Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757710Ab2FQRnQ (ORCPT ); Sun, 17 Jun 2012 13:43:16 -0400 Received: from mail-qc0-f174.google.com ([209.85.216.174]:55316 "EHLO mail-qc0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757647Ab2FQRnO convert rfc822-to-8bit (ORCPT ); Sun, 17 Jun 2012 13:43:14 -0400 MIME-Version: 1.0 In-Reply-To: <4FDB3642.5030804@linaro.org> References: <1339428307-3850-1-git-send-email-lee.jones@linaro.org> <1339428307-3850-10-git-send-email-lee.jones@linaro.org> <4FD8BAD2.50703@linaro.org> <4FDAFA17.6050502@linaro.org> <20120615115042.GA27480@bnru02> <4FDB2E57.4030904@linaro.org> <20120615130544.GA28537@bnru02> <4FDB3642.5030804@linaro.org> Date: Sun, 17 Jun 2012 19:43:13 +0200 Message-ID: Subject: Re: Fwd: [PATCH 1/3] i2c: Add Device Tree support to the Nomadik I2C driver From: Linus Walleij To: Lee Jones Cc: Srinidhi Kasagar , Linus WALLEIJ , "arnd@arndb.de" , "linux-kernel@vger.kernel.org" , "grant.likely@secretlab.ca" , "linux-arm-kernel@lists.infradead.org" , "linux-i2c@vger.kernel.org" Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2593 Lines: 68 Gah, what a thread... On Fri, Jun 15, 2012 at 3:18 PM, Lee Jones wrote: > On 15/06/12 14:05, Srinidhi Kasagar wrote: >> On Fri, Jun 15, 2012 at 14:45:11 +0200, Lee Jones wrote: >>> On 15/06/12 12:50, Srinidhi Kasagar wrote: >>>>> +static struct nmk_i2c_controller u8500_i2c = { >>>>> + ? ? ? /* >>>>> + ? ? ? ?* Slave data setup time; 250ns, 100ns, and 10ns, which >>>>> + ? ? ? ?* is 14, 6 and 2 respectively for a 48Mhz i2c clock. >>>>> + ? ? ? ?*/ >>>>> + ? ? ? .slsu ? ? ? ? ? = 0xe, >>>>> + ? ? ? .tft ? ? ? ? ? ?= 1, ? ? ?/* Tx FIFO threshold */ >>>>> + ? ? ? .rft ? ? ? ? ? ?= 8, ? ? ?/* Rx FIFO threshold */ >>>>> + ? ? ? .clk_freq ? ? ? = 100000, /* std. mode operation */ >>>>> + ? ? ? .timeout ? ? ? ?= 200, ? ?/* Slave response timeout(ms) */ >>>>> + ? ? ? .sm ? ? ? ? ? ? = I2C_FREQ_MODE_FAST, >>>> >>>> How is this possible? you are setting clk_freq as 100kb/s and mode >>>> as fast mode which is supposed to be 400kb/s. >>> >>> That's not how I read it: >> >> >> But it is not readable. It confuses people. > > I understood it. :) > > If you think it's unclear speak to the author, Linus. He's CC'ed. Author of what? The i2c driver was written by Srinidhi. (The MODULE_AUTHOR() clause should be a good hint...) But it's true that board data for the ux500 kernel use 100000 Hz and I2C_FREQ_MODE_FAST, in the board-mop500.c file, like this: U8500_I2C_CONTROLLER(0, 0xe, 1, 8, 100000, 200, I2C_FREQ_MODE_FAST); U8500_I2C_CONTROLLER(1, 0xe, 1, 8, 100000, 200, I2C_FREQ_MODE_FAST); U8500_I2C_CONTROLLER(2, 0xe, 1, 8, 100000, 200, I2C_FREQ_MODE_FAST); U8500_I2C_CONTROLLER(3, 0xe, 1, 8, 100000, 200, I2C_FREQ_MODE_FAST); This is indeed a bit odd. But obviously it works... But reading some fixes in another tree it seems it should look like this: /* * The board uses 4 i2c controllers, initialize all of * them with slave data setup time of 250 ns, * Tx & Rx FIFO threshold values as 1 and standard * mode of operation */ U8500_I2C_CONTROLLER(0, 0xe, 1, 8, 400000, 200, I2C_FREQ_MODE_FAST); U8500_I2C_CONTROLLER(1, 0xe, 1, 8, 400000, 200, I2C_FREQ_MODE_FAST); U8500_I2C_CONTROLLER(2, 0xe, 1, 8, 400000, 200, I2C_FREQ_MODE_FAST); U8500_I2C_CONTROLLER(3, 0xe, 1, 8, 400000, 200, I2C_FREQ_MODE_FAST); Which makes *much* more sense. I'll cook a separate patch for this or something. Thanks, Linus Walleij -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/