serial: fsl_lpuart: split sysrq handling

Instead of uart_handle_sysrq_char() use uart_prepare_sysrq_char() and
uart_unlock_and_check_sysrq(). This will call handle_sysrq() without
holding the port lock, which in turn let us drop the spin_trylock hack.
Suggested-by: Johan Hovold <johan@kernel.org>
Signed-off-by: Michael Walle <michael@walle.cc>
Link: https://lore.kernel.org/r/20210512141255.18277-5-michael@walle.ccSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/fsl_lpuart.c

@@ -847,7 +847,7 @@ static void lpuart_rxint(struct lpuart_port *sport)
 		sr = readb(sport->port.membase + UARTSR1);
 		rx = readb(sport->port.membase + UARTDR);
 
-		if (uart_handle_sysrq_char(&sport->port, (unsigned char)rx))
+		if (uart_prepare_sysrq_char(&sport->port, rx))
 			continue;
 
 		if (sr & (UARTSR1_PE | UARTSR1_OR | UARTSR1_FE)) {
@@ -893,7 +893,7 @@ static void lpuart_rxint(struct lpuart_port *sport)
 		writeb(UARTSFIFO_RXOF, sport->port.membase + UARTSFIFO);
 	}
 
-	spin_unlock(&sport->port.lock);
+	uart_unlock_and_check_sysrq(&sport->port);
 
 	tty_flip_buffer_push(port);
 }
@@ -924,7 +924,7 @@ static void lpuart32_rxint(struct lpuart_port *sport)
 		rx = lpuart32_read(&sport->port, UARTDATA);
 		rx &= UARTDATA_MASK;
 
-		if (uart_handle_sysrq_char(&sport->port, rx))
+		if (uart_prepare_sysrq_char(&sport->port, rx))
 			continue;
 
 		if (sr & (UARTSTAT_PE | UARTSTAT_OR | UARTSTAT_FE)) {
@@ -959,7 +959,7 @@ static void lpuart32_rxint(struct lpuart_port *sport)
 	}
 
 out:
-	spin_unlock(&sport->port.lock);
+	uart_unlock_and_check_sysrq(&sport->port);
 
 	tty_flip_buffer_push(port);
 }
@@ -2272,7 +2272,7 @@ lpuart_console_write(struct console *co, const char *s, unsigned int count)
 	unsigned long flags;
 	int locked = 1;
 
-	if (sport->port.sysrq || oops_in_progress)
+	if (oops_in_progress)
 		locked = spin_trylock_irqsave(&sport->port.lock, flags);
 	else
 		spin_lock_irqsave(&sport->port.lock, flags);
@@ -2302,7 +2302,7 @@ lpuart32_console_write(struct console *co, const char *s, unsigned int count)
 	unsigned long flags;
 	int locked = 1;
 
-	if (sport->port.sysrq || oops_in_progress)
+	if (oops_in_progress)
 		locked = spin_trylock_irqsave(&sport->port.lock, flags);
 	else
 		spin_lock_irqsave(&sport->port.lock, flags);