[PATCH] serial: imx: Fix serial clock unbalance

[Shawn Guo]

On Sun, Jun 09, 2013 at 03:17:18PM -0300, Fabio Estevam wrote:
> From: Fabio Estevam <fabio.estevam at freescale.com>
> 
> Since commit 0c375501 (serial: imx: enable the clocks for console), the 
> imx_startup() function calls clk_prepare_enable conditionally, so we need to 
> call clk_disable_unprepare inside imx_shutdown() under the same condition to
> avoid unbalanced clock calls.
> 
> This avoids the following warning:
> 
> ------------[ cut here ]------------
> WARNING: CPU: 0 PID: 70 at drivers/clk/clk.c:780 __clk_disable+0x68/0x84()
> Modules linked in:
> CPU: 0 PID: 70 Comm: mountall Not tainted 3.10.0-rc4-next-20130607+ #435
> Backtrace: 
> [<800116a4>] (dump_backtrace+0x0/0x10c) from [<80011844>] (show_stack+0x18/0x1c)
>  r6:8069f4e8 r5:0000030c r4:00000000 r3:00000000
> [<8001182c>] (show_stack+0x0/0x1c) from [<8053bce0>] (dump_stack+0x78/0x94)
> [<8053bc68>] (dump_stack+0x0/0x94) from [<80023df8>] (warn_slowpath_common+0x6c/0x8c)
>  r4:00000000 r3:00000000
> [<80023d8c>] (warn_slowpath_common+0x0/0x8c) from [<80023e3c>] (warn_slowpath_null+0x24/0x2c)
>  r8:bf2ed008 r7:bfaa9810 r6:000f0013 r5:bf824b80 r4:bf824b80
> [<80023e18>] (warn_slowpath_null+0x0/0x2c) from [<8041af84>] (__clk_disable+0x68/0x84)
> [<8041af1c>] (__clk_disable+0x0/0x84) from [<8041b098>] (clk_disable+0x20/0x2c)
>  r4:600f0013 r3:00000001
> [<8041b078>] (clk_disable+0x0/0x2c) from [<802c93e8>] (imx_shutdown+0xbc/0xec)
>  r5:bf824b80 r4:bfaa9810
> [<802c932c>] (imx_shutdown+0x0/0xec) from [<802c63a0>] (uart_port_shutdown+0x34/0x40)
>  r5:bf86f860 r4:bfaa9810
> [<802c636c>] (uart_port_shutdown+0x0/0x40) from [<802c68c0>] (uart_shutdown+0x98/0xc4)
>  r4:bf86f800 r3:00000000
> [<802c6828>] (uart_shutdown+0x0/0xc4) from [<802c7514>] (uart_close+0x5c/0x198)
>  r7:bfaa9810 r6:bf274400 r5:bf86f86c r4:bf86f800
> [<802c74b8>] (uart_close+0x0/0x198) from [<802ac648>] (tty_release+0xf8/0x500)
> [<802ac550>] (tty_release+0x0/0x500) from [<800c5a30>] (__fput+0x9c/0x208)
> [<800c5994>] (__fput+0x0/0x208) from [<800c5bac>] (____fput+0x10/0x14)
> [<800c5b9c>] (____fput+0x0/0x14) from [<80040234>] (task_work_run+0xb4/0xec)
> [<80040180>] (task_work_run+0x0/0xec) from [<80029238>] (do_exit+0x2b0/0x920)
>  r8:8000e144 r7:000000f8 r6:bf306300 r5:00000000 r4:bfac1180
> [<80028f88>] (do_exit+0x0/0x920) from [<80029a4c>] (do_group_exit+0x50/0xd4)
>  r7:000000f8
> [<800299fc>] (do_group_exit+0x0/0xd4) from [<80029ae8>] (__wake_up_parent+0x0/0x28)
>  r7:000000f8 r6:00000001 r5:0006f7ae r4:0006f79a
> [<80029ad0>] (SyS_exit_group+0x0/0x18) from [<8000dfc0>] (ret_fast_syscall+0x0/0x30)
> ---[ end trace 16d080eb7efea4e9 ]---
> 
> Reported-by: Shawn Guo <shawn.guo at linaro.org>
> Signed-off-by: Fabio Estevam <fabio.estevam at freescale.com>

Tested-by: Shawn Guo <shawn.guo at linaro.org>