[PATCH tty v1 72/74] serial: ucc_uart: Use port lock wrappers

John Ogness john.ogness at linutronix.de
Fri Sep 15 04:38:29 AEST 2023

From: Thomas Gleixner <tglx at linutronix.de>

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

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

Converted with coccinelle. No functional change.

Signed-off-by: Thomas Gleixner <tglx at linutronix.de>
 drivers/tty/serial/ucc_uart.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/tty/serial/ucc_uart.c b/drivers/tty/serial/ucc_uart.c
index b06661b80f41..ed7a6bb5596a 100644
--- a/drivers/tty/serial/ucc_uart.c
+++ b/drivers/tty/serial/ucc_uart.c
@@ -931,7 +931,7 @@ static void qe_uart_set_termios(struct uart_port *port,
 	baud = uart_get_baud_rate(port, termios, old, 0, port->uartclk / 16);
 	/* Do we really need a spinlock here? */
-	spin_lock_irqsave(&port->lock, flags);
+	uart_port_lock_irqsave(port, &flags);
 	/* Update the per-port timeout. */
 	uart_update_timeout(port, termios->c_cflag, baud);
@@ -949,7 +949,7 @@ static void qe_uart_set_termios(struct uart_port *port,
 		qe_setbrg(qe_port->us_info.tx_clock, baud, 16);
-	spin_unlock_irqrestore(&port->lock, flags);
+	uart_port_unlock_irqrestore(port, flags);

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