From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Google-Smtp-Source: AG47ELtJNYQzuPTlqbP3M0xG8yuhiruUxF8x0in8E93uCAnr25hVkuXxt10L68ct+NAfUaZhEytw ARC-Seal: i=1; a=rsa-sha256; t=1520495851; cv=none; d=google.com; s=arc-20160816; b=BczBTz1l0i0LlHtD2JBoGJ9V0rxkLFH0AH9577oHVn+5fHsukxBxAI/06orS1/OF/U 0VdKJjvoI3Y4c7SSY/alu7Rw6i8DFce06rQJl59f0+shXfMNM9AIyuYIQ8EhKYo3kPx2 8cBhB7TKrvsC42rJXj7Lf0bRF00isf+y8voXBgOFzKsiMjMQ7y/VPWqzX3T4s5icqN8x 1Hyvntl/Q58Cit4Zt9qCfDcihe+bO5b2BlufRZMr3U5+PTgn8+xv6uQoB4/lEY+3qjhx QQbI/TByl5vpQkbiP3KzL55hogoQcQc743pqfdlCiKV/tk9r8jt6brVVZtbTwKoy53rQ lwWw== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=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=Q4d8MmI2a3cFtORml9FqkVu2Jf7uT0xb2YR9gW0zJciBSJ4YjUcMVLfjnZvaFpM8wE 9B8LA2Musikf3ZJtQCXzKP4vcouCnvys7j08m/weOZ8PYwIoWQ+7931seAC9qeqwrSYj qYFfBS6nBkg7Vknf5Lji8XCb/XLf3EfjSbsPnctu8MB/ULB1QzHR8yyZ9WZuE9yrITBr w2fZdAJ8uQ+37/84Z3GP5xG68HdB5lZe/O3+Xz38KDPCdTHPrQfHuvLRMKvIHGy3A7TA +DLPw8NKy7+OL98Kbvuo6J9JYvD1G1jDK95ikziFV9QmB4vvX7m7dkM7eRN7HYs5HmK/ kQ7A== ARC-Authentication-Results: i=1; mx.google.com; spf=pass (google.com: domain of mperttunen@nvidia.com designates 216.228.121.65 as permitted sender) smtp.mailfrom=mperttunen@nvidia.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=nvidia.com Authentication-Results: mx.google.com; spf=pass (google.com: domain of mperttunen@nvidia.com designates 216.228.121.65 as permitted sender) smtp.mailfrom=mperttunen@nvidia.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=nvidia.com X-PGP-Universal: processed; by hqpgpgate101.nvidia.com on Wed, 07 Mar 2018 23:57:30 -0800 Subject: Re: [PATCH 05/10] hwmon: generic-pwm-tachometer: Add generic PWM based tachometer To: Guenter Roeck , Rajkumar Rampelli , Mikko Perttunen , , , , , , , , , , , , , , , , , , , , 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> <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> CC: , , , , , , , From: Mikko Perttunen 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: 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 X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: =?utf-8?q?1592992898629636853?= X-GMAIL-MSGID: =?utf-8?q?1594355458133736886?= X-Mailing-List: linux-kernel@vger.kernel.org List-ID: 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 >>>>>>>>> --- >>>>>>>>> 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 >>>>>>>>> + >>>>>>>>> +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 >>>>>>>>> +#include >>>>>>>>> +#include >>>>>>>>> +#include >>>>>>>>> +#include >>>>>>>>> +#include >>>>>>>>> + >>>>>>>>> +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 >>>> >>> >> >> >