From mboxrd@z Thu Jan 1 00:00:00 1970 From: naveenkrishna.ch@gmail.com (Naveen Krishna Ch) Date: Fri, 9 May 2014 17:50:00 +0530 Subject: [PATCH] i2c: exynos5: Initialise Samsung High Speed I2C controller early In-Reply-To: <20140424162558.GB12304@sirena.org.uk> References: <1398350916-885-1-git-send-email-ch.naveen@samsung.com> <20140424162558.GB12304@sirena.org.uk> Message-ID: To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org Hello Mark, On 24 April 2014 21:55, Mark Brown 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 :)