On 02/20/2018 11:15 PM, Mikko Perttunen wrote:
AIUI, the PWM framework already exposes a sysfs node with period information. We should just use that instead of adding a new driver for this.
I am kind of lost. Please explain. Are you saying that we should drop the pwm-fan driver as well (which goes the opposite way), as well as any other drivers doing anything with pwm signals, because after all those signals are already exposed to userspace a sysfs attributes, and a kernel driver to abstract those values is thus not needed ?
In any case, we cannot add something like this to device tree since it's not a hardware device.
So you are saying there is no means to express in devicetree that a pwm input is connected to a fan ? How is that not hardware ? If so, how do you express in devicetree that a pwm signal is connected to anything ? Guenter
Mikko On 21.02.2018 08:58, 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@xxxxxxxxxx> --- 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@xxxxxxxxxx> + +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, +}; + +ATTRIBUTE_GROUPS(pwm_tach); + +static int pwm_tach_probe(struct platform_device *pdev) +{ + struct pwm_hwmon_tach *ptt; + int err; + + ptt = devm_kzalloc(&pdev->dev, sizeof(*ptt), GFP_KERNEL); + if (!ptt) + return -ENOMEM; + + ptt->dev = &pdev->dev; + + platform_set_drvdata(pdev, ptt); + dev_set_drvdata(&pdev->dev, ptt); + + ptt->pwm = devm_of_pwm_get(&pdev->dev, pdev->dev.of_node, NULL); + if (IS_ERR(ptt->pwm)) { + err = PTR_ERR(ptt->pwm); + dev_err(&pdev->dev, "Failed to get pwm handle, err: %d\n", + err); + return err; + } + + ptt->hwmon = devm_hwmon_device_register_with_groups(&pdev->dev, + "pwm_tach", ptt, pwm_tach_groups); + if (IS_ERR(ptt->hwmon)) { + err = PTR_ERR_OR_ZERO(ptt->hwmon); + dev_err(&pdev->dev, "Failed to register hwmon device: %d\n", + err); + return err; + } + + return 0; +} + +static const struct of_device_id pwm_tach_of_match[] = { + { .compatible = "generic-pwm-tachometer" }, + {} +}; +MODULE_DEVICE_TABLE(of, pwm_tach_of_match); + +static struct platform_driver pwm_tach_driver = { + .driver = { + .name = "generic-pwm-tachometer", + .of_match_table = pwm_tach_of_match, + }, + .probe = pwm_tach_probe, +}; + +module_platform_driver(pwm_tach_driver); + +MODULE_DESCRIPTION("PWM based Generic Tachometer driver"); +MODULE_AUTHOR("Laxman Dewangan <ldewangan@xxxxxxxxxx>"); +MODULE_AUTHOR("Rajkumar Rampelli <rrajk@xxxxxxxxxx>"); +MODULE_LICENSE("GPL v2");
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