linux-kernel - Re: [RFC][PATCH] pinctrl: Rework driver_deferred_probe_check_state() evaluation since default timeout has changed

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Date:   Fri, 28 Aug 2020 00:42:46 +0200
From:   Linus Walleij <linus.walleij@...aro.org>
To:     John Stultz <john.stultz@...aro.org>
Cc:     lkml <linux-kernel@...r.kernel.org>,
        Linux PM list <linux-pm@...r.kernel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Thierry Reding <treding@...dia.com>,
        Mark Brown <broonie@...nel.org>,
        Liam Girdwood <lgirdwood@...il.com>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Saravana Kannan <saravanak@...gle.com>,
        Todd Kjos <tkjos@...gle.com>, Len Brown <len.brown@...el.com>,
        Pavel Machek <pavel@....cz>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Kevin Hilman <khilman@...nel.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Rob Herring <robh@...nel.org>
Subject: Re: [RFC][PATCH] pinctrl: Rework driver_deferred_probe_check_state()
 evaluation since default timeout has changed

On Sat, Aug 8, 2020 at 6:35 AM John Stultz <john.stultz@...aro.org> wrote:

> In commit bec6c0ecb243 ("pinctrl: Remove use of
> driver_deferred_probe_check_state_continue()"), we removed the
> use of driver_deferred_probe_check_state_continue() which
> effectively never returned -ETIMED_OUT, with the
> driver_deferred_probe_check_state() function that had been
> reworked to properly return ETIMED_OUT when the deferred probe
> timeout expired. Along with that change, we set the default
> timeout to 30 seconds.
>
> However, since moving the timeout to 30 seconds caused some
> issues for some users with optional dt links, we set the
> default timeout back to zero - see commit ce68929f07de ("driver
> core: Revert default driver_deferred_probe_timeout value to 0")
>
> This in essence changed the behavior of the pinctrl's usage
> of driver_deferred_probe_check_state(), as it now would return
> ETIMED_OUT by default. Thierry reported this caused problems with
> resume on tegra platforms.
>
> Thus this patch tweaks the pinctrl logic so that it behaves as
> before. If modules are enabled, we'll only return EPROBE_DEFERRED
> while we're missing drivers linked in the DT.
>
> Cc: linux-pm@...r.kernel.org
> Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> Cc: Linus Walleij <linus.walleij@...aro.org>
> Cc: Thierry Reding <treding@...dia.com>
> Cc: Mark Brown <broonie@...nel.org>
> Cc: Liam Girdwood <lgirdwood@...il.com>
> Cc: Bjorn Andersson <bjorn.andersson@...aro.org>
> Cc: Saravana Kannan <saravanak@...gle.com>
> Cc: Todd Kjos <tkjos@...gle.com>
> Cc: Len Brown <len.brown@...el.com>
> Cc: Pavel Machek <pavel@....cz>
> Cc: Ulf Hansson <ulf.hansson@...aro.org>
> Cc: Kevin Hilman <khilman@...nel.org>
> Cc: "Rafael J. Wysocki" <rjw@...ysocki.net>
> Cc: Rob Herring <robh@...nel.org>
> Fixes: bec6c0ecb243 ("pinctrl: Remove use of driver_deferred_probe_check_state_continue()")
> Fixes: ce68929f07de ("driver core: Revert default driver_deferred_probe_timeout value to 0")
> Reported-by: Thierry Reding <thierry.reding@...il.com>
> Signed-off-by: John Stultz <john.stultz@...aro.org>

This looks sensible to me, but I'm not the best with the device core.
It'd be good to have some Greg or Rafael stamp on this.

Can we have some comments? Reviewed-by?

Yours,
Linus Walleij