serial: meson: Use uart_prepare_sysrq_char().

The port lock is a spinlock_t which is becomes a sleeping lock on PREEMPT_RT.
The driver splits the locking function into two parts: local_irq_save() and
uart_port_lock() and this breaks PREEMPT_RT.

Delay handling sysrq until port lock is dropped.
Remove the special case in the console write routine an always use the
complete locking function.

Cc: Kevin Hilman <khilman@baylibre.com>
Cc: Jerome Brunet <jbrunet@baylibre.com>
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-amlogic@lists.infradead.org
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Link: https://lore.kernel.org/r/20240301215246.891055-5-bigeasy@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/serial/meson_uart.c b/drivers/tty/serial/meson_uart.c
index 8395688f5ee926f92a2345ab1735c2b9058d7a06..6feac459c0cf4f7a2b6fff658023205d9fa81d78 100644 (file)
--- a/drivers/tty/serial/meson_uart.c
+++ b/drivers/tty/serial/meson_uart.c
@@ -220,7 +220,7 @@ static void meson_receive_chars(struct uart_port *port)
                                continue;
                }
 
-               if (uart_handle_sysrq_char(port, ch))
+               if (uart_prepare_sysrq_char(port, ch))
                        continue;
 
                if ((status & port->ignore_status_mask) == 0)
@@ -248,7 +248,7 @@ static irqreturn_t meson_uart_interrupt(int irq, void *dev_id)
                        meson_uart_start_tx(port);
        }
 
-       uart_port_unlock(port);
+       uart_unlock_and_check_sysrq(port);
 
        return IRQ_HANDLED;
 }
@@ -556,18 +556,13 @@ static void meson_serial_port_write(struct uart_port *port, const char *s,
                                    u_int count)
 {
        unsigned long flags;
-       int locked;
+       int locked = 1;
        u32 val, tmp;
 
-       local_irq_save(flags);
-       if (port->sysrq) {
-               locked = 0;
-       } else if (oops_in_progress) {
-               locked = uart_port_trylock(port);
-       } else {
-               uart_port_lock(port);
-               locked = 1;
-       }
+       if (oops_in_progress)
+               locked = uart_port_trylock_irqsave(port, &flags);
+       else
+               uart_port_lock_irqsave(port, &flags);
 
        val = readl(port->membase + AML_UART_CONTROL);
        tmp = val & ~(AML_UART_TX_INT_EN | AML_UART_RX_INT_EN);
@@ -577,8 +572,7 @@ static void meson_serial_port_write(struct uart_port *port, const char *s,
        writel(val, port->membase + AML_UART_CONTROL);
 
        if (locked)
-               uart_port_unlock(port);
-       local_irq_restore(flags);
+               uart_port_unlock_irqrestore(port, flags);
 }
 
 static void meson_serial_console_write(struct console *co, const char *s,