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

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Message-ID: <ZrYZ/i1QFhfmv0zi@lpieralisi>
Date: Fri, 9 Aug 2024 15:30:38 +0200
From: Lorenzo Pieralisi <lpieralisi@...nel.org>
To: Elliot Berman <quic_eberman@...cinc.com>
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 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.

Thanks,
Lorenzo

> I'm not sure how best to define the behavior if user sets
> reboot_mode = REBOOT_WARM and then user does "reboot bootloader". IMO,
> "REBOOT_WARM" is at odds with the "bootloader" command. We can have one
> take precedence over the other. I chose for the vendor resets to take
> priority, since if userspace is providing specific command at reboot
> time, that's probably what they want.
> 
> Let me know your thoughts and I'm happy to change the behavior around.
> 
> 
> Thanks,
> Elliot