linux-kernel - Re: PSCI version 1.1 and SYSTEM

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Message-ID: <20190501094953.GA21851@e107155-lin>
Date:   Wed, 1 May 2019 10:49:53 +0100
From:   Sudeep Holla <sudeep.holla@....com>
To:     Sodagudi Prasad <psodagud@...eaurora.org>
Cc:     julien.thierry@....com, will.deacon@....com,
        catalin.marinas@....com, mark.rutland@....com,
        lorenzo.pieralisi@....com, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, Sudeep Holla <sudeep.holla@....com>
Subject: Re: PSCI version 1.1 and SYSTEM_RESET2

On Tue, Apr 30, 2019 at 05:07:31PM -0700, Sodagudi Prasad wrote:
> On 2019-04-30 14:44, Sodagudi Prasad wrote:
> +Sudeep
>
> > Hi Mark/Will,
> >
> > I would like to understand whether ARM linux community have plans to
> > support PSCI version 1.1 or not.
> > PSCI_1_1 specification introduced support for SYSTEM_RESET2 command
> > and this new command helps mobile devices to SYSTEM_WARM_RESET
> > support. Rebooting devices with warm reboot helps to capture the
> > snapshot of the ram contents for post-mortem analysis.
>
> I think, there is a recent discussion from Sudeep for the SYSTEM_RESET2
> support.
> https://patchwork.kernel.org/patch/10884345/
>

This has landed in -next, and hopefully must appear in v5.2

>
> Hi Sudeep,
>
> I was going through your discussion in the below list -
> https://lore.kernel.org/lkml/d73d3580-4ec1-a281-4585-5c776fc08c79@xilinx.com/
>
> There is no provision to set up reboot mode dynamically instead kernel
> command line parameter.
> Looking for options to reboot device with warm reboot option when kernel
> crashed.
>
> panic() --> emergency_restart() --> machine_emergency_restart() -->
> machine_restart(NULL);
>
> It would nice if there is a config option to reboot the device either in
> warm or cold in the case of kernel panic.

I presume you prefer to do warm boot in case of panic to get a dump of
the memory to inspect ? If so, is kexec/kdump not the mechanism to
achieve that ?

I am just trying to understand the use case. Xilinx asked for the same
but never got to understand their use case.

--
Regards,
Sudeep