From: Naveen Krishna Ch <naveenkrishna.ch@gmail.com>
To: Mark Brown <broonie@kernel.org>
Cc: Naveen Krishna Chatradhi <ch.naveen@samsung.com>,
linux-i2c@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
"linux-samsung-soc@vger.kernel.org"
<linux-samsung-soc@vger.kernel.org>,
sjg@chromium.org, grundler@chromium.org,
linux-kernel@vger.kernel.org, wsa@the-dreams.de,
cpgs@samsung.com
Subject: Re: [PATCH] i2c: exynos5: Initialise Samsung High Speed I2C controller early
Date: Fri, 9 May 2014 17:50:00 +0530 [thread overview]
Message-ID: <CAHfPSqB5+mLiC07jbEpeUgW63pZVk700SkYGxToO7GRAsFm_nQ@mail.gmail.com> (raw)
In-Reply-To: <20140424162558.GB12304@sirena.org.uk>
Hello Mark,
On 24 April 2014 21:55, Mark Brown <broonie@kernel.org> wrote:
> On Thu, Apr 24, 2014 at 08:18:36PM +0530, Naveen Krishna Chatradhi wrote:
>> This patch moves initialization code to subsys_initcall() to ensure
>> that the i2c bus is available early so the regulators can be quickly
>> probed and available for other devices on their probe() call.
>
>> Such solution has been proposed by Mark Brown to fix the problem of
>> the regulators not beeing available on the peripheral device probe():
>> http://lists.infradead.org/pipermail/linux-arm-kernel/2010-March/011971.html
>
> What specifically is this needed for? We *should* be able to use
> deferred probe for most things, but I know that not all subsystems are
> able to yet.
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.
I2C, I2C_TUNNEL, SPI and DMA drivers are required as subsys_initcall()
for similar reason.
--
Shine bright,
(: Nav :)
next prev parent reply other threads:[~2014-05-09 12:20 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-04-24 14:48 [PATCH] i2c: exynos5: Initialise Samsung High Speed I2C controller early Naveen Krishna Chatradhi
2014-04-24 16:25 ` Mark Brown
2014-04-25 4:58 ` Tushar Behera
2014-05-09 12:20 ` Naveen Krishna Ch [this message]
2014-05-09 13:51 ` Mark Brown
2014-05-09 14:42 ` Naveen Krishna Ch
2014-05-09 14:54 ` Mark Brown
2014-05-21 10:25 ` Wolfram Sang
2014-05-21 12:04 ` Naveen Krishna Ch
2014-05-21 13:00 ` Wolfram Sang
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