Message-ID: <20170830005816.GA15324@roeck-us.net>
Date:   Tue, 29 Aug 2017 17:58:16 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Florian Eckert <fe@....tdt.de>
Cc:     jdelvare@...e.com, linux-hwmon@...r.kernel.org,
        linux-kernel@...r.kernel.org, dev@...sin.me
Subject: Re: [v2,1/2] hwmon: (ltq-cputemp) add cpu temp sensor driver

On Mon, Aug 21, 2017 at 02:41:22PM +0200, Florian Eckert wrote:
> Add the lantiq cpu temperature sensor support for xrx200.
> 
> Signed-off-by: Florian Eckert <fe@....tdt.de>
> ---
> v2:
> - remove default in Makefile
> - fix spelling
> - removing first read delay, because temperature value is not read during boot
>   anymore
> - change calculation, compiler should to the optimization
> - remove unnecessary initialization
> - use new devm_hwmon_device_register_with_info API
> - use module_platform_driver function
> 
> The soc detection for lantiq is done with this pattern. If it sould be more
> generic we should change this global.
> 
>  drivers/hwmon/Kconfig       |   7 ++
>  drivers/hwmon/Makefile      |   1 +
>  drivers/hwmon/ltq-cputemp.c | 175 ++++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 183 insertions(+)
>  create mode 100644 drivers/hwmon/ltq-cputemp.c
> 
> diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
> index 5ef2814345ef..218332f0e913 100644
> --- a/drivers/hwmon/Kconfig
> +++ b/drivers/hwmon/Kconfig
> @@ -790,6 +790,13 @@ config SENSORS_LTC4261
>  	  This driver can also be built as a module. If so, the module will
>  	  be called ltc4261.
>  
> +config SENSORS_LTQ_CPUTEMP
> +	bool "Lantiq cpu temperature sensor driver"
> +	depends on LANTIQ
> +	help
> +	  If you say yes here you get support for the temperature
> +	  sensor inside your CPU.
> +
>  config SENSORS_MAX1111
>  	tristate "Maxim MAX1111 Serial 8-bit ADC chip and compatibles"
>  	depends on SPI_MASTER
> diff --git a/drivers/hwmon/Makefile b/drivers/hwmon/Makefile
> index d4641a9f16c1..c84d9784be98 100644
> --- a/drivers/hwmon/Makefile
> +++ b/drivers/hwmon/Makefile
> @@ -110,6 +110,7 @@ obj-$(CONFIG_SENSORS_LTC4222)	+= ltc4222.o
>  obj-$(CONFIG_SENSORS_LTC4245)	+= ltc4245.o
>  obj-$(CONFIG_SENSORS_LTC4260)	+= ltc4260.o
>  obj-$(CONFIG_SENSORS_LTC4261)	+= ltc4261.o
> +obj-$(CONFIG_SENSORS_LTQ_CPUTEMP) += ltq-cputemp.o
>  obj-$(CONFIG_SENSORS_MAX1111)	+= max1111.o
>  obj-$(CONFIG_SENSORS_MAX16065)	+= max16065.o
>  obj-$(CONFIG_SENSORS_MAX1619)	+= max1619.o
> diff --git a/drivers/hwmon/ltq-cputemp.c b/drivers/hwmon/ltq-cputemp.c
> new file mode 100644
> index 000000000000..21c77a125c27
> --- /dev/null
> +++ b/drivers/hwmon/ltq-cputemp.c
> @@ -0,0 +1,175 @@
> +/* Lantiq cpu temperature sensor driver
> + *
> + * Copyright (C) 2017 Florian Eckert <fe@....tdt.de>
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License as published by
> + * the Free Software Foundation; either version 2 of the License, or
> + * (at your option) any later version
> + *
> + * This program is distributed in the hope that 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
> + *
> + * You should have received a copy of the GNU General Public License
> + * along with this program; if not, see <http://www.gnu.org/licenses/>
> + */
> +
> +#include <linux/module.h>
> +#include <linux/init.h>
> +#include <linux/delay.h>
> +#include <linux/of_device.h>
> +#include <linux/hwmon.h>
> +#include <linux/hwmon-sysfs.h>

Alphabetic order, please.

> +
> +#include <lantiq_soc.h>
> +
> +/* gphy1 configuration register contains cpu temperature */
> +#define CGU_GPHY1_CR   0x0040
> +#define CGU_TEMP_PD    BIT(19)

Requires include of linux/bitops.h.

> +
> +static void ltq_cputemp_enable(void)
> +{
> +	ltq_cgu_w32(ltq_cgu_r32(CGU_GPHY1_CR) | CGU_TEMP_PD, CGU_GPHY1_CR);
> +}
> +
> +static void ltq_cputemp_disable(void)
> +{
> +	ltq_cgu_w32(ltq_cgu_r32(CGU_GPHY1_CR) & ~CGU_TEMP_PD, CGU_GPHY1_CR);
> +}
> +
> +static int ltq_read(struct device *dev, enum hwmon_sensor_types type,
> +			u32 attr, int channel, long *temp)

alignment

> +{
> +	int value;
> +
> +	switch (attr) {
> +	case hwmon_temp_input:
> +		/* get the temperature including one decimal place */
> +		value = (ltq_cgu_r32(CGU_GPHY1_CR) >> 9) & 0x01FF;
> +		value = value * 5;
> +		/* range -38 to +154 °C, register value zero is -38.0 °C */
> +		value -= 380;
> +		/* scale temp to millidegree */
> +		value = value * 100;
> +	break;

indentation

> +	default:
> +		return -EOPNOTSUPP;
> +	}
> +
> +	*temp = value;
> +	return 0;
> +}
> +
> +
> +static umode_t ltq_is_visible(const void *_data, enum hwmon_sensor_types type,
> +				u32 attr, int channel)

Please align with '('.

> +{
> +	if (type != hwmon_temp)
> +		return 0;
> +
> +	switch (attr) {
> +	case hwmon_temp_input:
> +		return S_IRUGO;

checkpatch complains about that nowadays and asks for 0444.

> +	default:
> +		return 0;
> +	}
> +}
> +
> +static const u32 ltq_chip_config[] = {
> +	HWMON_C_REGISTER_TZ,
> +	0
> +};
> +
> +static const struct hwmon_channel_info ltq_chip = {
> +	.type = hwmon_chip,
> +	.config = ltq_chip_config,
> +};
> +
> +static const u32 ltq_temp_config[] = {
> +	HWMON_T_INPUT,
> +	0
> +};
> +
> +static const struct hwmon_channel_info ltq_temp = {
> +	.type = hwmon_temp,
> +	.config = ltq_temp_config,
> +};
> +
> +static const struct hwmon_channel_info *ltq_info[] = {
> +	&ltq_chip,
> +	&ltq_temp,
> +	NULL
> +};
> +
> +static const struct hwmon_ops ltq_hwmon_ops = {
> +	.is_visible = ltq_is_visible,
> +	.read = ltq_read,
> +};
> +
> +static const struct hwmon_chip_info ltq_chip_info = {
> +	.ops = &ltq_hwmon_ops,
> +	.info = ltq_info,
> +};
> +
> +static int ltq_cputemp_probe(struct platform_device *pdev)
> +{
> +	struct device *hwmon_dev;
> +
> +	/* available on vr9 v1.2 SoCs only */
> +	if (ltq_soc_type() != SOC_TYPE_VR9_2)
> +		return -ENODEV;
> +
> +	hwmon_dev = devm_hwmon_device_register_with_info(&pdev->dev,
> +							"CPU0",

This should be the driver name, or something that reflects the chip,
not the sensor. "lantiq" would be fine.

> +							NULL,
> +							&ltq_chip_info,
> +							NULL);

Please fix the indentation to match '('.

> +
> +	if (IS_ERR(hwmon_dev)) {
> +		dev_err(&pdev->dev, "Failed to register as hwmon device");
> +		return PTR_ERR(hwmon_dev);
> +	}
> +
> +	ltq_cputemp_enable();

Are you sure you want to enable _after_ registration ? Userspace may
have accessed the chip already here.

> +
> +	return 0;
> +}
> +
> +static int ltq_cputemp_release(struct platform_device *pdev)
> +{
> +	ltq_cputemp_disable();

I would suggest to enable the chip prior to registration, and use
devm_add_action() to disable it. This makes the code less racy,
and you can drop the release function.

> +	return 0;
> +}
> +
> +const struct of_device_id ltq_cputemp_match[] = {
> +	{ .compatible = "lantiq,cputemp" },
> +	{},
> +};
> +MODULE_DEVICE_TABLE(of, ltq_cputemp_match);
> +
> +static struct platform_driver ltq_cputemp_driver = {
> +	.probe = ltq_cputemp_probe,
> +	.remove = ltq_cputemp_release,
> +	.driver = {
> +		.name = "ltq-cputemp",
> +		.of_match_table = ltq_cputemp_match,
> +	},
> +};
> +
> +int __init init_ltq_cputemp(void)
> +{
> +	return platform_driver_register(&ltq_cputemp_driver);
> +}
> +
> +void clean_ltq_cputemp(void)
> +{
> +	platform_driver_unregister(&ltq_cputemp_driver);
> +}

I have no idea what those functions are about. Are they leftover from v1 ?

> +
> +module_platform_driver(ltq_cputemp_driver);
> +
> +MODULE_AUTHOR("Florian Eckert <fe@....tdt.de>");
> +MODULE_DESCRIPTION("Lantiq cpu temperature sensor driver");
> +MODULE_LICENSE("GPL");

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