From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tony Lindgren Subject: Re: [PATCH 2/2] arm: dt: Add device tree support for i2c instance 1 on exynos4 dt machine Date: Fri, 22 Jul 2011 00:12:49 -0700 Message-ID: <20110722071249.GK5783@atomide.com> References: <1310950241-13602-1-git-send-email-thomas.abraham@linaro.org> <1310950241-13602-3-git-send-email-thomas.abraham@linaro.org> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: Content-Disposition: inline In-Reply-To: Sender: linux-samsung-soc-owner@vger.kernel.org To: "G, Manjunath Kondaiah" Cc: Grant Likely , "G, Manjunath Kondaiah" , Thomas Abraham , devicetree-discuss@lists.ozlabs.org, linux-samsung-soc@vger.kernel.org, linux-i2c@vger.kernel.org, ben-linux@fluff.org, patches@linaro.org List-Id: linux-i2c@vger.kernel.org * G, Manjunath Kondaiah [110719 09:59]: > On Tue, Jul 19, 2011 at 2:00 AM, Grant Likely wrote: > > > > No, the i2c bus node should still appear in the SoC .dtsi file. =C2= =A0If a > > board doesn't use a particular i2c bus, then the board.dts file can > > add a status =3D "disabled"; property to the i2c bus node to disabl= e it. >=20 > that's right. I am referring to I2C slave devices. For a given SoC, > two different > boards can have different i2c slave devices with different slave > address. In that case, > it is better to have i2c child/slave nodes in board .dts file. This is OK for now, but from bus/hwmod point of view we need to reset a= ll the unused devices as otherwise PM will never work properly. Disabling each device in the board .dts file will never be done correct= ly for most boards.. And on each board, probably 2/3 of the devices are un= used because of the pin limitations :) So the disabling of unused devices should be done with a late_initcall = and controlled by kernel cmdline. We were thinking hwmod.disable=3D[0|1]. The late_initcall to disable unused device tree devices could also be added later on to device tree core code. Regards, Tony