Re: [PATCH 3/6] ARM: PSCI: Register with kernel restart handler

[Guenter Roeck]

On 04/13/2016 04:05 AM, Mark Rutland wrote:
> On Fri, Apr 08, 2016 at 05:53:56AM -0700, Guenter Roeck wrote:
> > Register with kernel restart handler instead of setting arm_pm_restart
> > directly. This enables support for replacing the PSCI restart handler
> > with a different handler if necessary for a specific board.
> >
> > Select a priority of 129 to indicate a higher than default priority, but
> > keep it as low as possible since PSCI reset is known to fail on some
> > boards.
>
> For reference, which boards?
Salvator-X, reported by Geert Uytterhoeven. Wolfram Sang also reported
that it is broken on a board he is using, but I don't recall if it is
the same board.

> It's unfortunate that that a PSCI 0.2+ implementation would be lacking a
> working SYSTEM_RESET implementation, and it's certainly a mistake to
> discourage.
>
> > Signed-off-by: Guenter Roeck <linux@xxxxxxxxxxxx>
> > ---
> > It might make sense to introduce a restart-priority property for devicetree
> > based configurations, but I am not sure if this would be acceptable.
>
> > From the DT side, I'm not keen on properties for priorities. They're
> incredibly fragile and don't really encode a HW property.
Depends. It is a convenient means to say "primary restart method" or
"may be broken".

> A better option would be to have a property to describe how the PSCI
> implementation is broken (e.g. broken-system-reset), and not register
> the handler at all in that case.
... just like this. I'll look into it.

Thanks,
Guenter

> Thanks,
> Mark.
>
> >   drivers/firmware/psci.c | 11 +++++++++--
> >   1 file changed, 9 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/firmware/psci.c b/drivers/firmware/psci.c
> > index 11bfee8b79a9..99fab3ac3fd5 100644
> > --- a/drivers/firmware/psci.c
> > +++ b/drivers/firmware/psci.c
> > @@ -231,11 +231,18 @@ static int get_set_conduit_method(struct device_node *np)
> >   	return 0;
> >   }
> >
> > -static void psci_sys_reset(enum reboot_mode reboot_mode, const char *cmd)
> > +static int psci_sys_reset(struct notifier_block *np, unsigned long action,
> > +			  void *data)
> >   {
> >   	invoke_psci_fn(PSCI_0_2_FN_SYSTEM_RESET, 0, 0, 0);
> > +	return NOTIFY_DONE;
> >   }
> >
> > +static struct notifier_block psci_sys_reset_nb = {
> > +	.notifier_call = psci_sys_reset,
> > +	.priority = 129,
> > +};
> > +
> >   static void psci_sys_poweroff(void)
> >   {
> >   	invoke_psci_fn(PSCI_0_2_FN_SYSTEM_OFF, 0, 0, 0);
> > @@ -461,7 +468,7 @@ static void __init psci_0_2_set_functions(void)
> >
> >   	psci_ops.migrate_info_type = psci_migrate_info_type;
> >
> > -	arm_pm_restart = psci_sys_reset;
> > +	register_restart_handler(&psci_sys_reset_nb);
> >
> >   	pm_power_off = psci_sys_poweroff;
> >   }
> > --
> > 2.5.0