serial: owl: 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: Andreas Färber <afaerber@suse.de>
Cc: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-actions@lists.infradead.org
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Link: https://lore.kernel.org/r/20240301215246.891055-11-bigeasy@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/serial/owl-uart.c b/drivers/tty/serial/owl-uart.c
index d9fe85397741dd7813571133ad85d928566f0783..8b60ac0ad7cd341f0415fab558f3d5d2892d68e5 100644 (file)
--- a/drivers/tty/serial/owl-uart.c
+++ b/drivers/tty/serial/owl-uart.c
@@ -199,6 +199,7 @@ static void owl_uart_receive_chars(struct uart_port *port)
        stat = owl_uart_read(port, OWL_UART_STAT);
        while (!(stat & OWL_UART_STAT_RFEM)) {
                char flag = TTY_NORMAL;
+               bool sysrq;
 
                if (stat & OWL_UART_STAT_RXER)
                        port->icount.overrun++;
@@ -217,7 +218,9 @@ static void owl_uart_receive_chars(struct uart_port *port)
                val = owl_uart_read(port, OWL_UART_RXDAT);
                val &= 0xff;
 
-               if ((stat & port->ignore_status_mask) == 0)
+               sysrq = uart_prepare_sysrq_char(port, val);
+
+               if (!sysrq && (stat & port->ignore_status_mask) == 0)
                        tty_insert_flip_char(&port->state->port, val, flag);
 
                stat = owl_uart_read(port, OWL_UART_STAT);
@@ -229,10 +232,9 @@ static void owl_uart_receive_chars(struct uart_port *port)
 static irqreturn_t owl_uart_irq(int irq, void *dev_id)
 {
        struct uart_port *port = dev_id;
-       unsigned long flags;
        u32 stat;
 
-       uart_port_lock_irqsave(port, &flags);
+       uart_port_lock(port);
 
        stat = owl_uart_read(port, OWL_UART_STAT);
 
@@ -246,7 +248,7 @@ static irqreturn_t owl_uart_irq(int irq, void *dev_id)
        stat |= OWL_UART_STAT_RIP | OWL_UART_STAT_TIP;
        owl_uart_write(port, stat, OWL_UART_STAT);
 
-       uart_port_unlock_irqrestore(port, flags);
+       uart_unlock_and_check_sysrq(port);
 
        return IRQ_HANDLED;
 }
@@ -508,18 +510,12 @@ static void owl_uart_port_write(struct uart_port *port, const char *s,
 {
        u32 old_ctl, val;
        unsigned long flags;
-       int locked;
+       int locked = 1;
 
-       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);
 
        old_ctl = owl_uart_read(port, OWL_UART_CTL);
        val = old_ctl | OWL_UART_CTL_TRFS_TX;
@@ -541,9 +537,7 @@ static void owl_uart_port_write(struct uart_port *port, const char *s,
        owl_uart_write(port, old_ctl, OWL_UART_CTL);
 
        if (locked)
-               uart_port_unlock(port);
-
-       local_irq_restore(flags);
+               uart_port_unlock_irqrestore(port, flags);
 }
 
 static void owl_uart_console_write(struct console *co, const char *s,