linux-kernel - Re: [PATCH] of/platform: add initcall

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Date:   Tue, 19 Jun 2018 08:33:46 -0600
From:   Rob Herring <robh+dt@...nel.org>
To:     Todd Poynor <toddpoynor@...il.com>
Cc:     Frank Rowand <frowand.list@...il.com>, devicetree@...r.kernel.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Android Kernel Team <kernel-team@...roid.com>,
        Todd Poynor <toddpoynor@...gle.com>
Subject: Re: [PATCH] of/platform: add initcall_debug logs for device creates

On Mon, Jun 18, 2018 at 7:46 PM, Todd Poynor <toddpoynor@...il.com> wrote:
> From: Todd Poynor <toddpoynor@...gle.com>
>
> Add initcall_debug logs for the amount of time taken by each OF platform
> bus device create call.  For example:
>
>    of platform device create /reserved-memory/ramoops@...00000 took
>    3255 usecs
>
> initcall_debug already reports the total of all such device creates
> as a single entry for function of_platform_default_populate_init (or
> similar, depending on the board).  The new logs help identify which of
> the potentially hundreds of device inits take significant amounts of
> time.

It's really the probe time that matters here. Outside of that,
creating the devices should be fairly constant time. So why not add
timing around non bus specific probe code (driver_probe_device)
instead of adding this in multiple places. Then you can remove the
timing from deferred probe code.

Rob