linux-kernel - Re: [PATCHv2] OMAP: Enable Magic SysRq on serial console ttyOx

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Message-ID: <AANLkTikjdukQ+kUUR7N11rZ5b=Xd=xLb0-chMrbp5BQ6@mail.gmail.com>
Date:	Wed, 19 Jan 2011 19:28:20 +0530
From:	Govindraj <govindraj.ti@...il.com>
To:	Thomas Weber <weber@...science.de>
Cc:	"G, Manjunath Kondaiah" <manjugk@...com>,
	linux-omap@...r.kernel.org, Tony Lindgren <tony@...mide.com>,
	"Govindraj.R" <govindraj.raja@...com>,
	Greg Kroah-Hartman <gregkh@...e.de>,
	Andrei Emeltchenko <andrei.emeltchenko@...ia.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCHv2] OMAP: Enable Magic SysRq on serial console ttyOx

On Wed, Jan 19, 2011 at 7:01 PM, Thomas Weber <weber@...science.de> wrote:
> Am 19.01.2011 14:00, schrieb G, Manjunath Kondaiah:
>> On Wed, Jan 19, 2011 at 03:01:39PM +0530, Govindraj wrote:
>>> On Wed, Jan 19, 2011 at 2:11 PM, Thomas Weber <weber@...science.de> wrote:
>>>> Magic SysRq key is not working for OMAP on new serial
>>>> console ttyOx because SUPPORT_SYSRQ is not defined
>>>> for omap-serial.
>>>>
>>>> This patch defines SUPPORT_SYSRQ in omap-serial and
>>>> enables handling of Magic SysRq character.
>>>>
>>>> Signed-off-by: Thomas Weber <weber@...science.de>
>>>
>>> Looks fine to me.
>>>
>>> Acked-by: Govindraj.R <govindraj.raja@...com>
>> I tried to use SysRq key on minicom after applying this patch, it looks
>> like it is not triggering sysrq event.
>>
>> Am I missing anything?
>>
>> -Manjunath
>> --
> Hello Manjunath,
>
> Do you have CONFIG_MAGIC_SYSRQ enabled?
> Magic SysRq key in Kernel Hacking
>
> I tested it on Devkit8000 (beagle board clone).
>

re-setting lsr_break_flag to 0 in receive chars is causing issues
in getting sysrq key break sequence on omap-serial.c

Manju,

can you try this change on your environment.
With below change works for me on 3430SDP/4430SDP.
key sequence I checked.
[alt + b + t]  => shows trace of tasks running.
[alt + b + b] => system reboot.


diff --git a/drivers/serial/omap-serial.c b/drivers/serial/omap-serial.c
index 1201eff..6df623e 100644
--- a/drivers/serial/omap-serial.c
+++ b/drivers/serial/omap-serial.c
@@ -20,6 +20,10 @@
  * this driver as required for the omap-platform.
  */

+#if defined(CONFIG_SERIAL_OMAP_CONSOLE) && defined(CONFIG_MAGIC_SYSRQ)
+#define SUPPORT_SYSRQ
+#endif
+
 #include <linux/module.h>
 #include <linux/init.h>
 #include <linux/console.h>
@@ -190,7 +194,6 @@ static inline void receive_chars(struct
uart_omap_port *up, int *status)
                        if (up->port.line == up->port.cons->index) {
                                /* Recover the break flag from console xmit */
                                lsr |= up->lsr_break_flag;
-                               up->lsr_break_flag = 0;
                        }
 #endif
                        if (lsr & UART_LSR_BI)


--
Thanks,
Govindraj.R
--
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