Commit 32c694ec authored by Sebastian Andrzej Siewior's avatar Sebastian Andrzej Siewior Committed by Greg Kroah-Hartman
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serial: sifive: 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: Palmer Dabbelt <palmer@dabbelt.com>
Cc: Paul Walmsley <paul.walmsley@sifive.com>
Cc: linux-riscv@lists.infradead.org
Signed-off-by: default avatarSebastian Andrzej Siewior <bigeasy@linutronix.de>
Link: https://lore.kernel.org/r/20240301215246.891055-13-bigeasy@linutronix.de


Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent bb0b3142

drivers/tty/serial/sifive.c

+7 −10
Original line number Diff line number Diff line
@@ -412,6 +412,7 @@ static void __ssp_receive_chars(struct sifive_serial_port *ssp) 
			break;



		ssp->port.icount.rx++;

		if (!uart_prepare_sysrq_char(&ssp->port, ch))

			uart_insert_char(&ssp->port, 0, 0, ch, TTY_NORMAL);

	}
@@ -534,7 +535,7 @@ static irqreturn_t sifive_serial_irq(int irq, void *dev_id) 
	if (ip & SIFIVE_SERIAL_IP_TXWM_MASK)

		__ssp_transmit_chars(ssp);



	uart_port_unlock(&ssp->port);

	uart_unlock_and_check_sysrq(&ssp->port);



	return IRQ_HANDLED;

}
@@ -791,13 +792,10 @@ static void sifive_serial_console_write(struct console *co, const char *s, 
	if (!ssp)

		return;



	local_irq_save(flags);

	if (ssp->port.sysrq)

		locked = 0;

	else if (oops_in_progress)

		locked = uart_port_trylock(&ssp->port);

	if (oops_in_progress)

		locked = uart_port_trylock_irqsave(&ssp->port, &flags);

	else

		uart_port_lock(&ssp->port);

		uart_port_lock_irqsave(&ssp->port, &flags);



	ier = __ssp_readl(ssp, SIFIVE_SERIAL_IE_OFFS);

	__ssp_writel(0, SIFIVE_SERIAL_IE_OFFS, ssp);
@@ -807,8 +805,7 @@ static void sifive_serial_console_write(struct console *co, const char *s, 
	__ssp_writel(ier, SIFIVE_SERIAL_IE_OFFS, ssp);



	if (locked)

		uart_port_unlock(&ssp->port);

	local_irq_restore(flags);

		uart_port_unlock_irqrestore(&ssp->port, flags);

}



static int sifive_serial_console_setup(struct console *co, char *options)