From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751584Ab2GPJLQ (ORCPT ); Mon, 16 Jul 2012 05:11:16 -0400 Received: from na3sys009aog102.obsmtp.com ([74.125.149.69]:51432 "EHLO na3sys009aog102.obsmtp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751182Ab2GPJLN (ORCPT ); Mon, 16 Jul 2012 05:11:13 -0400 Message-ID: <5003DAAA.2070301@ti.com> Date: Mon, 16 Jul 2012 14:41:06 +0530 From: Rajendra Nayak User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.2.20) Gecko/20110805 Thunderbird/3.1.12 MIME-Version: 1.0 To: Axel Lin CC: Mark Brown , Peter Ujfalusi , Liam Girdwood , linux-kernel@vger.kernel.org, loml Subject: Re: [PATCH RFT 1/2] regulator: twl: Fix the formula to calculate vsel and voltage for twl6030ldo References: <1341804151.14367.1.camel@phoenix> <1341831686.4343.7.camel@phoenix> In-Reply-To: <1341831686.4343.7.camel@phoenix> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Axel, My apologies for the delay in responding to this one. On Monday 09 July 2012 04:31 PM, Axel Lin wrote: > 於 一，2012-07-09 於 11:22 +0800，Axel Lin 提到： >> In twl6030ldo_set_voltage, current code use below formula to calculate vsel: >> vsel = (min_uV/1000 - 1000)/100 + 1; >> This is worng because when min_uV is 1000000 uV, vsel is 1. >> It should be 0 in this case. Why? Do you know of any documentation which states this? I am referring to the twl6030 Top Functional spec version 1.18 and Table - 223 "LDO Output Voltage Selection Code" clearly states that the vsel should be 1 when voltage expected is 1000000 uV. Also refer to equation 3 "LDO Output Voltage Selection Code" in the same document and you will see this mentioned.. Absolute Voltage value = 1.0V + 0.1V * (binary value – 00000001) >> Fix it by change the equation to: (This equation is common for linear mapping) >> vsel = DIV_ROUND_UP(min_uV - rdev->desc->min_uV, rdev->desc->uV_step); >> >> In twl6030ldo_get_voltage, current code use below formula to calculate voltage: >> mV = 1000mv + 100mv * (vsel - 1) >> This is worng because when vsel is 0, mV is 900mV. Note the min_uV is 1000mV. >> Fix it by change the equation to: (This equation is common for linear mapping) >> return rdev->desc->min_uV + vsel * rdev->desc->uV_step; > > While I'm thinking I need to rework this patch so that it doesn't use > rdev->desc->min_uV and rdev->desc->uV_step and then can be applied > to current Linus' tree. > > But while I am tracking back to commit 3e3d3be79c > Author: Rajendra Nayak > Date: Thu Apr 22 14:18:32 2010 +0530 > > twl6030: regulator: Remove vsel tables and use formula for > calculation > > All twl6030 regulators can be programmed from 1.0v to 3.3v > with 100mV steps. > The below formula can be used to calculate the vsel values > to be programmed in the VREG_VOLTAGE registers. > > Voltage(in mV) = 1000mv + 100mv * (vsel - 1) > > Ex: if vsel = 0x9, mV = 1000 + 100 * (9 -1) = 1800mV. > > This patch removes all existing VSEL tables for twl6030 adjustable > regulators and just uses the formula directly for vsel calculations > after verifing they fall in the allowed range. > > Signed-off-by: Rajendra Nayak > > I found a problem that before commit 3e3d3be79c, the voltage tables were > not linear mapping. So why we can convert these voltage mapping table to > Voltage(in mV) = 1000mv + 100mv * (vsel - 1)? > > Did I miss something? All voltage tables before commit '3e3d3be79c' for twl6030 regulators were clearly wrong. They assumed similarity with twl4030 regulators which was not right. regards, Rajendra > > Regards, > Axel > >