linux-kernel - Re: [PATCH v4 6/6] regulator: Use driver_deferred_probe_timeout for regulator_init_complete

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Message-ID: <20200220160522.GH955802@ripper>
Date:   Thu, 20 Feb 2020 08:05:22 -0800
From:   Bjorn Andersson <bjorn.andersson@...aro.org>
To:     John Stultz <john.stultz@...aro.org>
Cc:     lkml <linux-kernel@...r.kernel.org>, Rob Herring <robh@...nel.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Kevin Hilman <khilman@...nel.org>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Pavel Machek <pavel@....cz>, Len Brown <len.brown@...el.com>,
        Todd Kjos <tkjos@...gle.com>,
        Liam Girdwood <lgirdwood@...il.com>,
        Mark Brown <broonie@...nel.org>,
        Thierry Reding <treding@...dia.com>,
        Linus Walleij <linus.walleij@...aro.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-pm@...r.kernel.org
Subject: Re: [PATCH v4 6/6] regulator: Use driver_deferred_probe_timeout for
 regulator_init_complete_work

On Wed 19 Feb 21:04 PST 2020, John Stultz wrote:

> The regulator_init_complete_work logic defers the cleanup for an
> arbitrary 30 seconds of time to allow modules loaded by userland
> to start.
> 
> This arbitrary timeout is similar to the
> driver_deferred_probe_timeout value, and its been suggested we
> align these so users have a method to extend the timeouts as
> needed.
> 
> So this patch changes the logic to use the
> driver_deferred_probe_timeout value if it is set, otherwise we
> directly call the regulator_init_complete_work_function().
> 
> Cc: Rob Herring <robh@...nel.org>
> Cc: "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: Todd Kjos <tkjos@...gle.com>
> Cc: Bjorn Andersson <bjorn.andersson@...aro.org>
> Cc: Liam Girdwood <lgirdwood@...il.com>
> Cc: Mark Brown <broonie@...nel.org>
> Cc: Thierry Reding <treding@...dia.com>
> Cc: Linus Walleij <linus.walleij@...aro.org>
> Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> Cc: linux-pm@...r.kernel.org
> Signed-off-by: John Stultz <john.stultz@...aro.org>
> Change-Id: I9fa2411abbb91ed4dd0edc41e8cc8583577c005b

Change-Id...

> ---
> v4:
> * Split out into its own patch, as suggested by Mark
> ---
>  drivers/regulator/core.c | 25 ++++++++++++++-----------
>  1 file changed, 14 insertions(+), 11 deletions(-)
> 
> diff --git a/drivers/regulator/core.c b/drivers/regulator/core.c
> index d015d99cb59d..394e7b11576a 100644
> --- a/drivers/regulator/core.c
> +++ b/drivers/regulator/core.c
> @@ -5767,18 +5767,21 @@ static int __init regulator_init_complete(void)
>  		has_full_constraints = true;
>  
>  	/*
> -	 * We punt completion for an arbitrary amount of time since
> -	 * systems like distros will load many drivers from userspace
> -	 * so consumers might not always be ready yet, this is
> -	 * particularly an issue with laptops where this might bounce
> -	 * the display off then on.  Ideally we'd get a notification
> -	 * from userspace when this happens but we don't so just wait
> -	 * a bit and hope we waited long enough.  It'd be better if
> -	 * we'd only do this on systems that need it, and a kernel
> -	 * command line option might be useful.
> +	 * If driver_deferred_probe_timeout is set, we punt
> +	 * completion for that many seconds since systems like
> +	 * distros will load many drivers from userspace so consumers
> +	 * might not always be ready yet, this is particularly an
> +	 * issue with laptops where this might bounce the display off
> +	 * then on.  Ideally we'd get a notification from userspace
> +	 * when this happens but we don't so just wait a bit and hope
> +	 * we waited long enough.  It'd be better if we'd only do
> +	 * this on systems that need it.
>  	 */
> -	schedule_delayed_work(&regulator_init_complete_work,
> -			      msecs_to_jiffies(30000));
> +	if (driver_deferred_probe_timeout >= 0)
> +		schedule_delayed_work(&regulator_init_complete_work,
> +				      driver_deferred_probe_timeout * HZ);
> +	else
> +		regulator_init_complete_work_function(NULL);

Why not schedule_delayed_work(..., 0) in this case, to get it off the
initcall context and to avoid the difference in execution paths?

Regards,
Bjorn

>  
>  	return 0;
>  }
> -- 
> 2.17.1
>