linux-kernel - Re: [RESEND][PATCH v2] firmware/psci: add support for SYSTEM

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Message-ID: <20190411164936.GB5327@e107155-lin>
Date:   Thu, 11 Apr 2019 17:49:36 +0100
From:   Sudeep Holla <sudeep.holla@....com>
To:     "Koskinen, Aaro (Nokia - FI/Espoo)" <aaro.koskinen@...ia.com>
Cc:     "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Aaro Koskinen <aaro.koskinen@....fi>,
        Florian Fainelli <f.fainelli@...il.com>,
        Michal Simek <michal.simek@...inx.com>,
        Mark Rutland <mark.rutland@....com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>
Subject: Re: [RESEND][PATCH v2] firmware/psci: add support for SYSTEM_RESET2

On Thu, Apr 11, 2019 at 11:42:28AM +0000, Koskinen, Aaro (Nokia - FI/Espoo) wrote:
> Hi,
> 
> From: Sudeep Holla [sudeep.holla@....com]:
> >  static void psci_sys_reset(enum reboot_mode reboot_mode, const char *cmd)
> >  {
> > +       if ((reboot_mode == REBOOT_WARM || reboot_mode == REBOOT_SOFT) &&
> 
> I would omit the REBOOT_SOFT here.
>

I included REBOOT_SOFT for 2 reasons:
1. drivers/firmware/efi/reboot.c - efi_reboot treats WARM and SOFT reboots same
2. If the vendors specific reboots are added and handled in EFI, I assume it
   will be categorised under REBOOT_SOFT.

If that's wrong I can drop REBOOT_SOFT.

> > +           psci_system_reset2_supported)
> > +               /*
> > +                * reset_type[31] = 0 (architectural)
> > +                * reset_type[30:0] = 0 (SYSTEM_WARM_RESET)
> > +                * cookie = 0 (ignored by the implementation)
> > +                */
> > +               invoke_psci_fn(PSCI_FN_NATIVE(1_1, SYSTEM_RESET2), 0, 0, 0);
> > +
> >        invoke_psci_fn(PSCI_0_2_FN_SYSTEM_RESET, 0, 0, 0);
>
> Use else here, so that we fall back to system halt if SYSTEM_RESET2 fails.
>

Will that not change current behaviour ? IOW, is that expected behaviour ?
I am not sure if halt can be prefer over cold reboot in absence of warm/soft
reboot when the system is request to reboot. From PSCI perspective, since
SYSTEM_RESET is mandatory I prefer that unless Linux has any restriction
on this behaviour.

--
Regards,
Sudeep