serial: rda: Use uart_prepare_sysrq_char() to handle sysrq.

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.

Handle sysrq requests sysrq once the port lock is dropped.
Remove the special case in the console write routine an always use the
complete locking function.

Cc: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-unisoc@lists.infradead.org
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Link: https://lore.kernel.org/r/20240301215246.891055-12-bigeasy@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/serial/rda-uart.c b/drivers/tty/serial/rda-uart.c
index 13deb355cf1bc36509a3c8676bb3aa8eaa11f437..82def9b8632a56102470d3f45f170a4750f3541a 100644 (file)
--- a/drivers/tty/serial/rda-uart.c
+++ b/drivers/tty/serial/rda-uart.c
@@ -394,7 +394,8 @@ static void rda_uart_receive_chars(struct uart_port *port)
                val &= 0xff;
 
                port->icount.rx++;
-               tty_insert_flip_char(&port->state->port, val, flag);
+               if (!uart_prepare_sysrq_char(port, val))
+                       tty_insert_flip_char(&port->state->port, val, flag);
 
                status = rda_uart_read(port, RDA_UART_STATUS);
        }
@@ -405,10 +406,9 @@ static void rda_uart_receive_chars(struct uart_port *port)
 static irqreturn_t rda_interrupt(int irq, void *dev_id)
 {
        struct uart_port *port = dev_id;
-       unsigned long flags;
        u32 val, irq_mask;
 
-       uart_port_lock_irqsave(port, &flags);
+       uart_port_lock(port);
 
        /* Clear IRQ cause */
        val = rda_uart_read(port, RDA_UART_IRQ_CAUSE);
@@ -425,7 +425,7 @@ static irqreturn_t rda_interrupt(int irq, void *dev_id)
                rda_uart_send_chars(port);
        }
 
-       uart_port_unlock_irqrestore(port, flags);
+       uart_unlock_and_check_sysrq(port);
 
        return IRQ_HANDLED;
 }
@@ -590,18 +590,12 @@ static void rda_uart_port_write(struct uart_port *port, const char *s,
 {
        u32 old_irq_mask;
        unsigned long flags;
-       int locked;
-
-       local_irq_save(flags);
+       int locked = 1;
 
-       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);
 
        old_irq_mask = rda_uart_read(port, RDA_UART_IRQ_MASK);
        rda_uart_write(port, 0, RDA_UART_IRQ_MASK);
@@ -615,9 +609,7 @@ static void rda_uart_port_write(struct uart_port *port, const char *s,
        rda_uart_write(port, old_irq_mask, RDA_UART_IRQ_MASK);
 
        if (locked)
-               uart_port_unlock(port);
-
-       local_irq_restore(flags);
+               uart_port_unlock_irqrestore(port, flags);
 }
 
 static void rda_uart_console_write(struct console *co, const char *s,