From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753110Ab2GILBf (ORCPT ); Mon, 9 Jul 2012 07:01:35 -0400 Received: from mail-pb0-f46.google.com ([209.85.160.46]:59365 "EHLO mail-pb0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752841Ab2GILBe (ORCPT ); Mon, 9 Jul 2012 07:01:34 -0400 Message-ID: <1341831686.4343.7.camel@phoenix> Subject: Re: [PATCH RFT 1/2] regulator: twl: Fix the formula to calculate vsel and voltage for twl6030ldo From: Axel Lin To: Mark Brown Cc: Rajendra Nayak , Peter Ujfalusi , Liam Girdwood , linux-kernel@vger.kernel.org Date: Mon, 09 Jul 2012 19:01:26 +0800 In-Reply-To: <1341804151.14367.1.camel@phoenix> References: <1341804151.14367.1.camel@phoenix> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.2.3-0ubuntu6 Content-Transfer-Encoding: 8bit Mime-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. > 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? Regards, Axel