Messages in this thread | | | Subject | Re: [PATCH 05/10] hwmon: generic-pwm-tachometer: Add generic PWM based tachometer | From | Guenter Roeck <> | Date | Wed, 21 Feb 2018 06:50:47 -0800 |
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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.
> + > +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); > +
None of those is used.
> + 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);
Please use the new API - devm_hwmon_device_register_with_info - for new drivers.
> + 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; > + }
Please no noise on failure. The failure is going to be a memory allocation failure, which is reported already, and user space will be informed with the error code.
> + > + 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@nvidia.com>"); > +MODULE_AUTHOR("Rajkumar Rampelli <rrajk@nvidia.com>"); > +MODULE_LICENSE("GPL v2"); >
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