Date:	Sun, 18 Oct 2015 12:37:57 -0700
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	Mark Brown <broonie@...nel.org>
Cc:	Tomeu Vizoso <tomeu.vizoso@...labora.com>,
	Rob Herring <robh+dt@...nel.org>,
	Russell King <linux@....linux.org.uk>,
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	Stephen Boyd <sboyd@...eaurora.org>,
	Vinod Koul <vinod.koul@...el.com>,
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	Linus Walleij <linus.walleij@...aro.org>,
	Alexandre Courbot <gnurou@...il.com>,
	Thierry Reding <thierry.reding@...il.com>,
	David Airlie <airlied@...ux.ie>,
	Terje Bergström <tbergstrom@...dia.com>,
	Stephen Warren <swarren@...dotorg.org>,
	Wolfram Sang <wsa@...-dreams.de>,
	Frank Rowand <frowand.list@...il.com>,
	Grant Likely <grant.likely@...aro.org>,
	Kishon Vijay Abraham I <kishon@...com>,
	Sebastian Reichel <sre@...nel.org>,
	Dmitry Eremin-Solenikov <dbaryshkov@...il.com>,
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	Lee Jones <lee.jones@...aro.org>,
	Jean-Christophe Plagniol-Villard <plagnioj@...osoft.com>,
	Tomi Valkeinen <tomi.valkeinen@...com>,
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Subject: Re: [GIT PULL] On-demand device probing

On Sun, Oct 18, 2015 at 08:29:31PM +0100, Mark Brown wrote:
> On Fri, Oct 16, 2015 at 11:57:50PM -0700, Greg Kroah-Hartman wrote:
> 
> > I can't see adding calls like this all over the tree just to solve a
> > bus-specific problem, you are adding of_* calls where they aren't
> > needed, or wanted, at all.
> 
> This isn't bus specific, I'm not sure what makes you say that?

You are making it bus-specific by putting these calls all over the tree
in different bus subsystems semi-randomly for all I can determine.

> > What is the root-problem of your delay in device probing?  I read your
> > last patch series and I can't seem to figure out what the issue is that
> > this is solving in any "better" way from the existing deferred probing.
> 
> So, I don't actually have any platforms that are especially bothered by
> this (at least not for my use cases) so there's a bit of educated
> guessing going on here but there's two broad things I'm aware of.  
> 
> One is that regardless of the actual performance of the system when
> deferred probe goes off it splats errors all over the console which
> makes it look like something is going wrong even if everything is fine
> in the end.  If lots of deferred probing happens then the volume gets
> big too.  People find this distracting, noisy and ugly - it obscures
> actual issues and trains people to ignore errors.  I do think this is a
> reasonable concern and that it's worth trying to mitigate against
> deferral for this reason alone.  We don't want to just ignore the errors
> and not print anything either since if the resource doesn't appear the
> user needs to know what is preventing the driver from instantiating so
> they can try to fix it.

This has come up many times, I have no objection to just turning that
message into a debug message that can be dynamically enabled for those
people wanting to debug their systems for boot time issues.

Please send a patch to do so.

thanks,

greg k-h
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