[PATCH 5.9 199/252] tty: serial: imx: keep console clocks always on

Greg Kroah-Hartman
2020-11-23T13:06:43Z

From: Fugang Duan <fugang.duan@nxp.com>

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: 1cf93e0d5488 ("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>

---
drivers/tty/serial/imx.c | 20 +++-----------------
1 file changed, 3 insertions(+), 17 deletions(-)

--- a/drivers/tty/serial/imx.c
+++ b/drivers/tty/serial/imx.c
@@ -2007,16 +2007,6 @@ imx_uart_console_write(struct console *c
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;
@@ -2052,9 +2042,6 @@ imx_uart_console_write(struct console *c

if (locked)
spin_unlock_irqrestore(&sport->port.lock, flags);
-
- clk_disable(sport->clk_ipg);
- clk_disable(sport->clk_per);
}

/*
@@ -2155,15 +2142,14 @@ imx_uart_console_setup(struct console *c

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;