Re: [PATCH] reboot: add reboot_panic parameter

Re: [PATCH] reboot: add reboot_panic parameter

[Andrew Morton]

On Mon, 2 Jul 2018 02:20:59 +0000 "Tian, Baofeng" <baofeng.tian@intel.com> wrote:

> This "reboot_panic" kernel cmdline parameter allow to change the
> reboot mode in case of panic only. It use the same format as the
> "reboot" parameter.
> Example, for cf9 warm reset in case of panic: reboot_panic=p,w
> currently it only support cold/warm reset in case of panic.

Why should we do this?  What are the benefits, what are the usecases,
etc?  

Some user-facing documentation should clear that up.  `grep -r reboot=
Documentation' will direct you to the appropriate places.

RE: [PATCH] reboot: add reboot_panic parameter

[Tian, Baofeng]

Hi, Morton

On android platform, if use adb reboot, it will automatically reboot with cold reset.
cold reset will reset RAM and cause RAM lose data information, if we want to enable some debug features
like pstore, and ramdump etc, warm reset is needed to keep RAM across reset

So, we add this interface to allow people to set reboot as warm to get log data across reset.

Thanks
Tim

-----Original Message-----
From: Andrew Morton [mailto:akpm@linux-foundation.org] 
Sent: Tuesday, July 3, 2018 5:31 AM
To: Tian, Baofeng <baofeng.tian@intel.com>
Cc: andrew.smirnov@gmail.com; linux-kernel@vger.kernel.org; Zhuang, Qihua <qihua.zhuang@intel.com>
Subject: Re: [PATCH] reboot: add reboot_panic parameter

On Mon, 2 Jul 2018 02:20:59 +0000 "Tian, Baofeng" <baofeng.tian@intel.com> wrote:

> This "reboot_panic" kernel cmdline parameter allow to change the 
> reboot mode in case of panic only. It use the same format as the 
> "reboot" parameter.
> Example, for cf9 warm reset in case of panic: reboot_panic=p,w 
> currently it only support cold/warm reset in case of panic.

Why should we do this?  What are the benefits, what are the usecases, etc?  

Some user-facing documentation should clear that up.  `grep -r reboot= Documentation' will direct you to the appropriate places.

Re: [PATCH] reboot: add reboot_panic parameter

[Andrew Morton]

On Thu, 5 Jul 2018 06:47:37 +0000 "Tian, Baofeng" <baofeng.tian@intel.com> wrote:

> -----Original Message-----
> From: Andrew Morton [mailto:akpm@linux-foundation.org] 
> Sent: Tuesday, July 3, 2018 5:31 AM
> To: Tian, Baofeng <baofeng.tian@intel.com>
> Cc: andrew.smirnov@gmail.com; linux-kernel@vger.kernel.org; Zhuang, Qihua <qihua.zhuang@intel.com>
> Subject: Re: [PATCH] reboot: add reboot_panic parameter
> 
> On Mon, 2 Jul 2018 02:20:59 +0000 "Tian, Baofeng" <baofeng.tian@intel.com> wrote:
> 
> > This "reboot_panic" kernel cmdline parameter allow to change the 
> > reboot mode in case of panic only. It use the same format as the 
> > "reboot" parameter.
> > Example, for cf9 warm reset in case of panic: reboot_panic=p,w 
> > currently it only support cold/warm reset in case of panic.
> 
> Why should we do this?  What are the benefits, what are the usecases, etc?  
> 
> Some user-facing documentation should clear that up.  `grep -r reboot= Documentation' will direct you to the appropriate places.
> 

(top-posting repaired.  Please don't top-post)

> Hi, Morton

"Andrew" :)

> On android platform, if use adb reboot, it will automatically reboot with cold reset.
> cold reset will reset RAM and cause RAM lose data information, if we want to enable some debug features
> like pstore, and ramdump etc, warm reset is needed to keep RAM across reset
> 
> So, we add this interface to allow people to set reboot as warm to get log data across reset.
> 

OK, sounds good.  Please add this info to the changelog, add the user
documentation and resend.