Commit 2af52148 authored by Sebastian Andrzej Siewior's avatar Sebastian Andrzej Siewior Committed by Greg Kroah-Hartman
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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: default avatarSebastian Andrzej Siewior <bigeasy@linutronix.de>
Link: https://lore.kernel.org/r/20240301215246.891055-11-bigeasy@linutronix.de


Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 6ba52968

drivers/tty/serial/owl-uart.c

+12 −18
Original line number Diff line number Diff line
@@ -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;



	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_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,