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Sender: Guenter Roeck <groeck7@gmail.com>
Date:   Tue, 3 Jan 2023 14:10:17 -0800
From:   Guenter Roeck <linux@roeck-us.net>
To:     Hal Feng <hal.feng@starfivetech.com>
Cc:     linux-hwmon@vger.kernel.org, linux-doc@vger.kernel.org,
        linux-riscv@lists.infradead.org, devicetree@vger.kernel.org,
        Jean Delvare <jdelvare@suse.com>,
        Jonathan Corbet <corbet@lwn.net>,
        Conor Dooley <conor@kernel.org>,
        Paul Walmsley <paul.walmsley@sifive.com>,
        Palmer Dabbelt <palmer@dabbelt.com>,
        Albert Ou <aou@eecs.berkeley.edu>,
        Rob Herring <robh+dt@kernel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
        Emil Renner Berthing <emil.renner.berthing@canonical.com>,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH v1 2/4] hwmon: (sfctemp) Add StarFive JH71x0 temperature
 sensor
Message-ID: <20230103221017.GA217155@roeck-us.net>
References: <20230103013145.9570-1-hal.feng@starfivetech.com>
 <20230103013145.9570-3-hal.feng@starfivetech.com>
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In-Reply-To: <20230103013145.9570-3-hal.feng@starfivetech.com>
Precedence: bulk

On Tue, Jan 03, 2023 at 09:31:43AM +0800, Hal Feng wrote:
> From: Emil Renner Berthing <kernel@esmil.dk>
> 
> Register definitions and conversion constants based on sfctemp driver by
> Samin in the StarFive 5.10 kernel.
> 
> Signed-off-by: Emil Renner Berthing <kernel@esmil.dk>
> Co-developed-by: Samin Guo <samin.guo@starfivetech.com>
> Signed-off-by: Samin Guo <samin.guo@starfivetech.com>
> Signed-off-by: Hal Feng <hal.feng@starfivetech.com>

This is obviously version 4 of the previous patch series,
with various enhancements. Please do not "sell" that as
v1 of a new patch series. Submit it as next version,
and provide a change log.

> ---
>  Documentation/hwmon/index.rst   |   1 +
>  Documentation/hwmon/sfctemp.rst |  33 +++
>  MAINTAINERS                     |   8 +
>  drivers/hwmon/Kconfig           |  10 +
>  drivers/hwmon/Makefile          |   1 +
>  drivers/hwmon/sfctemp.c         | 350 ++++++++++++++++++++++++++++++++
>  6 files changed, 403 insertions(+)
>  create mode 100644 Documentation/hwmon/sfctemp.rst
>  create mode 100644 drivers/hwmon/sfctemp.c
> 
> diff --git a/Documentation/hwmon/index.rst b/Documentation/hwmon/index.rst
> index c1d11cf13eef..f7ede608b6e3 100644
> --- a/Documentation/hwmon/index.rst
> +++ b/Documentation/hwmon/index.rst
> @@ -179,6 +179,7 @@ Hardware Monitoring Kernel Drivers
>     sch5627
>     sch5636
>     scpi-hwmon
> +   sfctemp
>     sht15
>     sht21
>     sht3x
> diff --git a/Documentation/hwmon/sfctemp.rst b/Documentation/hwmon/sfctemp.rst
> new file mode 100644
> index 000000000000..9fbd5bb1f356
> --- /dev/null
> +++ b/Documentation/hwmon/sfctemp.rst
> @@ -0,0 +1,33 @@
> +.. SPDX-License-Identifier: GPL-2.0
> +
> +Kernel driver sfctemp
> +=====================
> +
> +Supported chips:
> + - StarFive JH7100
> + - StarFive JH7110
> +
> +Authors:
> + - Emil Renner Berthing <kernel@esmil.dk>
> +
> +Description
> +-----------
> +
> +This driver adds support for reading the built-in temperature sensor on the
> +JH7100 and JH7110 RISC-V SoCs by StarFive Technology Co. Ltd.
> +
> +``sysfs`` interface
> +-------------------
> +
> +The temperature sensor can be enabled, disabled and queried via the standard
> +hwmon interface in sysfs under ``/sys/class/hwmon/hwmonX`` for some value of
> +``X``:
> +
> +================ ==== =============================================
> +Name             Perm Description
> +================ ==== =============================================
> +temp1_enable     RW   Enable or disable temperature sensor.
> +                      Automatically enabled by the driver,
> +                      but may be disabled to save power.
> +temp1_input      RO   Temperature reading in milli-degrees Celsius.
> +================ ==== =============================================
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 85e8f83161d7..ab3cd5827b26 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -18661,6 +18661,14 @@ L:	netdev@vger.kernel.org
>  S:	Supported
>  F:	drivers/net/ethernet/sfc/
>  
> +SFCTEMP HWMON DRIVER
> +M:	Emil Renner Berthing <kernel@esmil.dk>
> +L:	linux-hwmon@vger.kernel.org
> +S:	Maintained
> +F:	Documentation/devicetree/bindings/hwmon/starfive,jh71x0-temp.yaml
> +F:	Documentation/hwmon/sfctemp.rst
> +F:	drivers/hwmon/sfctemp.c
> +
>  SFF/SFP/SFP+ MODULE SUPPORT
>  M:	Russell King <linux@armlinux.org.uk>
>  L:	netdev@vger.kernel.org
> diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
> index 7ac3daaf59ce..c6bbfcca3a14 100644
> --- a/drivers/hwmon/Kconfig
> +++ b/drivers/hwmon/Kconfig
> @@ -1910,6 +1910,16 @@ config SENSORS_STTS751
>  	  This driver can also be built as a module. If so, the module
>  	  will be called stts751.
>  
> +config SENSORS_SFCTEMP
> +	tristate "Starfive JH71x0 temperature sensor"
> +	depends on SOC_STARFIVE || COMPILE_TEST
> +	help
> +	  If you say yes here you get support for temperature sensor
> +	  on the Starfive JH71x0 SoCs.
> +
> +	  This driver can also be built as a module.  If so, the module
> +	  will be called sfctemp.
> +
>  config SENSORS_SMM665
>  	tristate "Summit Microelectronics SMM665"
>  	depends on I2C
> diff --git a/drivers/hwmon/Makefile b/drivers/hwmon/Makefile
> index 11d076cad8a2..5a4a02c5535c 100644
> --- a/drivers/hwmon/Makefile
> +++ b/drivers/hwmon/Makefile
> @@ -179,6 +179,7 @@ obj-$(CONFIG_SENSORS_SBRMI)	+= sbrmi.o
>  obj-$(CONFIG_SENSORS_SCH56XX_COMMON)+= sch56xx-common.o
>  obj-$(CONFIG_SENSORS_SCH5627)	+= sch5627.o
>  obj-$(CONFIG_SENSORS_SCH5636)	+= sch5636.o
> +obj-$(CONFIG_SENSORS_SFCTEMP)	+= sfctemp.o
>  obj-$(CONFIG_SENSORS_SL28CPLD)	+= sl28cpld-hwmon.o
>  obj-$(CONFIG_SENSORS_SHT15)	+= sht15.o
>  obj-$(CONFIG_SENSORS_SHT21)	+= sht21.o
> diff --git a/drivers/hwmon/sfctemp.c b/drivers/hwmon/sfctemp.c
> new file mode 100644
> index 000000000000..e56716ad9587
> --- /dev/null
> +++ b/drivers/hwmon/sfctemp.c
> @@ -0,0 +1,350 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright (C) 2021 Emil Renner Berthing <kernel@esmil.dk>
> + * Copyright (C) 2021 Samin Guo <samin.guo@starfivetech.com>
> + */
> +#include <linux/clk.h>
> +#include <linux/completion.h>
> +#include <linux/delay.h>
> +#include <linux/hwmon.h>
> +#include <linux/interrupt.h>
> +#include <linux/io.h>
> +#include <linux/module.h>
> +#include <linux/mutex.h>
> +#include <linux/of.h>
> +#include <linux/platform_device.h>
> +#include <linux/reset.h>
> +
> +/*
> + * TempSensor reset. The RSTN can be de-asserted once the analog core has
> + * powered up. Trst(min 100ns)
> + * 0:reset  1:de-assert
> + */
> +#define SFCTEMP_RSTN	BIT(0)

Missing include of linux/bits.h

> +
> +/*
> + * TempSensor analog core power down. The analog core will be powered up
> + * Tpu(min 50us) after PD is de-asserted. RSTN should be held low until the
> + * analog core is powered up.
> + * 0:power up  1:power down
> + */
> +#define SFCTEMP_PD	BIT(1)
> +
> +/*
> + * TempSensor start conversion enable.
> + * 0:disable  1:enable
> + */
> +#define SFCTEMP_RUN	BIT(2)
> +
> +/*
> + * TempSensor conversion value output.
> + * Temp(C)=DOUT*Y/4094 - K
> + */
> +#define SFCTEMP_DOUT_POS	16
> +#define SFCTEMP_DOUT_MSK	GENMASK(27, 16)
> +
> +/* DOUT to Celcius conversion constants */
> +#define SFCTEMP_Y1000	237500L
> +#define SFCTEMP_Z	4094L
> +#define SFCTEMP_K1000	81100L
> +
> +struct sfctemp {
> +	/* serialize access to hardware register and enabled below */
> +	struct mutex lock;
> +	struct completion conversion_done;
> +	void __iomem *regs;
> +	struct clk *clk_sense;
> +	struct clk *clk_bus;
> +	struct reset_control *rst_sense;
> +	struct reset_control *rst_bus;
> +	bool enabled;
> +};
> +
> +static irqreturn_t sfctemp_isr(int irq, void *data)
> +{
> +	struct sfctemp *sfctemp = data;
> +
> +	complete(&sfctemp->conversion_done);
> +	return IRQ_HANDLED;
> +}
> +
> +static void sfctemp_power_up(struct sfctemp *sfctemp)
> +{
> +	/* make sure we're powered down first */
> +	writel(SFCTEMP_PD, sfctemp->regs);
> +	udelay(1);
> +
> +	writel(0, sfctemp->regs);
> +	/* wait t_pu(50us) + t_rst(100ns) */
> +	usleep_range(60, 200);
> +
> +	/* de-assert reset */
> +	writel(SFCTEMP_RSTN, sfctemp->regs);
> +	udelay(1); /* wait t_su(500ps) */
> +}
> +
> +static void sfctemp_power_down(struct sfctemp *sfctemp)
> +{
> +	writel(SFCTEMP_PD, sfctemp->regs);
> +}
> +
> +static void sfctemp_run_single(struct sfctemp *sfctemp)
> +{
> +	writel(SFCTEMP_RSTN | SFCTEMP_RUN, sfctemp->regs);
> +	udelay(1);
> +	writel(SFCTEMP_RSTN, sfctemp->regs);

The datasheet (or, rather, programming manual) does not appear
to be public, so I have to guess here.

The code suggests that running a single conversion may be a choice,
not a requirement. If it is indeed a choice, the reasoning needs to be
explained since it adds a lot of complexity and dependencies to the
driver (for example, interrupt support is only mandatory or even needed
due to this choice). It also adds a significant delay to temperature
read operations, which may have practical impact on thermal control
software.

If the chip only supports single temperature readings, that needs to be
explained as well (and why SFCTEMP_RUN has to be reset in that case).

> +}
> +
> +static int sfctemp_enable(struct sfctemp *sfctemp)
> +{
> +	int ret = 0;
> +
> +	mutex_lock(&sfctemp->lock);
> +	if (sfctemp->enabled)
> +		goto done;
> +
> +	ret = clk_prepare_enable(sfctemp->clk_bus);
> +	if (ret)
> +		goto err;
> +	ret = reset_control_deassert(sfctemp->rst_bus);
> +	if (ret)
> +		goto err_disable_bus;
> +
> +	ret = clk_prepare_enable(sfctemp->clk_sense);
> +	if (ret)
> +		goto err_assert_bus;
> +	ret = reset_control_deassert(sfctemp->rst_sense);
> +	if (ret)
> +		goto err_disable_sense;
> +
> +	sfctemp_power_up(sfctemp);
> +	sfctemp->enabled = true;
> +done:
> +	mutex_unlock(&sfctemp->lock);
> +	return ret;
> +
> +err_disable_sense:
> +	clk_disable_unprepare(sfctemp->clk_sense);
> +err_assert_bus:
> +	reset_control_assert(sfctemp->rst_bus);
> +err_disable_bus:
> +	clk_disable_unprepare(sfctemp->clk_bus);
> +err:
> +	mutex_unlock(&sfctemp->lock);
> +	return ret;
> +}
> +
> +static int sfctemp_disable(struct sfctemp *sfctemp)
> +{
> +	mutex_lock(&sfctemp->lock);
> +	if (!sfctemp->enabled)
> +		goto done;
> +
> +	sfctemp_power_down(sfctemp);
> +	reset_control_assert(sfctemp->rst_sense);
> +	clk_disable_unprepare(sfctemp->clk_sense);
> +	reset_control_assert(sfctemp->rst_bus);
> +	clk_disable_unprepare(sfctemp->clk_bus);
> +	sfctemp->enabled = false;
> +done:
> +	mutex_unlock(&sfctemp->lock);
> +	return 0;
> +}
> +
> +static void sfctemp_disable_action(void *data)
> +{
> +	sfctemp_disable(data);
> +}
> +
> +static int sfctemp_convert(struct sfctemp *sfctemp, long *val)
> +{
> +	int ret;
> +
> +	mutex_lock(&sfctemp->lock);
> +	if (!sfctemp->enabled) {
> +		ret = -ENODATA;
> +		goto out;
> +	}
> +
> +	sfctemp_run_single(sfctemp);
> +
> +	ret = wait_for_completion_interruptible_timeout(&sfctemp->conversion_done,
> +							msecs_to_jiffies(10));
> +	if (ret <= 0) {
> +		if (ret == 0)
> +			ret = -ETIMEDOUT;
> +		goto out;
> +	}
> +
> +	/* calculate temperature in milli Celcius */
> +	*val = (long)((readl(sfctemp->regs) & SFCTEMP_DOUT_MSK) >> SFCTEMP_DOUT_POS)
> +		* SFCTEMP_Y1000 / SFCTEMP_Z - SFCTEMP_K1000;
> +
> +	ret = 0;
> +out:
> +	mutex_unlock(&sfctemp->lock);
> +	return ret;
> +}
> +
> +static umode_t sfctemp_is_visible(const void *data, enum hwmon_sensor_types type,
> +				  u32 attr, int channel)
> +{
> +	switch (type) {
> +	case hwmon_temp:
> +		switch (attr) {
> +		case hwmon_temp_enable:
> +			return 0644;
> +		case hwmon_temp_input:
> +			return 0444;
> +		}
> +		return 0;
> +	default:
> +		return 0;
> +	}
> +}
> +
> +static int sfctemp_read(struct device *dev, enum hwmon_sensor_types type,
> +			u32 attr, int channel, long *val)
> +{
> +	struct sfctemp *sfctemp = dev_get_drvdata(dev);
> +
> +	switch (type) {
> +	case hwmon_temp:
> +		switch (attr) {
> +		case hwmon_temp_enable:
> +			*val = sfctemp->enabled;
> +			return 0;
> +		case hwmon_temp_input:
> +			return sfctemp_convert(sfctemp, val);
> +		}
> +		return -EINVAL;
> +	default:
> +		return -EINVAL;
> +	}
> +}
> +
> +static int sfctemp_write(struct device *dev, enum hwmon_sensor_types type,
> +			 u32 attr, int channel, long val)
> +{
> +	struct sfctemp *sfctemp = dev_get_drvdata(dev);
> +
> +	switch (type) {
> +	case hwmon_temp:
> +		switch (attr) {
> +		case hwmon_temp_enable:
> +			if (val == 0)
> +				return sfctemp_disable(sfctemp);
> +			if (val == 1)
> +				return sfctemp_enable(sfctemp);
> +			break;
> +		}
> +		return -EINVAL;
> +	default:
> +		return -EINVAL;
> +	}
> +}
> +
> +static const struct hwmon_channel_info *sfctemp_info[] = {
> +	HWMON_CHANNEL_INFO(chip, HWMON_C_REGISTER_TZ),
> +	HWMON_CHANNEL_INFO(temp, HWMON_T_ENABLE | HWMON_T_INPUT),
> +	NULL
> +};
> +
> +static const struct hwmon_ops sfctemp_hwmon_ops = {
> +	.is_visible = sfctemp_is_visible,
> +	.read = sfctemp_read,
> +	.write = sfctemp_write,
> +};
> +
> +static const struct hwmon_chip_info sfctemp_chip_info = {
> +	.ops = &sfctemp_hwmon_ops,
> +	.info = sfctemp_info,
> +};
> +
> +static int sfctemp_probe(struct platform_device *pdev)
> +{
> +	struct device *dev = &pdev->dev;
> +	struct device *hwmon_dev;
> +	struct sfctemp *sfctemp;
> +	int ret;
> +
> +	sfctemp = devm_kzalloc(dev, sizeof(*sfctemp), GFP_KERNEL);
> +	if (!sfctemp)
> +		return -ENOMEM;
> +
> +	dev_set_drvdata(dev, sfctemp);
> +	mutex_init(&sfctemp->lock);
> +	init_completion(&sfctemp->conversion_done);
> +
> +	sfctemp->regs = devm_platform_ioremap_resource(pdev, 0);
> +	if (IS_ERR(sfctemp->regs))
> +		return PTR_ERR(sfctemp->regs);
> +
> +	sfctemp->clk_sense = devm_clk_get(dev, "sense");
> +	if (IS_ERR(sfctemp->clk_sense))
> +		return dev_err_probe(dev, PTR_ERR(sfctemp->clk_sense),
> +				     "error getting sense clock\n");
> +
> +	sfctemp->clk_bus = devm_clk_get(dev, "bus");
> +	if (IS_ERR(sfctemp->clk_bus))
> +		return dev_err_probe(dev, PTR_ERR(sfctemp->clk_bus),
> +				     "error getting bus clock\n");
> +
> +	sfctemp->rst_sense = devm_reset_control_get_exclusive(dev, "sense");
> +	if (IS_ERR(sfctemp->rst_sense))
> +		return dev_err_probe(dev, PTR_ERR(sfctemp->rst_sense),
> +				     "error getting sense reset\n");
> +
> +	sfctemp->rst_bus = devm_reset_control_get_exclusive(dev, "bus");
> +	if (IS_ERR(sfctemp->rst_bus))
> +		return dev_err_probe(dev, PTR_ERR(sfctemp->rst_bus),
> +				     "error getting busreset\n");
> +
> +	ret = reset_control_assert(sfctemp->rst_sense);
> +	if (ret)
> +		return dev_err_probe(dev, ret, "error asserting sense reset\n");
> +
> +	ret = reset_control_assert(sfctemp->rst_bus);
> +	if (ret)
> +		return dev_err_probe(dev, ret, "error asserting bus reset\n");
> +
> +	ret = platform_get_irq(pdev, 0);
> +	if (ret < 0)
> +		return ret;
> +
> +	ret = devm_request_irq(dev, ret, sfctemp_isr, 0, pdev->name, sfctemp);
> +	if (ret)
> +		return dev_err_probe(dev, ret, "error requesting irq\n");
> +
> +	ret = devm_add_action(dev, sfctemp_disable_action, sfctemp);
> +	if (ret)
> +		return ret;
> +
> +	ret = sfctemp_enable(sfctemp);
> +	if (ret)
> +		return dev_err_probe(dev, ret, "error enabling temperature sensor: %d\n", ret);
> +
> +	hwmon_dev = devm_hwmon_device_register_with_info(dev, pdev->name, sfctemp,
> +							 &sfctemp_chip_info, NULL);
> +	return PTR_ERR_OR_ZERO(hwmon_dev);
> +}
> +
> +static const struct of_device_id sfctemp_of_match[] = {
> +	{ .compatible = "starfive,jh7100-temp" },
> +	{ .compatible = "starfive,jh7110-temp" },
> +	{ /* sentinel */ }
> +};
> +MODULE_DEVICE_TABLE(of, sfctemp_of_match);
> +
> +static struct platform_driver sfctemp_driver = {
> +	.probe  = sfctemp_probe,
> +	.driver = {
> +		.name = "sfctemp",
> +		.of_match_table = sfctemp_of_match,
> +	},
> +};
> +module_platform_driver(sfctemp_driver);
> +
> +MODULE_AUTHOR("Emil Renner Berthing");
> +MODULE_DESCRIPTION("StarFive JH71x0 temperature sensor driver");
> +MODULE_LICENSE("GPL");