serial: amba-pl011: 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: Russell King <linux@armlinux.org.uk>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Link: https://lore.kernel.org/r/20240301215246.891055-2-bigeasy@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/serial/amba-pl011.c b/drivers/tty/serial/amba-pl011.c
index cf2c890a560f05204e249b931668deca04b3cb27..2fa3fb30dc6c7552667ea68691b28115569c303e 100644 (file)
--- a/drivers/tty/serial/amba-pl011.c
+++ b/drivers/tty/serial/amba-pl011.c
@@ -348,10 +348,7 @@ static int pl011_fifo_to_tty(struct uart_amba_port *uap)
                                flag = TTY_FRAME;
                }
 
-               uart_port_unlock(&uap->port);
-               sysrq = uart_handle_sysrq_char(&uap->port, ch & 255);
-               uart_port_lock(&uap->port);
-
+               sysrq = uart_prepare_sysrq_char(&uap->port, ch & 255);
                if (!sysrq)
                        uart_insert_char(&uap->port, ch, UART011_DR_OE, ch, flag);
        }
@@ -1017,7 +1014,7 @@ static void pl011_dma_rx_callback(void *data)
        ret = pl011_dma_rx_trigger_dma(uap);
 
        pl011_dma_rx_chars(uap, pending, lastbuf, false);
-       uart_port_unlock_irq(&uap->port);
+       uart_unlock_and_check_sysrq(&uap->port);
        /*
         * Do this check after we picked the DMA chars so we don't
         * get some IRQ immediately from RX.
@@ -1540,11 +1537,10 @@ static void check_apply_cts_event_workaround(struct uart_amba_port *uap)
 static irqreturn_t pl011_int(int irq, void *dev_id)
 {
        struct uart_amba_port *uap = dev_id;
-       unsigned long flags;
        unsigned int status, pass_counter = AMBA_ISR_PASS_LIMIT;
        int handled = 0;
 
-       uart_port_lock_irqsave(&uap->port, &flags);
+       uart_port_lock(&uap->port);
        status = pl011_read(uap, REG_RIS) & uap->im;
        if (status) {
                do {
@@ -1573,7 +1569,7 @@ static irqreturn_t pl011_int(int irq, void *dev_id)
                handled = 1;
        }
 
-       uart_port_unlock_irqrestore(&uap->port, flags);
+       uart_unlock_and_check_sysrq(&uap->port);
 
        return IRQ_RETVAL(handled);
 }
@@ -2322,13 +2318,10 @@ pl011_console_write(struct console *co, const char *s, unsigned int count)
 
        clk_enable(uap->clk);
 
-       local_irq_save(flags);
-       if (uap->port.sysrq)
-               locked = 0;
-       else if (oops_in_progress)
-               locked = uart_port_trylock(&uap->port);
+       if (oops_in_progress)
+               locked = uart_port_trylock_irqsave(&uap->port, &flags);
        else
-               uart_port_lock(&uap->port);
+               uart_port_lock_irqsave(&uap->port, &flags);
 
        /*
         *      First save the CR then disable the interrupts
@@ -2354,8 +2347,7 @@ pl011_console_write(struct console *co, const char *s, unsigned int count)
                pl011_write(old_cr, uap, REG_CR);
 
        if (locked)
-               uart_port_unlock(&uap->port);
-       local_irq_restore(flags);
+               uart_port_unlock_irqrestore(&uap->port, flags);
 
        clk_disable(uap->clk);
 }