linux-kernel - Re: [PATCH] i2c: exynos5: Initialise Samsung High Speed I2C controller early

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Message-ID: <20140521102515.GJ2708@katana>
Date:	Wed, 21 May 2014 12:25:15 +0200
From:	Wolfram Sang <wsa@...-dreams.de>
To:	Mark Brown <broonie@...nel.org>
Cc:	Naveen Krishna Ch <naveenkrishna.ch@...il.com>,
	Naveen Krishna Chatradhi <ch.naveen@...sung.com>,
	linux-i2c@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	"linux-samsung-soc@...r.kernel.org" 
	<linux-samsung-soc@...r.kernel.org>, sjg@...omium.org,
	grundler@...omium.org, linux-kernel@...r.kernel.org,
	cpgs@...sung.com
Subject: Re: [PATCH] i2c: exynos5: Initialise Samsung High Speed I2C
 controller early

On Fri, May 09, 2014 at 03:54:25PM +0100, Mark Brown wrote:
> On Fri, May 09, 2014 at 08:12:47PM +0530, Naveen Krishna Ch wrote:
> > On 9 May 2014 19:21, Mark Brown <broonie@...nel.org> wrote:
> > > On Fri, May 09, 2014 at 05:50:00PM +0530, Naveen Krishna Ch wrote:
> 
> > >> DRM related drivers like DP, FIMD, HDMI, Mixer wants to be probed ASAP
> > >> during the boot.
> > >> The real problem comes when, one of these drivers do a regulator_get().
> 
> > >> If the physical supply  is not enabled/hookedup the regulator_get() call
> > >> assumes that physical supply is present and returns a
> > >> "dummy_regulator" (But, not an error).
> 
> > >> Because of which, Display and several other devices fails to work.
> 
> > > These drivers are buggy, if they geniunely expect and handle a missing
> > > supply then they should be using regulator_get_optional() to request the
> > > regulator and even if they don't the use of subsys_initcall() is not
> > > going to fix anything here - if a dummy regulator is going to be
> > > returned the time things are probed won't make a difference.
> 
> ...
> 
> > If all the I2C, SPI, DMA, I2C_TUNNEL, DRM based LCD are all mod_probes()
> > DRM drivers are probing a head of the PMIC probe. Which is causing the
> > display drivers to get "dummy_regulators" instead of the real supplies.
> 
> No, it really won't - I have no idea what you are doing but it's not
> mainline.  If you are getting dummy regulators then you don't have a
> supply present at all and probe ordering isn't going to make a blind
> bit of difference.
> 
> Please provide a specific technical description of the problem you are
> seeing in mainline.

+1 Unless we have a clear understanding that this is the only acceptable
solution in mainline, this is really an out-of-tree patch.


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