Commit 2432f71c authored by Sebastian Andrzej Siewior's avatar Sebastian Andrzej Siewior Committed by Greg Kroah-Hartman
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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: default avatarSebastian Andrzej Siewior <bigeasy@linutronix.de>
Link: https://lore.kernel.org/r/20240301215246.891055-2-bigeasy@linutronix.de


Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 65295eba

drivers/tty/serial/amba-pl011.c

+8 −16
Original line number Diff line number Diff line
@@ -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);

}