Received: by 10.223.185.116 with SMTP id b49csp6018494wrg;
        Wed, 7 Mar 2018 23:58:49 -0800 (PST)
X-Google-Smtp-Source: AG47ELtBxSNYSia19guezv6ZiqjU/of+YBrzceyRwp9oyX6Wkcm1MNr0K0yuhuPdF5IqqdbZkb9J
X-Received: by 10.101.65.131 with SMTP id a3mr20076951pgq.270.1520495929196;
        Wed, 07 Mar 2018 23:58:49 -0800 (PST)
ARC-Seal: i=1; a=rsa-sha256; t=1520495929; cv=none;
        d=google.com; s=arc-20160816;
        b=ilXqxKOakdSo53euorZZmjx3w3cwXxtyf/K3+HCaxzytLP/H3n5A5AVqPdI1zcf1Yt
         xLekGoIiTYZAIUribmG/4qpY/oQvzTy0zcOzkB0FSJpc2pvKe91jas1oCMZTtqRisrSY
         w/8VMJEDxkYbcp2wd8nHgWFvVPk9Xc+VVPfjfrRGgWMzJNya1bu99/XRlkyFLnkpaQ2Y
         dtHNBvt7B0eBMrB5u6Xo8mIlUVk/nZmgRnc4X9DGBoTHF5TFEyE1sh+bPRGdQbB2y/YB
         HC0zMO4cf2qwbI8ITP62zQ04++Wlt9b96p9X4XZsekP02AY7MjRRyEu7qTqhZu9j/BuW
         AqEA==
ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816;
        h=list-id:precedence:sender:content-transfer-encoding:in-reply-to
         :mime-version:user-agent:date:message-id:from:cc:references:to
         :subject:arc-authentication-results;
        bh=ly5y3r/jmc5hwHrL4rHEqAZwWa526h/GsOyxNISS++c=;
        b=wxhsGdjVBAEhqzgIyXK2bSowaekR9biUsX7DkZAcLGqExF0vP/IzgvJcSsd4WH4j4+
         MKzBGSrq8USDRtqyiAY7ifEpVjHcXrQoJKBrzgj3dDwefeR4i9DxJDdGauBFlsYOgLe5
         6dyZ6J2RDnis5kPy3nUsrOLvOFMlSQfacmpGsbWoKHdNxrx+wBxKiMMH+jWp5fpZ7507
         t4w/CpMVxMwXeVa3eCcD+FBHrner4u89nietrTVnKencwDanNjXn6YolBrbtJxITtnHO
         1tIGCgbJk09l3yabuuXSZrpDPHmPzySe5U7vNEdZcCArZwle1HCXNZKHTEBKFcitDRX+
         6KCA==
ARC-Authentication-Results: i=1; mx.google.com;
       spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org;
       dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=nvidia.com
Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: from vger.kernel.org (vger.kernel.org. [209.132.180.67])
        by mx.google.com with ESMTP id a25si12568593pgn.429.2018.03.07.23.58.34;
        Wed, 07 Mar 2018 23:58:49 -0800 (PST)
Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Authentication-Results: mx.google.com;
       spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org;
       dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=nvidia.com
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
        id S1755154AbeCHH5e (ORCPT <rfc822;ttoukan.linux@gmail.com>
        + 99 others); Thu, 8 Mar 2018 02:57:34 -0500
Received: from hqemgate16.nvidia.com ([216.228.121.65]:11037 "EHLO
        hqemgate16.nvidia.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
        with ESMTP id S1751603AbeCHH5b (ORCPT
        <rfc822;linux-kernel@vger.kernel.org>);
        Thu, 8 Mar 2018 02:57:31 -0500
Received: from hqpgpgate101.nvidia.com (Not Verified[216.228.121.13]) by hqemgate16.nvidia.com
        id <B5aa0ece90000>; Wed, 07 Mar 2018 23:57:29 -0800
Received: from HQMAIL106.nvidia.com ([172.20.161.6])
  by hqpgpgate101.nvidia.com (PGP Universal service);
  Wed, 07 Mar 2018 23:57:30 -0800
X-PGP-Universal: processed;
        by hqpgpgate101.nvidia.com on Wed, 07 Mar 2018 23:57:30 -0800
Received: from UKMAIL101.nvidia.com (10.26.138.13) by HQMAIL106.nvidia.com
 (172.18.146.12) with Microsoft SMTP Server (TLS) id 15.0.1347.2; Thu, 8 Mar
 2018 07:57:29 +0000
Received: from [10.21.26.144] (10.21.26.144) by UKMAIL101.nvidia.com
 (10.26.138.13) with Microsoft SMTP Server (TLS) id 15.0.1347.2; Thu, 8 Mar
 2018 07:57:23 +0000
Subject: Re: [PATCH 05/10] hwmon: generic-pwm-tachometer: Add generic PWM
 based tachometer
To:     Guenter Roeck <linux@roeck-us.net>,
        Rajkumar Rampelli <rrajk@nvidia.com>,
        Mikko Perttunen <cyndis@kapsi.fi>, <robh+dt@kernel.org>,
        <mark.rutland@arm.com>, <thierry.reding@gmail.com>,
        <jonathanh@nvidia.com>, <jdelvare@suse.com>, <corbet@lwn.net>,
        <catalin.marinas@arm.com>, <will.deacon@arm.com>,
        <kstewart@linuxfoundation.org>, <gregkh@linuxfoundation.org>,
        <pombredanne@nexb.com>, <mmaddireddy@nvidia.com>, <arnd@arndb.de>,
        <timur@codeaurora.org>, <andy.gross@linaro.org>,
        <xuwei5@hisilicon.com>, <elder@linaro.org>, <heiko@sntech.de>,
        <krzk@kernel.org>, <ard.biesheuvel@linaro.org>
References: <1519196339-9377-1-git-send-email-rrajk@nvidia.com>
 <1519196339-9377-6-git-send-email-rrajk@nvidia.com>
 <5172edff-fe29-7ed1-f0d2-b0359ea2c24d@roeck-us.net>
 <2510b525-ec36-b49d-5a62-81f335c0d10d@nvidia.com>
 <cfe0d0ce-3a89-bad0-85ba-6edf1135d2dc@roeck-us.net>
 <2628eff2-dd33-34f4-a7e1-cfe46ef88a3f@nvidia.com>
 <4556a8d2-947d-72c4-2962-3167afb53978@kapsi.fi>
 <62ba7f67-5a99-51ab-1214-eb68ebb7e642@roeck-us.net>
 <952cb50e-d9a0-ae5e-d9f6-d1ce268f0384@nvidia.com>
 <f7818e4c-17b6-c58b-3424-85749bb9c1cc@roeck-us.net>
CC:     <devicetree@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
        <linux-pwm@vger.kernel.org>, <linux-tegra@vger.kernel.org>,
        <linux-hwmon@vger.kernel.org>, <linux-doc@vger.kernel.org>,
        <linux-arm-kernel@lists.infradead.org>, <ldewangan@nvidia.com>
From:   Mikko Perttunen <mperttunen@nvidia.com>
Message-ID: <73ca5840-865b-b44e-45e6-703b7749fb6f@nvidia.com>
Date:   Thu, 8 Mar 2018 09:57:22 +0200
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101
 Thunderbird/45.2.0
MIME-Version: 1.0
In-Reply-To: <f7818e4c-17b6-c58b-3424-85749bb9c1cc@roeck-us.net>
X-Originating-IP: [10.21.26.144]
X-ClientProxiedBy: UKMAIL102.nvidia.com (10.26.138.15) To UKMAIL101.nvidia.com
 (10.26.138.13)
Content-Type: text/plain; charset="utf-8"; format=flowed
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org



On 07.03.2018 16:20, Guenter Roeck wrote:
> On 03/07/2018 01:47 AM, Rajkumar Rampelli wrote:
>>
>>
>> On Wednesday 28 February 2018 07:59 PM, Guenter Roeck wrote:
>>> On 02/27/2018 11:03 PM, Mikko Perttunen wrote:
>>>> On 02/28/2018 08:12 AM, Rajkumar Rampelli wrote:
>>>>>
>>>>> On Wednesday 28 February 2018 11:28 AM, Guenter Roeck wrote:
>>>>>> On 02/27/2018 09:38 PM, Rajkumar Rampelli wrote:
>>>>>>>
>>>>>>> On Wednesday 21 February 2018 08:20 PM, Guenter Roeck wrote:
>>>>>>>> On 02/20/2018 10:58 PM, Rajkumar Rampelli wrote:
>>>>>>>>> Add generic PWM based tachometer driver via HWMON interface
>>>>>>>>> to report the RPM of motor. This drivers get the period/duty
>>>>>>>>> cycle from PWM IP which captures the motor PWM output.
>>>>>>>>>
>>>>>>>>> This driver implements a simple interface for monitoring the
>>>>>>>>> speed of
>>>>>>>>> a fan and exposes it in roatations per minute (RPM) to the user
>>>>>>>>> space
>>>>>>>>> by using the hwmon's sysfs interface
>>>>>>>>>
>>>>>>>>> Signed-off-by: Rajkumar Rampelli <rrajk@nvidia.com>
>>>>>>>>> ---
>>>>>>>>>   Documentation/hwmon/generic-pwm-tachometer |  17 +++++
>>>>>>>>>   drivers/hwmon/Kconfig                      |  10 +++
>>>>>>>>>   drivers/hwmon/Makefile                     |   1 +
>>>>>>>>>   drivers/hwmon/generic-pwm-tachometer.c     | 112
>>>>>>>>> +++++++++++++++++++++++++++++
>>>>>>>>>   4 files changed, 140 insertions(+)
>>>>>>>>>   create mode 100644 Documentation/hwmon/generic-pwm-tachometer
>>>>>>>>>   create mode 100644 drivers/hwmon/generic-pwm-tachometer.c
>>>>>>>>>
>>>>>>>>> diff --git a/Documentation/hwmon/generic-pwm-tachometer
>>>>>>>>> b/Documentation/hwmon/generic-pwm-tachometer
>>>>>>>>> new file mode 100644
>>>>>>>>> index 0000000..e0713ee
>>>>>>>>> --- /dev/null
>>>>>>>>> +++ b/Documentation/hwmon/generic-pwm-tachometer
>>>>>>>>> @@ -0,0 +1,17 @@
>>>>>>>>> +Kernel driver generic-pwm-tachometer
>>>>>>>>> +====================================
>>>>>>>>> +
>>>>>>>>> +This driver enables the use of a PWM module to monitor a fan.
>>>>>>>>> It uses the
>>>>>>>>> +generic PWM interface and can be used on SoCs as along as the
>>>>>>>>> SoC supports
>>>>>>>>> +Tachometer controller that moniors the Fan speed in periods.
>>>>>>>>> +
>>>>>>>>> +Author: Rajkumar Rampelli <rrajk@nvidia.com>
>>>>>>>>> +
>>>>>>>>> +Description
>>>>>>>>> +-----------
>>>>>>>>> +
>>>>>>>>> +The driver implements a simple interface for monitoring the
>>>>>>>>> Fan speed using
>>>>>>>>> +PWM module and Tachometer controller. It requests period value
>>>>>>>>> through PWM
>>>>>>>>> +capture interface to Tachometer and measures the Rotations per
>>>>>>>>> minute using
>>>>>>>>> +received period value. It exposes the Fan speed in RPM to the
>>>>>>>>> user space by
>>>>>>>>> +using the hwmon's sysfs interface.
>>>>>>>>> diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
>>>>>>>>> index ef23553..8912dcb 100644
>>>>>>>>> --- a/drivers/hwmon/Kconfig
>>>>>>>>> +++ b/drivers/hwmon/Kconfig
>>>>>>>>> @@ -1878,6 +1878,16 @@ config SENSORS_XGENE
>>>>>>>>>         If you say yes here you get support for the temperature
>>>>>>>>>         and power sensors for APM X-Gene SoC.
>>>>>>>>>   +config GENERIC_PWM_TACHOMETER
>>>>>>>>> +    tristate "Generic PWM based tachometer driver"
>>>>>>>>> +    depends on PWM
>>>>>>>>> +    help
>>>>>>>>> +      Enables a driver to use PWM signal from motor to use
>>>>>>>>> +      for measuring the motor speed. The RPM is captured by
>>>>>>>>> +      PWM modules which has PWM capture capability and this
>>>>>>>>> +      drivers reads the captured data from PWM IP to convert
>>>>>>>>> +      it to speed in RPM.
>>>>>>>>> +
>>>>>>>>>   if ACPI
>>>>>>>>>     comment "ACPI drivers"
>>>>>>>>> diff --git a/drivers/hwmon/Makefile b/drivers/hwmon/Makefile
>>>>>>>>> index f814b4a..9dcc374 100644
>>>>>>>>> --- a/drivers/hwmon/Makefile
>>>>>>>>> +++ b/drivers/hwmon/Makefile
>>>>>>>>> @@ -175,6 +175,7 @@ obj-$(CONFIG_SENSORS_WM8350)    +=
>>>>>>>>> wm8350-hwmon.o
>>>>>>>>>   obj-$(CONFIG_SENSORS_XGENE)    += xgene-hwmon.o
>>>>>>>>>     obj-$(CONFIG_PMBUS)        += pmbus/
>>>>>>>>> +obj-$(CONFIG_GENERIC_PWM_TACHOMETER) += generic-pwm-tachometer.o
>>>>>>>>>     ccflags-$(CONFIG_HWMON_DEBUG_CHIP) := -DDEBUG
>>>>>>>>>   diff --git a/drivers/hwmon/generic-pwm-tachometer.c
>>>>>>>>> b/drivers/hwmon/generic-pwm-tachometer.c
>>>>>>>>> new file mode 100644
>>>>>>>>> index 0000000..9354d43
>>>>>>>>> --- /dev/null
>>>>>>>>> +++ b/drivers/hwmon/generic-pwm-tachometer.c
>>>>>>>>> @@ -0,0 +1,112 @@
>>>>>>>>> +/*
>>>>>>>>> + * Copyright (c) 2017-2018, NVIDIA CORPORATION.  All rights
>>>>>>>>> reserved.
>>>>>>>>> + *
>>>>>>>>> + * This program is free software; you can redistribute it
>>>>>>>>> and/or modify it
>>>>>>>>> + * under the terms and conditions of the GNU General Public
>>>>>>>>> License,
>>>>>>>>> + * version 2, as published by the Free Software Foundation.
>>>>>>>>> + *
>>>>>>>>> + * This program is distributed in the hope it will be useful,
>>>>>>>>> but WITHOUT
>>>>>>>>> + * ANY WARRANTY; without even the implied warranty of
>>>>>>>>> MERCHANTABILITY or
>>>>>>>>> + * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General
>>>>>>>>> Public License for
>>>>>>>>> + * more details.
>>>>>>>>> + *
>>>>>>>>> + */
>>>>>>>>> +
>>>>>>>>> +#include <linux/module.h>
>>>>>>>>> +#include <linux/platform_device.h>
>>>>>>>>> +#include <linux/err.h>
>>>>>>>>> +#include <linux/pwm.h>
>>>>>>>>> +#include <linux/hwmon.h>
>>>>>>>>> +#include <linux/hwmon-sysfs.h>
>>>>>>>>> +
>>>>>>>>> +struct pwm_hwmon_tach {
>>>>>>>>> +    struct device        *dev;
>>>>>>>>> +    struct pwm_device    *pwm;
>>>>>>>>> +    struct device        *hwmon;
>>>>>>>>> +};
>>>>>>>>> +
>>>>>>>>> +static ssize_t show_rpm(struct device *dev, struct
>>>>>>>>> device_attribute *attr,
>>>>>>>>> +            char *buf)
>>>>>>>>> +{
>>>>>>>>> +    struct pwm_hwmon_tach *ptt = dev_get_drvdata(dev);
>>>>>>>>> +    struct pwm_device *pwm = ptt->pwm;
>>>>>>>>> +    struct pwm_capture result;
>>>>>>>>> +    int err;
>>>>>>>>> +    unsigned int rpm = 0;
>>>>>>>>> +
>>>>>>>>> +    err = pwm_capture(pwm, &result, 0);
>>>>>>>>> +    if (err < 0) {
>>>>>>>>> +        dev_err(ptt->dev, "Failed to capture PWM: %d\n", err);
>>>>>>>>> +        return err;
>>>>>>>>> +    }
>>>>>>>>> +
>>>>>>>>> +    if (result.period)
>>>>>>>>> +        rpm = DIV_ROUND_CLOSEST_ULL(60ULL * NSEC_PER_SEC,
>>>>>>>>> +                        result.period);
>>>>>>>>> +
>>>>>>>>> +    return sprintf(buf, "%u\n", rpm);
>>>>>>>>> +}
>>>>>>>>> +
>>>>>>>>> +static SENSOR_DEVICE_ATTR(rpm, 0444, show_rpm, NULL, 0);
>>>>>>>>> +
>>>>>>>>> +static struct attribute *pwm_tach_attrs[] = {
>>>>>>>>> +    &sensor_dev_attr_rpm.dev_attr.attr,
>>>>>>>>> +    NULL,
>>>>>>>>> +};
>>>>>>>>
>>>>>>>> "rpm" is not a standard hwmon sysfs attribute. If you don't provide
>>>>>>>> a single standard hwmon sysfs attribute, having a hwmon driver
>>>>>>>> is pointless.
>>>>>>> Guenter Roeck,
>>>>>>> I will define a new hwmon sysfs attribute node called
>>>>>>> "hwmon_tachometer_attributes" in hwmon.h like below and update
>>>>>>> the same in tachometer hwmon driver. Is it fine ?
>>>>>>> enum hwmon_tachometer_attributes {
>>>>>>
>>>>>> Are you kidding me ?
>>>>>>
>>>>>> Guenter
>>>>> Sorry, I just wanted to confirm whether my understanding is correct
>>>>> or not before implementing it actually.
>>>>> Or, shall I add this attribute as a part of fan attributes with
>>>>> "hwmon_fan_rpm" ? or any other way to do it ? I need your inputs in
>>>>> fixing this.
>>>>
>>>> I think he wants the attribute to be named according to the
>>>> properties in this document:
>>>> https://www.kernel.org/doc/Documentation/hwmon/sysfs-interface. I
>>>> guess the attribute would then map to fan1_input, though I'm not
>>>> sure if that's 100% correct either since this could technically be
>>>> attached to something other than a fan. But I would think in
>>>> practice that's not a big concern.
>>>>
>>>> Guenter,
>>>> Please correct me as well if I'm wrong.
>>>>
>>> You are absolutely correct.
>>>
>>> While I am not opposed to ABI changes, the merits of those would need
>>> to be
>>> discussed on the mailing list. But replacing "fan1_input" with "rpm" is
>>> not an acceptable ABI change, even if it may measure something that
>>> turns
>>> but isn't a fan.
>>>
>>> If this _is_ in fact supposed to be used for something else but fans, we
>>> would have to discuss what that might be, and if hwmon is the
>>> appropriate
>>> subsystem to measure and report it. This does to some degree lead
>>> back to
>>> my concern of having the "fan" part of this patch series in the pwm
>>> core.
>>> I am still not sure if that makes sense.
>>>
>>> Thanks,
>>> Guenter
>> I am planning to add tachometer support in pwm-fan.c driver
>> (drivers/hwmon/) instead of adding new generic-pwm-tachometer.c
>> driver. Measuring RPM value will be done in pwm-fan driver itself
>> using pwm capture feature and will add new sysfs attributes under this
>> driver to report rpm value of fan.
>
> There is an existing attribute to report the RPM of fans. It is called
> fan[1..n]_input.
>
> "replacing "fan1_input" with "rpm" is not an acceptable ABI change"
>
> Preemptive NACK.
>
> Guenter
>

I think the idea here (based on personal discussion with Rajkumar) was 
to add a "new" sysfs attribute the driver exports, but that attribute 
would be the existing fan[1..n]_input.

Mikko

>>>
>>>> Thank you,
>>>> Mikko
>>>>
>>>>>
>>>>> --
>>>>> To unsubscribe from this list: send the line "unsubscribe
>>>>> linux-tegra" in
>>>>> the body of a message to majordomo@vger.kernel.org
>>>>> More majordomo info at http://vger.kernel.org/majordomo-info.html
>>>> --
>>>> To unsubscribe from this list: send the line "unsubscribe
>>>> linux-hwmon" in
>>>> the body of a message to majordomo@vger.kernel.org
>>>> More majordomo info at http://vger.kernel.org/majordomo-info.html
>>>>
>>>
>>
>>
>