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tty: serial: imx: keep console clocks always on 

commit e67c139c48 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: 1cf93e0d54 ("serial: imx: remove the uart_console() check")
Acked-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Fugang 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: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
5.4-rM2-2.2.x-imx-squashed
Fugang Duan 2020-11-11 10:51:36 +08:00 committed by Greg Kroah-Hartman
parent 663f70f1f5
commit 772ff2c77c
1 changed files with 3 additions and 17 deletions
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20
drivers/tty/serial/imx.c
View File

@ -1942,16 +1942,6 @@ imx_uart_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;
@ -1987,9 +1977,6 @@ imx_uart_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);
}
/*
@ -2090,15 +2077,14 @@ imx_uart_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;