Commit 0c727a42 authored Aug 18, 2015 by Fabio Estevam Committed by Greg Kroah-Hartman Oct 04, 2015

Revert "serial: imx: remove unbalanced clk_prepare"



This reverts commit 9e7b399d.

Commit ("9e7b399d") causes the following warning and sometimes
also hangs the system:

------------[ cut here ]------------
 WARNING: CPU: 0 PID: 0 at kernel/locking/mutex.c:868 mutex_trylock+0x20c/0x22c()
 DEBUG_LOCKS_WARN_ON(in_interrupt())
 Modules linked in:
CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.2.0-rc7-next-20150818-00001-g14418a6 #4
Hardware name: Freescale i.MX6 Quad/DualLite (Device Tree)
Backtrace:
[<80012f08>] (dump_backtrace) from [<800130a4>] (show_stack+0x18/0x1c)
r6:00000364 r5:00000000 r4:00000000 r3:00000000
[<8001308c>] (show_stack) from [<807902b8>] (dump_stack+0x88/0xa4)
[<80790230>] (dump_stack) from [<8002a604>] (warn_slowpath_common+0x80/0xbc)
r5:807945c4 r4:80ab3b50
[<8002a584>] (warn_slowpath_common) from [<8002a6e4>] (warn_slowpath_fmt+0x38/0x40)
r8:00000000 r7:8131100c r6:8054c3cc r5:8131300c r4:80b0a570
[<8002a6b0>] (warn_slowpath_fmt) from [<807945c4>] (mutex_trylock+0x20c/0x22c)
r3:8095d0d8 r2:8095ab28
[<807943b8>] (mutex_trylock) from [<8054c3cc>] (clk_prepare_lock+0x14/0xf4)
r7:8131100c r6:be3f0c80 r5:00000037 r4:be3f0c80
[<8054c3b8>] (clk_prepare_lock) from [<8054dbfc>] (clk_prepare+0x18/0x30)
r5:00000037 r4:be3f0c80
[<8054dbe4>] (clk_prepare) from [<8036a600>] (imx_console_write+0x30/0x244)
r4:812d0bc8 r3:8132b9a4

To reproduce the problem we only need to let the board idle for something
like 30 seconds.

Tested on a imx6q-sabresd.

Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>
Reviewed-by: Eduardo Valentin <edubezval@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

parent 9ffecb10

drivers/tty/serial/imx.c

+14 −6

Original line number	Original line	Diff line number	Diff line
	@@ -1631,12 +1631,12 @@ imx_console_write(struct console co, const char s, unsigned int count)
	int locked = 1;		int locked = 1;
	int retval;		int retval;

	retval = clk_prepare_enable(sport->clk_per);		retval = clk_enable(sport->clk_per);
	if (retval)		if (retval)
	return;		return;
	retval = clk_prepare_enable(sport->clk_ipg);		retval = clk_enable(sport->clk_ipg);
	if (retval) {		if (retval) {
	clk_disable_unprepare(sport->clk_per);		clk_disable(sport->clk_per);
	return;		return;
	}		}

	@@ -1675,8 +1675,8 @@ imx_console_write(struct console co, const char s, unsigned int count)
	if (locked)		if (locked)
	spin_unlock_irqrestore(&sport->port.lock, flags);		spin_unlock_irqrestore(&sport->port.lock, flags);

	clk_disable_unprepare(sport->clk_ipg);		clk_disable(sport->clk_ipg);
	clk_disable_unprepare(sport->clk_per);		clk_disable(sport->clk_per);
	}		}

	/*		/*
	@@ -1777,6 +1777,14 @@ imx_console_setup(struct console co, char options)

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

			clk_disable(sport->clk_ipg);
			if (retval) {
			clk_unprepare(sport->clk_ipg);
			goto error_console;
			}

			retval = clk_prepare(sport->clk_per);
			if (retval)
	clk_disable_unprepare(sport->clk_ipg);		clk_disable_unprepare(sport->clk_ipg);

	error_console:		error_console: