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

[Lorenzo Pieralisi <lpieralisi@kernel.org>]

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