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Commit 5f34104d authored by Fugang Duan's avatar Fugang Duan Committed by Greg Kroah-Hartman
Browse files

tty: serial: imx: keep console clocks always on 



commit e67c139c488e84e7eae6c333231e791f0e89b3fb upstream.

For below code, there has chance to cause deadlock in SMP system:
Thread 1:
clk_enable_lock();
pr_info("debug message");
clk_enable_unlock();

Thread 2:
imx_uart_console_write()
	clk_enable()
		clk_enable_lock();

Thread 1:
Acuired clk enable_lock -> printk -> console_trylock_spinning
Thread 2:
console_unlock() -> imx_uart_console_write -> clk_disable -> Acquite clk enable_lock

So the patch is to keep console port clocks always on like
other console drivers.

Fixes: 1cf93e0d ("serial: imx: remove the uart_console() check")
Acked-by: default avatarUwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: default avatarFugang Duan <fugang.duan@nxp.com>
Link: https://lore.kernel.org/r/20201111025136.29818-1-fugang.duan@nxp.com


Cc: stable <stable@vger.kernel.org>
[fix up build warning - gregkh]
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 919c5184

drivers/tty/serial/imx.c

+3 −17
Original line number Diff line number Diff line
@@ -1787,16 +1787,6 @@ imx_console_write(struct console *co, const char *s, unsigned int count) 
	unsigned int ucr1;

	unsigned long flags = 0;

	int locked = 1;

	int retval;



	retval = clk_enable(sport->clk_per);

	if (retval)

		return;

	retval = clk_enable(sport->clk_ipg);

	if (retval) {

		clk_disable(sport->clk_per);

		return;

	}



	if (sport->port.sysrq)

		locked = 0;
@@ -1832,9 +1822,6 @@ imx_console_write(struct console *co, const char *s, unsigned int count) 


	if (locked)

		spin_unlock_irqrestore(&sport->port.lock, flags);



	clk_disable(sport->clk_ipg);

	clk_disable(sport->clk_per);

}



/*
@@ -1935,15 +1922,14 @@ imx_console_setup(struct console *co, char *options) 


	retval = uart_set_options(&sport->port, co, baud, parity, bits, flow);



	clk_disable(sport->clk_ipg);

	if (retval) {

		clk_unprepare(sport->clk_ipg);

		clk_disable_unprepare(sport->clk_ipg);

		goto error_console;

	}



	retval = clk_prepare(sport->clk_per);

	retval = clk_prepare_enable(sport->clk_per);

	if (retval)

		clk_unprepare(sport->clk_ipg);

		clk_disable_unprepare(sport->clk_ipg);



error_console:

	return retval;