linux-kernel - Re: [PATCH v5 3/4] firmware: psci: Read and use vendor reset types

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Message-ID: <20240809090339647-0700.eberman@hu-eberman-lv.qualcomm.com>
Date: Fri, 9 Aug 2024 09:58:31 -0700
From: Elliot Berman <quic_eberman@...cinc.com>
To: Lorenzo Pieralisi <lpieralisi@...nel.org>
CC: Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio
	<konrad.dybcio@...aro.org>,
        Sebastian Reichel <sre@...nel.org>, Rob Herring
	<robh@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>, Vinod Koul <vkoul@...nel.org>,
        Andy Yan
	<andy.yan@...k-chips.com>,
        Mark Rutland <mark.rutland@....com>,
        "Bartosz
 Golaszewski" <bartosz.golaszewski@...aro.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 v5 3/4] firmware: psci: Read and use vendor reset types

On Fri, Aug 09, 2024 at 03:30:38PM +0200, Lorenzo Pieralisi wrote:
> On Wed, Aug 07, 2024 at 11:10:50AM -0700, Elliot Berman wrote:
> 
> [...]
> 
> > > > +static void psci_vendor_sys_reset2(unsigned long action, void *data)
> > > 
> > > 'action' is unused and therefore it is not really needed.
> > > 
> > > > +{
> > > > +	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);
> > > > +		}
> > > > +	}
> > > > +}
> > > > +
> > > >  static int psci_sys_reset(struct notifier_block *nb, unsigned long action,
> > > >  			  void *data)
> > > >  {
> > > > +	if (data && num_psci_reset_params)
> > > 
> > > So, reboot_mode here is basically ignored; if there is a vendor defined
> > > reset, we fire it off.
> > > 
> > > I think Mark mentioned his concerns earlier related to REBOOT_* mode and
> > > reset type (granted, the context was different):
> > > 
> > > https://lore.kernel.org/all/20200320120105.GA36658@C02TD0UTHF1T.local/
> > > 
> > > I would like to understand if this is the right thing to do before
> > > accepting this patchset.
> > > 
> > 
> > I don't have any concerns to move this part below checking reboot_mode.
> > Or, I could add reboot_mode == REBOOT_COLD check.
> 
> The question is how can we map vendor specific reboot magic to Linux
> reboot modes sensibly in generic PSCI code - that's by definition
> vendor specific.
> 

I don't think it's a reasonable thing to do. "reboot bootloader" or
"reboot edl" don't make sense to the Linux reboot modes.

I believe the Linux reboot modes enum is oriented to perspective of
Linux itself and the vendor resets are oriented towards behavior of the
SoC.

Thanks,
Elliot