Re: [PATCH 14/18] hwmon: add support for the sl28cpld hardware monitoring controller

[Michael Walle <michael@walle.cc>]

Hi Guenter,

thanks for the review

Am 2020-03-18 04:27, schrieb Guenter Roeck:
> On 3/17/20 1:50 PM, Michael Walle wrote:
>> This adds support for the hardware monitoring controller of the 
>> sl28cpld
>> board management controller. This driver is part of a multi-function
>> device.
>> 
>> Signed-off-by: Michael Walle <michael@walle.cc>
>> ---
>>  drivers/hwmon/Kconfig          |  10 +++
>>  drivers/hwmon/Makefile         |   1 +
>>  drivers/hwmon/sl28cpld-hwmon.c | 146 
>> +++++++++++++++++++++++++++++++++
> 
> Please also provide Documentation/hwmon/sl28cpld.
> 
>>  3 files changed, 157 insertions(+)
>>  create mode 100644 drivers/hwmon/sl28cpld-hwmon.c
>> 
>> diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
>> index 05a30832c6ba..c98716f78cfa 100644
>> --- a/drivers/hwmon/Kconfig
>> +++ b/drivers/hwmon/Kconfig
>> @@ -1412,6 +1412,16 @@ config SENSORS_RASPBERRYPI_HWMON
>>  	  This driver can also be built as a module. If so, the module
>>  	  will be called raspberrypi-hwmon.
>> 
>> +config SENSORS_SL28CPLD
>> +	tristate "Kontron's SMARC-sAL28 hardware monitoring driver"
>> +	depends on MFD_SL28CPLD
>> +	help
>> +	  If you say yes here you get support for a fan connected to the
>> +	  input of the SMARC connector of Kontron's SMARC-sAL28 module.
>> +
>> +	  This driver can also be built as a module.  If so, the module
>> +	  will be called sl28cpld-hwmon.
>> +
>>  config SENSORS_SHT15
>>  	tristate "Sensiron humidity and temperature sensors. SHT15 and 
>> compat."
>>  	depends on GPIOLIB || COMPILE_TEST
>> diff --git a/drivers/hwmon/Makefile b/drivers/hwmon/Makefile
>> index b0b9c8e57176..dfb0f8cda2dd 100644
>> --- a/drivers/hwmon/Makefile
>> +++ b/drivers/hwmon/Makefile
>> @@ -155,6 +155,7 @@ obj-$(CONFIG_SENSORS_S3C)	+= s3c-hwmon.o
>>  obj-$(CONFIG_SENSORS_SCH56XX_COMMON)+= sch56xx-common.o
>>  obj-$(CONFIG_SENSORS_SCH5627)	+= sch5627.o
>>  obj-$(CONFIG_SENSORS_SCH5636)	+= sch5636.o
>> +obj-$(CONFIG_SENSORS_SL28CPLD)	+= sl28cpld-hwmon.o
>>  obj-$(CONFIG_SENSORS_SHT15)	+= sht15.o
>>  obj-$(CONFIG_SENSORS_SHT21)	+= sht21.o
>>  obj-$(CONFIG_SENSORS_SHT3x)	+= sht3x.o
>> diff --git a/drivers/hwmon/sl28cpld-hwmon.c 
>> b/drivers/hwmon/sl28cpld-hwmon.c
>> new file mode 100644
>> index 000000000000..7ac42bb0a48c
>> --- /dev/null
>> +++ b/drivers/hwmon/sl28cpld-hwmon.c
>> @@ -0,0 +1,146 @@
>> +// SPDX-License-Identifier: GPL-2.0-only
>> +/*
>> + * SMARC-sAL28 fan hardware monitoring driver.
>> + *
>> + * Copyright 2019 Kontron Europe GmbH
>> + */
>> +
>> +#include <linux/kernel.h>
>> +#include <linux/module.h>
>> +#include <linux/bitfield.h>
>> +#include <linux/of.h>
>> +#include <linux/of_device.h>
>> +#include <linux/of_address.h>
>> +#include <linux/regmap.h>
>> +#include <linux/platform_device.h>
>> +#include <linux/hwmon.h>
>> +
> Alphabetic order of include files, please.

ok, I guess that applies to all of the new files.


>> +#define FAN_INPUT		0
>> +#define   FAN_SCALE_X8		BIT(7)
>> +#define   FAN_VALUE_MASK	GENMASK(6, 0)
>> +
>> +struct sl28cpld_hwmon {
>> +	struct regmap *regmap;
>> +	u32 offset;
>> +};
>> +
>> +static umode_t sl28cpld_hwmon_is_visible(const void *data,
>> +					 enum hwmon_sensor_types type,
>> +					 u32 attr, int channel)
>> +{
>> +	return 0444;
>> +}
>> +
>> +static int sl28cpld_hwmon_read(struct device *dev,
>> +			       enum hwmon_sensor_types type, u32 attr,
>> +			       int channel, long *input)
>> +{
>> +	struct sl28cpld_hwmon *hwmon = dev_get_drvdata(dev);
>> +	unsigned int value;
>> +	int ret;
>> +
>> +	switch (attr) {
>> +	case hwmon_fan_input:
>> +		ret = regmap_read(hwmon->regmap, hwmon->offset + FAN_INPUT,
>> +				  &value);
>> +		if (ret)
>> +			return ret;
>> +		/*
>> +		 * The register has a 7 bit value and 1 bit which indicates the
>> +		 * scale. If the MSB is set, then the lower 7 bit has to be
>> +		 * multiplied by 8, to get the correct reading.
>> +		 */
>> +		if (value & FAN_SCALE_X8)
>> +			value = FIELD_GET(FAN_VALUE_MASK, value) << 3;
>> +
>> +		/*
>> +		 * The counter period is 1000ms and the sysfs specification
>> +		 * says we should asssume 2 pulses per revolution.
>> +		 */
>> +		value *= 60 / 2;
>> +
>> +		break;
>> +	default:
>> +		return -EOPNOTSUPP;
>> +	}
>> +
>> +	*input = value;
>> +	return 0;
>> +}
>> +
>> +static const u32 sl28cpld_hwmon_fan_config[] = {
>> +	HWMON_F_INPUT,
>> +	0
>> +};
>> +
>> +static const struct hwmon_channel_info sl28cpld_hwmon_fan = {
>> +	.type = hwmon_fan,
>> +	.config = sl28cpld_hwmon_fan_config,
>> +};
>> +
>> +static const struct hwmon_channel_info *sl28cpld_hwmon_info[] = {
>> +	&sl28cpld_hwmon_fan,
>> +	NULL
>> +};
>> +
>> +static const struct hwmon_ops sl28cpld_hwmon_ops = {
>> +	.is_visible = sl28cpld_hwmon_is_visible,
>> +	.read = sl28cpld_hwmon_read,
>> +};
>> +
>> +static const struct hwmon_chip_info sl28cpld_hwmon_chip_info = {
>> +	.ops = &sl28cpld_hwmon_ops,
>> +	.info = sl28cpld_hwmon_info,
>> +};
>> +
>> +static int sl28cpld_hwmon_probe(struct platform_device *pdev)
>> +{
>> +	struct device *hwmon_dev;
>> +	struct sl28cpld_hwmon *hwmon;
>> +	struct resource *res;
>> +
>> +	hwmon = devm_kzalloc(&pdev->dev, sizeof(*hwmon), GFP_KERNEL);
>> +	if (!hwmon)
>> +		return -ENOMEM;
>> +
>> +	if (!pdev->dev.parent)
>> +		return -ENODEV;
>> +
> Maybe do this first ?

ok. like explained on another patch review comment, I had that
together with the following dev_get_regmap() which uses this.
But I was already not sure while writing the code whether I
should do it first and don't have to undo the devm_ in case of
an error. Well since already two reviewers stumbled on this,
I'll do it first on all the patches.


>> +	hwmon->regmap = dev_get_regmap(pdev->dev.parent, NULL);
>> +	if (!hwmon->regmap)
>> +		return -ENODEV;
>> +
>> +	res = platform_get_resource(pdev, IORESOURCE_REG, 0);
>> +	if (!res)
>> +		return -EINVAL;
>> +	hwmon->offset = res->start;
>> +
>> +	hwmon_dev = devm_hwmon_device_register_with_info(&pdev->dev,
>> +							 "sl28cpld_hwmon",
>> +							 hwmon,
>> +							 &sl28cpld_hwmon_chip_info,
>> +							 NULL);
>> +	if (IS_ERR(hwmon_dev)) {
>> +		dev_err(&pdev->dev, "failed to register as hwmon device");
>> +		return PTR_ERR(hwmon_dev);
>> +	}
>> +
>> +	return 0;
>> +}
>> +
>> +static const struct platform_device_id sl28cpld_hwmon_id_table[] = {
>> +	{"sl28cpld-fan", 0},
>> +};
>> +MODULE_DEVICE_TABLE(platform, sl28cpld_hwmon_id_table);
>> +
>> +static struct platform_driver sl28cpld_hwmon_driver = {
>> +	.probe = sl28cpld_hwmon_probe,
>> +	.id_table = sl28cpld_hwmon_id_table,
> 
> I'd have expected an of_match_table.

There was one, but, since I use mfd_add_devices() which uses the
platform driver name (or the id_table) I removed it. While it
doesn't really matter here in the hwmon part for now, the GPIO
driver uses the id_table data to distinguish between different
flavors of the GPIO controller. So there I'd have to duplicate
data in the tables (eg. the id_table as well as the
of_match_table) and get that data in the _probe(), although only
the id_table data is used.

-michael

> 
>> +	.driver = {
>> +		.name = "sl28cpld-hwmon",
>> +	},
>> +};
>> +module_platform_driver(sl28cpld_hwmon_driver);
>> +
>> +MODULE_DESCRIPTION("sl28cpld Hardware Monitoring Driver");
>> +MODULE_LICENSE("GPL");
>>