linux-kernel - [014/262] serial-core: power up uart port early before we do set

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Date:	Wed, 09 Nov 2011 13:25:36 -0800
From:	Greg KH <gregkh@...e.de>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	torvalds@...ux-foundation.org, akpm@...ux-foundation.org,
	alan@...rguk.ukuu.org.uk, Ning Jiang <ning.jiang@...vell.com>
Subject: [014/262] serial-core: power up uart port early before we do set_termios when resuming

3.0-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Ning Jiang <ning.jiang@...vell.com>

commit 94abc56f4d90f289ea32a0a11d3577fcd8cb28fb upstream.

The following patch removed uart_change_pm() in uart_resume_port():

commit 5933a161abcb8d83a2c145177f48027c3c0a8995
Author: Yin Kangkai <kangkai.yin@...ux.intel.com>
    serial-core: reset the console speed on resume

It will break the pxa serial driver when the system resumes from suspend mode
as it will try to set baud rate divider register in set_termios but with
clock off. The register value can not be set correctly on some platform if
the clock is disabled. The pxa driver will check the value and report the
following warning:

------------[ cut here ]------------
WARNING: at drivers/tty/serial/pxa.c:545 serial_pxa_set_termios+0x1dc/0x250()
Modules linked in:
[<c0281f30>] (unwind_backtrace+0x0/0xf0) from [<c029341c>] (warn_slowpath_common+0x4c/0x64)
[<c029341c>] (warn_slowpath_common+0x4c/0x64) from [<c029344c>] (warn_slowpath_null+0x18/0x1c)
[<c029344c>] (warn_slowpath_null+0x18/0x1c) from [<c044b1e4>] (serial_pxa_set_termios+0x1dc/0x250)
[<c044b1e4>] (serial_pxa_set_termios+0x1dc/0x250) from [<c044a840>] (uart_resume_port+0x128/0x2dc)
[<c044a840>] (uart_resume_port+0x128/0x2dc) from [<c044bbe0>] (serial_pxa_resume+0x18/0x24)
[<c044bbe0>] (serial_pxa_resume+0x18/0x24) from [<c0454d34>] (platform_pm_resume+0x40/0x4c)
[<c0454d34>] (platform_pm_resume+0x40/0x4c) from [<c0457ebc>] (pm_op+0x68/0xb4)
[<c0457ebc>] (pm_op+0x68/0xb4) from [<c0458368>] (device_resume+0xb0/0xec)
[<c0458368>] (device_resume+0xb0/0xec) from [<c04584c8>] (dpm_resume+0xe0/0x194)
[<c04584c8>] (dpm_resume+0xe0/0x194) from [<c0458588>] (dpm_resume_end+0xc/0x18)
[<c0458588>] (dpm_resume_end+0xc/0x18) from [<c02c518c>] (suspend_devices_and_enter+0x16c/0x1ac)
[<c02c518c>] (suspend_devices_and_enter+0x16c/0x1ac) from [<c02c5278>] (enter_state+0xac/0xdc)
[<c02c5278>] (enter_state+0xac/0xdc) from [<c02c48ec>] (state_store+0xa0/0xbc)
[<c02c48ec>] (state_store+0xa0/0xbc) from [<c0408f7c>] (kobj_attr_store+0x18/0x1c)
[<c0408f7c>] (kobj_attr_store+0x18/0x1c) from [<c034a6a4>] (sysfs_write_file+0x108/0x140)
[<c034a6a4>] (sysfs_write_file+0x108/0x140) from [<c02fb798>] (vfs_write+0xac/0x134)
[<c02fb798>] (vfs_write+0xac/0x134) from [<c02fb8cc>] (sys_write+0x3c/0x68)
[<c02fb8cc>] (sys_write+0x3c/0x68) from [<c027c700>] (ret_fast_syscall+0x0/0x2c)
---[ end trace 88289eceb4675b04 ]---

This patch fix the problem by adding the power on opertion back for uart
console when console_suspend_enabled is true.

Signed-off-by: Ning Jiang <ning.jiang@...vell.com>
Tested-by: Mayank Rana <mrana@...eaurora.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>

---
 drivers/tty/serial/serial_core.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/drivers/tty/serial/serial_core.c
+++ b/drivers/tty/serial/serial_core.c
@@ -2003,6 +2003,8 @@ int uart_resume_port(struct uart_driver
 		if (port->tty && port->tty->termios && termios.c_cflag == 0)
 			termios = *(port->tty->termios);
 
+		if (console_suspend_enabled)
+			uart_change_pm(state, 0);
 		uport->ops->set_termios(uport, &termios, NULL);
 		if (console_suspend_enabled)
 			console_start(uport->cons);


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