linux-kernel - Re: [PATCH v6 3/5] firmware: psci: Read and use vendor reset types

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Message-ID: <20241023151556009-0700.eberman@hu-eberman-lv.qualcomm.com>
Date: Wed, 23 Oct 2024 15:16:38 -0700
From: Elliot Berman <quic_eberman@...cinc.com>
To: Stephen Boyd <swboyd@...omium.org>
CC: Andy Yan <andy.yan@...k-chips.com>, Arnd Bergmann <arnd@...db.de>,
        "Bartosz Golaszewski" <bartosz.golaszewski@...aro.org>,
        Bjorn Andersson
	<andersson@...nel.org>,
        Catalin Marinas <catalin.marinas@....com>,
        "Conor
 Dooley" <conor+dt@...nel.org>,
        Konrad Dybcio <konradybcio@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Krzysztof Kozlowski
	<krzysztof.kozlowski+dt@...aro.org>,
        Lorenzo Pieralisi
	<lpieralisi@...nel.org>,
        Mark Rutland <mark.rutland@....com>, Olof Johansson
	<olof@...om.net>,
        Rob Herring <robh@...nel.org>, Sebastian Reichel
	<sre@...nel.org>,
        Vinod Koul <vkoul@...nel.org>, Will Deacon
	<will@...nel.org>,
        <cros-qcom-dts-watchers@...omium.org>,
        "Satya Durga
 Srinivasu Prabhala" <quic_satyap@...cinc.com>,
        Melody Olvera
	<quic_molvera@...cinc.com>,
        Shivendra Pratap <quic_spratap@...cinc.com>,
        <devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        Florian Fainelli
	<florian.fainelli@...adcom.com>,
        <linux-pm@...r.kernel.org>, <linux-arm-msm@...r.kernel.org>
Subject: Re: [PATCH v6 3/5] firmware: psci: Read and use vendor reset types

On Wed, Oct 23, 2024 at 12:02:19PM -0700, Stephen Boyd wrote:
> Quoting Elliot Berman (2024-10-23 09:30:21)
> > On Fri, Oct 18, 2024 at 10:42:46PM -0700, Stephen Boyd wrote:
> > > Quoting Elliot Berman (2024-10-18 12:39:48)
> > > > diff --git a/drivers/firmware/psci/psci.c b/drivers/firmware/psci/psci.c
> > > > index 2328ca58bba6..60bc285622ce 100644
> > > > --- a/drivers/firmware/psci/psci.c
> > > > +++ b/drivers/firmware/psci/psci.c
> > > > @@ -305,9 +315,29 @@ static int get_set_conduit_method(const struct device_node *np)
> > > >         return 0;
> > > >  }
> > > >
> > > > +static void psci_vendor_sys_reset2(unsigned long action, void *data)
> > > > +{
> > > > +       const char *cmd = data;
> > > > +       unsigned long ret;
> > > > +       size_t i;
> > > > +
> > > > +       for (i = 0; i < num_psci_reset_params; i++) {
> > > > +               if (!strcmp(psci_reset_params[i].mode, cmd)) {
> > > > +                       ret = invoke_psci_fn(PSCI_FN_NATIVE(1_1, SYSTEM_RESET2),
> > > > +                                            psci_reset_params[i].reset_type,
> > > > +                                            psci_reset_params[i].cookie, 0);
> > > > +                       pr_err("failed to perform reset \"%s\": %ld\n",
> > > > +                               cmd, (long)ret);
> > >
> > > Do this intentionally return? Should it be some other function that's
> > > __noreturn instead and a while (1) if the firmware returns back to the
> > > kernel?
> > >
> >
> > Yes, I think it's best to make sure we fall back to the architectural
> > reset (whether it's the SYSTEM_RESET or architectural SYSTEM_RESET2)
> > since device would reboot then.
> 
> Ok. Please add a comment in the code so we know that it's intentional.
> 
> >
> > > > +               }
> > > > +       }
> > > > +}
> > > > +
> > > >  static int psci_sys_reset(struct notifier_block *nb, unsigned long action,
> > > >                           void *data)
> > > >  {
> > > > +       if (data && num_psci_reset_params)
> > > > +               psci_vendor_sys_reset2(action, data);
> > > > +
> 
> I'd add a comment here as well indicating that a fallback is used.
> 

Ack.

Thanks for the feedback!

- Elliot