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

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Message-ID: <CAPDyKFp7qNe6Yp62GyRcfc2TBxqqexMxqQkZ-Hc3YFoy-_7ZLw@mail.gmail.com>
Date:   Wed, 11 Jul 2018 11:41:04 +0200
From:   Ulf Hansson <ulf.hansson@...aro.org>
To:     Rob Herring <robh@...nel.org>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Linus Walleij <linus.walleij@...aro.org>,
        Alexander Graf <agraf@...e.de>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Kevin Hilman <khilman@...nel.org>,
        Joerg Roedel <joro@...tes.org>,
        Robin Murphy <robin.murphy@....com>,
        Mark Brown <broonie@...nel.org>,
        Frank Rowand <frowand.list@...il.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        devicetree@...r.kernel.org,
        Architecture Mailman List <boot-architecture@...ts.linaro.org>,
        "moderated list:ARM/FREESCALE IMX / MXC ARM ARCHITECTURE" 
        <linux-arm-kernel@...ts.infradead.org>,
        Pavel Machek <pavel@....cz>, Len Brown <len.brown@...el.com>,
        "open list:THERMAL" <linux-pm@...r.kernel.org>
Subject: Re: [PATCH v4 6/6] PM / Domains: Stop deferring probe at the end of initcall

On 10 July 2018 at 16:25, Rob Herring <robh@...nel.org> wrote:
> On Mon, Jul 9, 2018 at 4:49 PM Ulf Hansson <ulf.hansson@...aro.org> wrote:
>>
>> On 9 July 2018 at 17:41, Rob Herring <robh@...nel.org> 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@...ysocki.net>
>> > Cc: Kevin Hilman <khilman@...nel.org>
>> > Cc: Ulf Hansson <ulf.hansson@...aro.org>
>> > Cc: Pavel Machek <pavel@....cz>
>> > Cc: Len Brown <len.brown@...el.com>
>> > Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
>> > Cc: linux-pm@...r.kernel.org
>> > Signed-off-by: Rob Herring <robh@...nel.org>
>> > ---
>> > 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