From mboxrd@z Thu Jan 1 00:00:00 1970 From: Guenter Roeck Subject: Re: [PATCH 1/2] hwmon: (lm90) Add power control Date: Wed, 07 Aug 2013 00:50:04 -0700 Message-ID: <5201FC2C.4030908@roeck-us.net> 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> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <5201F811.9050602-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org> Sender: linux-tegra-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Wei Ni Cc: Alexander Shiyan , "khali-PUYAD+kWke1g9hUCZPvPmw@public.gmane.org" , "swarren-3lzwWm7+Weoh9ZMKESR00Q@public.gmane.org" , "linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , "lm-sensors-GZX6beZjE8VD60Wz+7aTrA@public.gmane.org" , Matthew Longnecker , "linux-tegra-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , "linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org" List-Id: linux-tegra@vger.kernel.org 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