Re: [PATCH v4 6/6] PM / Domains: Stop deferring probe at the end of initcall

[Ulf Hansson]

On 10 July 2018 at 16:25, Rob Herring <robh@xxxxxxxxxx> wrote:
> On Mon, Jul 9, 2018 at 4:49 PM Ulf Hansson <ulf.hansson@xxxxxxxxxx> wrote:
>>
>> On 9 July 2018 at 17:41, Rob Herring <robh@xxxxxxxxxx> wrote:
>> > All PM domain drivers must be built-in (at least those using DT), so
>> > there is no point deferring probe after initcalls are done. Continuing
>> > to defer probe may prevent booting successfully even if managing PM
>> > domains is not required. This can happen if the user failed to enable
>> > the driver or if power-domains are added to a platform's DT, but there
>> > is not yet a driver (e.g. a new DTB with an old kernel).
>> >
>> > Call the driver core function driver_deferred_probe_check_init_done()
>> > instead of just returning -EPROBE_DEFER to stop deferring probe when
>> > initcalls are done.
>> >
>> > Acked-by: "Rafael J. Wysocki" <rjw@xxxxxxxxxxxxx>
>> > Cc: Kevin Hilman <khilman@xxxxxxxxxx>
>> > Cc: Ulf Hansson <ulf.hansson@xxxxxxxxxx>
>> > Cc: Pavel Machek <pavel@xxxxxx>
>> > Cc: Len Brown <len.brown@xxxxxxxxx>
>> > Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
>> > Cc: linux-pm@xxxxxxxxxxxxxxx
>> > Signed-off-by: Rob Herring <robh@xxxxxxxxxx>
>> > ---
>> > v4:
>> >  - Add Rafael's ack
>> >
>> > v3:
>> >   - Update to new function name
>> >
>> >  drivers/base/power/domain.c | 2 +-
>> >  1 file changed, 1 insertion(+), 1 deletion(-)
>> >
>> > diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c
>> > index 4925af5c4cf0..8c12213875c6 100644
>> > --- a/drivers/base/power/domain.c
>> > +++ b/drivers/base/power/domain.c
>> > @@ -2253,7 +2253,7 @@ static int __genpd_dev_pm_attach(struct device *dev, struct device_node *np,
>> >                 mutex_unlock(&gpd_list_lock);
>> >                 dev_dbg(dev, "%s() failed to find PM domain: %ld\n",
>> >                         __func__, PTR_ERR(pd));
>> > -               return -EPROBE_DEFER;
>> > +               return driver_deferred_probe_check_state(dev);
>> >         }
>>
>> This isn't the only error path where -EPROBE_DEFER may be returned
>> during attach in genpd.
>
> Yes, but I think this is the only place you can fail to get the PD
> device from DT. The case we care about is properties exist in the DT,
> but no driver exists.

That's correct. Thanks for clarifying!

>
> What would cause deferring in the latter cases?

To power on the PM domain for example, which often is required to be
able to probe the device.

>
> Rob

Kind regards
Uffe