serial: stm32: defer sysrq processing

Use the uart_unlock_and_check_sysrq() helper to defer sysrq processing
until receive processing is done and the port lock has been released.

This allows cleaning up the console_write() implementation by not having
to work around the recursive sysrq case (by dropping locking completely)
and also makes the console code work with PREEMPT_RT by no longer
relying on local_irq_save().

Reviewed-by: Valentin Caron<valentin.caron@foss.st.com>
Signed-off-by: Johan Hovold <johan@kernel.org>
Link: https://lore.kernel.org/r/20210416140557.25177-4-johan@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/serial/stm32-usart.c b/drivers/tty/serial/stm32-usart.c
index 3524ed2..24a1dfe 100644 (file)
--- a/drivers/tty/serial/stm32-usart.c
+++ b/drivers/tty/serial/stm32-usart.c
@@ -270,12 +270,12 @@ static void stm32_usart_receive_chars(struct uart_port *port, bool threaded)
                        }
                }
 
-               if (uart_handle_sysrq_char(port, c))
+               if (uart_prepare_sysrq_char(port, c))
                        continue;
                uart_insert_char(port, sr, USART_SR_ORE, c, flag);
        }
 
-       spin_unlock(&port->lock);
+       uart_unlock_and_check_sysrq(port);
 
        tty_flip_buffer_push(tport);
 }
@@ -1430,13 +1430,10 @@ static void stm32_usart_console_write(struct console *co, const char *s,
        u32 old_cr1, new_cr1;
        int locked = 1;
 
-       local_irq_save(flags);
-       if (port->sysrq)
-               locked = 0;
-       else if (oops_in_progress)
-               locked = spin_trylock(&port->lock);
+       if (oops_in_progress)
+               locked = spin_trylock_irqsave(&port->lock, flags);
        else
-               spin_lock(&port->lock);
+               spin_lock_irqsave(&port->lock, flags);
 
        /* Save and disable interrupts, enable the transmitter */
        old_cr1 = readl_relaxed(port->membase + ofs->cr1);
@@ -1450,8 +1447,7 @@ static void stm32_usart_console_write(struct console *co, const char *s,
        writel_relaxed(old_cr1, port->membase + ofs->cr1);
 
        if (locked)
-               spin_unlock(&port->lock);
-       local_irq_restore(flags);
+               spin_unlock_irqrestore(&port->lock, flags);
 }
 
 static int stm32_usart_console_setup(struct console *co, char *options)