Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932370Ab3HGJfK (ORCPT ); Wed, 7 Aug 2013 05:35:10 -0400 Received: from hqemgate15.nvidia.com ([216.228.121.64]:15434 "EHLO hqemgate15.nvidia.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932296Ab3HGJfH (ORCPT ); Wed, 7 Aug 2013 05:35:07 -0400 X-PGP-Universal: processed; by hqnvupgp07.nvidia.com on Wed, 07 Aug 2013 02:35:06 -0700 Message-ID: <520214C9.1010200@nvidia.com> Date: Wed, 7 Aug 2013 17:35:05 +0800 From: Wei Ni User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130623 Thunderbird/17.0.7 MIME-Version: 1.0 To: Alexander Shiyan CC: Guenter Roeck , "swarren@wwwdotorg.org" , "linux-kernel@vger.kernel.org" , "lm-sensors@lm-sensors.org" , "linux-tegra@vger.kernel.org" , Matthew Longnecker , "khali@linux-fr.org" , "linux-arm-kernel@lists.infradead.org" Subject: Re: [PATCH 1/2] hwmon: (lm90) Add power control References: <1375858358-15070-1-git-send-email-wni@nvidia.com> <5201FC2C.4030908@roeck-us.net> <52020047.1080705@nvidia.com> <1375865105.562600640@f434.i.mail.ru> In-Reply-To: <1375865105.562600640@f434.i.mail.ru> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2526 Lines: 67 On 08/07/2013 04:45 PM, Alexander Shiyan wrote: >> On 08/07/2013 03:50 PM, Guenter Roeck wrote: >>> On 08/07/2013 12:32 AM, Wei Ni wrote: >>>> On 08/07/2013 03:27 PM, Alexander Shiyan wrote: >>>>>> The device lm90 can be controlled by the vdd rail. >>>>>> Adding the power control support to power on/off the vdd rail. >>>>>> And make sure that power is enabled before accessing the device. >>>>>> >>>>>> Signed-off-by: Wei Ni >>>>>> --- >>>>>> drivers/hwmon/lm90.c | 52 ++++++++++++++++++++++++++++++++++++++++++++++++++ >>>>> [...] >>>>>> + if (!data->lm90_reg) { >>>>>> + data->lm90_reg = regulator_get(&client->dev, "vdd"); >>>>>> + if (IS_ERR_OR_NULL(data->lm90_reg)) { >>>>>> + if (PTR_ERR(data->lm90_reg) == -ENODEV) >>>>>> + dev_info(&client->dev, >>>>>> + "No regulator found for vdd. Assuming vdd is always powered."); >>>>>> + else >>>>>> + dev_warn(&client->dev, >>>>>> + "Error [%ld] in getting the regulator handle for vdd.\n", >>>>>> + PTR_ERR(data->lm90_reg)); >>>>>> + data->lm90_reg = NULL; >>>>>> + mutex_unlock(&data->update_lock); >>>>>> + return -ENODEV; >>>>>> + } >>>>>> + } >>>>>> + if (is_enable) { >>>>>> + ret = regulator_enable(data->lm90_reg); >>>>>> + msleep(POWER_ON_DELAY); >>>>> >>>>> Can this delay be handled directly from regulator? >>>> >>>> I think it should be handled in the device driver. >>>> Because there have different delay time to wait devices stable. >>>> >>> >>> Then why does no other caller of regulator_enable() need this ? >>> I don't think lm90 is so much different to other users of regulator >>> functionality. >> >> May be I'm wrong. I noticed that in lm90 SPEC, the max of "SMBus Clock >> Low Time" is 25ms, so I supposed that it may need about 20ms to stable >> after power on. >> >> Anyway, if I remove this delay, the driver also works fine, so I will >> remove it in my next patch. > > I originally had in mind that regulator API contain own delay option. > E.g. reg-fixed-voltage && gpio-regulator contains "startup-delay-us" property. As I know the "startup-delay-us" is used for the regulator device, not the consumer devices. In this patch, msleep(POWER_ON_DELAY) was used to wait the lm90 stable, but it seems it's unnecessary now :) Wei. > > --- > -- 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/