Commit 4e5788c0 authored by Sebastian Andrzej Siewior's avatar Sebastian Andrzej Siewior Committed by Greg Kroah-Hartman
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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: default avatarSebastian Andrzej Siewior <bigeasy@linutronix.de>
Link: https://lore.kernel.org/r/20240301215246.891055-6-bigeasy@linutronix.de


Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent fb793b95

drivers/tty/serial/msm_serial.c

+10 −23
Original line number Diff line number Diff line
@@ -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,