From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Date: Thu, 31 Jul 2008 13:14:51 -0600 From: Grant Likely To: Timur Tabi Subject: Re: [PATCH] powerpc: i2c-mpc: make speed registers configurable via FDT Message-ID: <20080731191451.GC29097@secretlab.ca> References: <20080727012722.GH12191@secretlab.ca> <4891A744.6060005@grandegger.com> <9e4733910807310849g7e5612dbk9536733e061af8ad@mail.gmail.com> <4891F4D8.9090905@grandegger.com> <4891FC3A.7040609@freescale.com> <20080731180959.GA29057@secretlab.ca> <489200B6.9060906@freescale.com> <20080731182810.GB29097@secretlab.ca> <48920607.5040606@freescale.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <48920607.5040606@freescale.com> Sender: Grant Likely Cc: Scott Wood , Linuxppc-dev@ozlabs.org, Linux I2C List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Thu, Jul 31, 2008 at 01:35:51PM -0500, Timur Tabi wrote: > Grant Likely wrote: > > > No it doesn't, it depends on the register interface to decide > > compatibility. Clock interface is part of that. > > I don't think so. The interface for programming the clock registers is > identical on all 8[356]xx parts. The only thing that matters is what specific > values to put in the FDR and DFSR registers to get a desired I2C bus speed. > That answer is dependent on the actual clock input to the device, which is > external to the device. I wouldn't call the input frequency a property of the > I2C device. Okay, I accept that argument. Make input frequency a property and be done with it. > > I suggested encoding > > the clock divider directly in compatible (implicit in the SoC version), > > but it doesn't have to be that way. If clock freq is obtained from > > another property or some other method then that is okay too. > > I think we agree on that. indeed. > > There is nothing wrong with it (as long as we agree and it gets > > documented). I certainly don't have a problem with doing it this way. > > I propose the property "clock-frequency", like this: > > i2c@3000 { > #address-cells = <1>; > #size-cells = <0>; > cell-index = <0>; > compatible = "fsl-i2c"; > reg = <0x3000 0x100>; > interrupts = <14 0x8>; > interrupt-parent = <&ipic>; > dfsrr; > clock-frequency = <0xblablabla>; <-- added by U-Boot > }; I'm okay with this. > Note that the dfsrr property already differentiates between 8xxx and 52xx, so > maybe we don't need any other device tree changes. The whole dfsrr property is a really bad idea, and it just replaces the equally bad idea of an "mpc5200-clocking" property which is currently in use. This bit should definitely be determined via compatible. g.