Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932203Ab3HGHuB (ORCPT ); Wed, 7 Aug 2013 03:50:01 -0400 Received: from mail.active-venture.com ([67.228.131.205]:61171 "EHLO mail.active-venture.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756960Ab3HGHuA (ORCPT ); Wed, 7 Aug 2013 03:50:00 -0400 X-Originating-IP: 108.223.40.66 Message-ID: <5201FC2C.4030908@roeck-us.net> Date: Wed, 07 Aug 2013 00:50:04 -0700 From: Guenter Roeck User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130623 Thunderbird/17.0.7 MIME-Version: 1.0 To: Wei Ni CC: Alexander Shiyan , "khali@linux-fr.org" , "swarren@wwwdotorg.org" , "linux-kernel@vger.kernel.org" , "lm-sensors@lm-sensors.org" , Matthew Longnecker , "linux-tegra@vger.kernel.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> <1375858358-15070-2-git-send-email-wni@nvidia.com> <1375860442.896960598@f427.i.mail.ru> <5201F811.9050602@nvidia.com> In-Reply-To: <5201F811.9050602@nvidia.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1882 Lines: 50 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. Besides that, your delay is unconditional, even for static regulators which are always on. Other callers of regulator_enable() don't need all that complexity, which I take as sign that it is not needed here either. Guenter -- 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/