial_type(struct uart_port *port)
@@ -521,9 +521,9 @@ static void arc_serial_console_write(struct console *co, const char *s,
        struct uart_port *port = &arc_uart_ports[co->index].port;
        unsigned long flags;
 
-       spin_lock_irqsave(&port->lock, flags);
+       uart_port_lock_irqsave(port, &flags);
        uart_console_write(port, s, count, arc_serial_console_putchar);
-       spin_unlock_irqrestore(&port->lock, flags);
+       uart_port_unlock_irqrestore(port, flags);
 }
 
 static struct console arc_console = {