linux-kernel - Re: [PATCH 1/5] pinctrl: core: Use delayed work for hogs

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Date:   Fri, 2 Dec 2016 14:08:30 +0100
From:   Linus Walleij <linus.walleij@...aro.org>
To:     Tony Lindgren <tony@...mide.com>
Cc:     Haojian Zhuang <haojian.zhuang@...aro.org>,
        Masahiro Yamada <yamada.masahiro@...ionext.com>,
        Grygorii Strashko <grygorii.strashko@...com>,
        Nishanth Menon <nm@...com>,
        "linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Linux-OMAP <linux-omap@...r.kernel.org>
Subject: Re: [PATCH 1/5] pinctrl: core: Use delayed work for hogs

On Tue, Nov 15, 2016 at 6:08 PM, Tony Lindgren <tony@...mide.com> wrote:
> * Tony Lindgren <tony@...mide.com> [161115 07:42]:
>> * Linus Walleij <linus.walleij@...aro.org> [161114 22:53]:
>> > On Tue, Nov 15, 2016 at 1:47 AM, Tony Lindgren <tony@...mide.com> wrote:
>> >
>> > > 8< --------------------------------
>> > > From tony Mon Sep 17 00:00:00 2001
>> > > From: Tony Lindgren <tony@...mide.com>
>> > > Date: Tue, 25 Oct 2016 08:33:35 -0700
>> > > Subject: [PATCH] pinctrl: core: Use delayed work for hogs
>> > >
>> > > Having the pin control framework call pin controller functions
>> > > before it's probe has finished is not nice as the pin controller
>> > > device driver does not yet have struct pinctrl_dev handle.
>> > >
>> > > Let's fix this issue by adding deferred work for late init. This is
>> > > needed to be able to add pinctrl generic helper functions that expect
>> > > to know struct pinctrl_dev handle. Note that we now need to call
>> > > create_pinctrl() directly as we don't want to add the pin controller
>> > > to the list of controllers until the hogs are claimed. We also need
>> > > to pass the pinctrl_dev to the device tree parser functions as they
>> > > otherwise won't find the right controller at this point.
>> > >
>> > > Signed-off-by: Tony Lindgren <tony@...mide.com>
>> >
>> > This looks a lot better!
>> >
>> > So if I understand correctly, we can guarantee that the delayed
>> > work will not execute until the device driver probe() has finished,
>> > and it *will* execute immediately after that?
>> >
>> > So:
>> > - Device driver probes
>> > - Delayed work is called
>> > - Next initcall
>> >
>> > I'm not 100% familiar with how delayed work works... :/
>>
>> Yeah well the delayed work gets scheduled for next jiffy but may
>> be pre-empted as it runs in process context.
>>
>> So in the worst case it could that we still may need to fix few
>> drivers to support -EPROBE_DEFER. I wonder if we should check for
>> hogs in probe already and only defer if hogs are defined?
>
> Below is a version using delayed_work only if pinctrl_dt_has_hogs().
>
> Not sure if testing only for pinctrl-0 is enough there though?

Sorry for the lack of attention to this patch set on my part. :(

Do you think you could resend these last 5 patches after the
release of v4.10-rc1 so we merge it early for the next cycle
and people get a chance to test and see if it works well for
everyone?

I'm worried about adding it to the tree this late in the kernel
cycle...

However I like the look of the series overall a lot.

Yours,
Linus Walleij