serial: msm: 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: Bjorn Andersson <andersson@kernel.org>
Cc: Konrad Dybcio <konrad.dybcio@linaro.org>
Cc: linux-arm-msm@vger.kernel.org
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Link: https://lore.kernel.org/r/20240301215246.891055-6-bigeasy@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/serial/msm_serial.c b/drivers/tty/serial/msm_serial.c
index e24204a..d27c4c8 100644 (file)
--- a/drivers/tty/serial/msm_serial.c
+++ b/drivers/tty/serial/msm_serial.c
@@ -588,16 +588,14 @@ static void msm_complete_rx_dma(void *args)
                if (!(port->read_status_mask & MSM_UART_SR_RX_BREAK))
                        flag = TTY_NORMAL;
 
-               uart_port_unlock_irqrestore(port, flags);
-               sysrq = uart_handle_sysrq_char(port, dma->virt[i]);
-               uart_port_lock_irqsave(port, &flags);
+               sysrq = uart_prepare_sysrq_char(port, dma->virt[i]);
                if (!sysrq)
                        tty_insert_flip_char(tport, dma->virt[i], flag);
        }
 
        msm_start_rx_dma(msm_port);
 done:
-       uart_port_unlock_irqrestore(port, flags);
+       uart_unlock_and_check_sysrq_irqrestore(port, flags);
 
        if (count)
                tty_flip_buffer_push(tport);
@@ -763,9 +761,7 @@ static void msm_handle_rx_dm(struct uart_port *port, unsigned int misr)
                        if (!(port->read_status_mask & MSM_UART_SR_RX_BREAK))
                                flag = TTY_NORMAL;
 
-                       uart_port_unlock(port);
-                       sysrq = uart_handle_sysrq_char(port, buf[i]);
-                       uart_port_lock(port);
+                       sysrq = uart_prepare_sysrq_char(port, buf[i]);
                        if (!sysrq)
                                tty_insert_flip_char(tport, buf[i], flag);
                }
@@ -825,9 +821,7 @@ static void msm_handle_rx(struct uart_port *port)
                else if (sr & MSM_UART_SR_PAR_FRAME_ERR)
                        flag = TTY_FRAME;
 
-               uart_port_unlock(port);
-               sysrq = uart_handle_sysrq_char(port, c);
-               uart_port_lock(port);
+               sysrq = uart_prepare_sysrq_char(port, c);
                if (!sysrq)
                        tty_insert_flip_char(tport, c, flag);
        }
@@ -948,11 +942,10 @@ static irqreturn_t msm_uart_irq(int irq, void *dev_id)
        struct uart_port *port = dev_id;
        struct msm_port *msm_port = to_msm_port(port);
        struct msm_dma *dma = &msm_port->rx_dma;
-       unsigned long flags;
        unsigned int misr;
        u32 val;
 
-       uart_port_lock_irqsave(port, &flags);
+       uart_port_lock(port);
        misr = msm_read(port, MSM_UART_MISR);
        msm_write(port, 0, MSM_UART_IMR); /* disable interrupt */
 
@@ -984,7 +977,7 @@ static irqreturn_t msm_uart_irq(int irq, void *dev_id)
                msm_handle_delta_cts(port);
 
        msm_write(port, msm_port->imr, MSM_UART_IMR); /* restore interrupt */
-       uart_port_unlock_irqrestore(port, flags);
+       uart_unlock_and_check_sysrq(port);
 
        return IRQ_HANDLED;
 }
@@ -1621,14 +1614,10 @@ static void __msm_console_write(struct uart_port *port, const char *s,
                        num_newlines++;
        count += num_newlines;
 
-       local_irq_save(flags);
-
-       if (port->sysrq)
-               locked = 0;
-       else if (oops_in_progress)
-               locked = uart_port_trylock(port);
+       if (oops_in_progress)
+               locked = uart_port_trylock_irqsave(port, &flags);
        else
-               uart_port_lock(port);
+               uart_port_lock_irqsave(port, &flags);
 
        if (is_uartdm)
                msm_reset_dm_count(port, count);
@@ -1667,9 +1656,7 @@ static void __msm_console_write(struct uart_port *port, const char *s,
        }
 
        if (locked)
-               uart_port_unlock(port);
-
-       local_irq_restore(flags);
+               uart_port_unlock_irqrestore(port, flags);
 }
 
 static void msm_console_write(struct console *co, const char *s,