Message-ID:
 <IA1PR20MB4953DFA5607E92D16E1B31FABBB32@IA1PR20MB4953.namprd20.prod.outlook.com>
Date: Sat, 3 Aug 2024 07:28:51 +0800
From: Inochi Amaoto <inochiama@...look.com>
To: Guenter Roeck <linux@...ck-us.net>, 
	Inochi Amaoto <inochiama@...look.com>, Jean Delvare <jdelvare@...e.com>, Rob Herring <robh@...nel.org>, 
	Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>, 
	Chen Wang <unicorn_wang@...look.com>, Jonathan Corbet <corbet@....net>, 
	Paul Walmsley <paul.walmsley@...ive.com>, Palmer Dabbelt <palmer@...belt.com>, 
	Albert Ou <aou@...s.berkeley.edu>, Guo Ren <guoren@...nel.org>, Chao Wei <chao.wei@...hgo.com>, 
	Jinyu Tang <tangjinyu@...ylab.org>, Hal Feng <hal.feng@...rfivetech.com>, 
	Yangyu Chen <cyy@...self.name>, Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>
Cc: linux-hwmon@...r.kernel.org, devicetree@...r.kernel.org, 
	linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org, linux-riscv@...ts.infradead.org
Subject: Re: [PATCH v9 2/4] drivers: hwmon: sophgo: Add SG2042 external
 hardware monitor support

On Fri, Aug 02, 2024 at 06:59:22AM GMT, Guenter Roeck wrote:
> On 8/2/24 05:38, Inochi Amaoto wrote:
> > SG2042 use an external MCU to provide basic hardware information
> > and thermal sensors.
> > 
> > Add driver support for the onboard MCU of SG2042.
> > 
> > Signed-off-by: Inochi Amaoto <inochiama@...look.com>
> > Tested-by: Chen Wang <unicorn_wang@...look.com>
> > Reviewed-by: Chen Wang <unicorn_wang@...look.com>
> > ---
> >   Documentation/hwmon/index.rst      |   1 +
> >   Documentation/hwmon/sg2042-mcu.rst |  39 +++
> >   drivers/hwmon/Kconfig              |  11 +
> >   drivers/hwmon/Makefile             |   1 +
> >   drivers/hwmon/sg2042-mcu.c         | 394 +++++++++++++++++++++++++++++
> >   5 files changed, 446 insertions(+)
> >   create mode 100644 Documentation/hwmon/sg2042-mcu.rst
> >   create mode 100644 drivers/hwmon/sg2042-mcu.c
> > 
> > diff --git a/Documentation/hwmon/index.rst b/Documentation/hwmon/index.rst
> > index 913c11390a45..ea3b5be8fe4f 100644
> > --- a/Documentation/hwmon/index.rst
> > +++ b/Documentation/hwmon/index.rst
> > @@ -206,6 +206,7 @@ Hardware Monitoring Kernel Drivers
> >      sch5636
> >      scpi-hwmon
> >      sfctemp
> > +   sg2042-mcu
> >      sht15
> >      sht21
> >      sht3x
> > diff --git a/Documentation/hwmon/sg2042-mcu.rst b/Documentation/hwmon/sg2042-mcu.rst
> > new file mode 100644
> > index 000000000000..250016b47dd1
> > --- /dev/null
> > +++ b/Documentation/hwmon/sg2042-mcu.rst
> > @@ -0,0 +1,39 @@
> > +.. SPDX-License-Identifier: GPL-2.0
> > +
> > +Kernel driver sg2042-mcu
> > +=====================
> > +
> > +Supported chips:
> > +
> > +  * Onboard MCU for sg2042
> > +
> > +    Addresses scanned: -
> > +
> > +    Prefix: 'sg2042-mcu'
> > +
> > +Authors:
> > +
> > +  - Inochi Amaoto <inochiama@...look.com>
> > +
> > +Description
> > +-----------
> > +
> > +This driver supprts hardware monitoring for onboard MCU with
> > +i2c interface.
> > +
> > +Usage Notes
> > +-----------
> > +
> > +This driver does not auto-detect devices. You will have to instantiate
> > +the devices explicitly.
> > +Please see Documentation/i2c/instantiating-devices.rst for details.
> > +
> > +Sysfs Attributes
> > +----------------
> > +
> > +================= =============================================
> > +temp1_input       Measured temperature of SoC
> > +temp1_crit        Critical high temperature
> > +temp1_crit_hyst   hysteresis temperature restore from Critical
> > +temp2_input       Measured temperature of the base board
> > +================= =============================================
> > diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
> > index b60fe2e58ad6..7aa6c3f322e5 100644
> > --- a/drivers/hwmon/Kconfig
> > +++ b/drivers/hwmon/Kconfig
> > @@ -2066,6 +2066,17 @@ config SENSORS_SFCTEMP
> >   	  This driver can also be built as a module.  If so, the module
> >   	  will be called sfctemp.
> > +config SENSORS_SG2042_MCU
> > +	tristate "Sophgo onboard MCU support"
> > +	depends on I2C
> > +	depends on ARCH_SOPHGO || COMPILE_TEST
> > +	help
> > +	  Support for onboard MCU of Sophgo SG2042 SoCs. This mcu provides
> > +	  power control and some basic information.
> > +
> > +	  This driver can be built as a module. If so, the module
> > +	  will be called sg2042-mcu.
> > +
> >   config SENSORS_SURFACE_FAN
> >   	tristate "Surface Fan Driver"
> >   	depends on SURFACE_AGGREGATOR
> > diff --git a/drivers/hwmon/Makefile b/drivers/hwmon/Makefile
> > index b1c7056c37db..0bbe812a67ae 100644
> > --- a/drivers/hwmon/Makefile
> > +++ b/drivers/hwmon/Makefile
> > @@ -194,6 +194,7 @@ 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-$(CONFIG_SENSORS_SG2042_MCU) += sg2042-mcu.o
> >   obj-$(CONFIG_SENSORS_SL28CPLD)	+= sl28cpld-hwmon.o
> >   obj-$(CONFIG_SENSORS_SHT15)	+= sht15.o
> >   obj-$(CONFIG_SENSORS_SHT21)	+= sht21.o
> > diff --git a/drivers/hwmon/sg2042-mcu.c b/drivers/hwmon/sg2042-mcu.c
> > new file mode 100644
> > index 000000000000..6d8d677f86f3
> > --- /dev/null
> > +++ b/drivers/hwmon/sg2042-mcu.c
> > @@ -0,0 +1,394 @@
> > +// SPDX-License-Identifier: GPL-2.0-only
> > +/*
> > + * Copyright (c) 2024 Inochi Amaoto <inochiama@...look.com>
> > + *
> > + * Sophgo power control mcu for SG2042
> > + */
> > +
> > +#include <linux/cleanup.h>
> > +#include <linux/debugfs.h>
> > +#include <linux/err.h>
> > +#include <linux/hwmon.h>
> > +#include <linux/i2c.h>
> > +#include <linux/kernel.h>
> > +#include <linux/module.h>
> > +#include <linux/mutex.h>
> > +
> > +/* fixed MCU registers */
> > +#define REG_BOARD_TYPE				0x00
> > +#define REG_MCU_FIRMWARE_VERSION		0x01
> > +#define REG_PCB_VERSION				0x02
> > +#define REG_PWR_CTRL				0x03
> > +#define REG_SOC_TEMP				0x04
> > +#define REG_BOARD_TEMP				0x05
> > +#define REG_RST_COUNT				0x0a
> > +#define REG_UPTIME				0x0b
> > +#define REG_RESET_REASON			0x0d
> > +#define REG_MCU_TYPE				0x18
> > +#define REG_REPOWER_ACTION			0x65
> > +#define REG_CRITICAL_TEMP			0x66
> > +#define REG_REPOWER_TEMP			0x67
> > +
> > +#define REPOWER_ACTION_REBOOT			1
> > +#define REPOWER_ACTION_POWEROFF			2
> > +
> > +#define MCU_POWER_MAX				0xff
> > +
> > +#define DEFINE_MCU_DEBUG_ATTR(_name, _reg, _format)			\
> > +	static int _name##_show(struct seq_file *seqf,			\
> > +				    void *unused)			\
> > +	{								\
> > +		struct sg2042_mcu_data *mcu = seqf->private;		\
> > +		int ret;						\
> > +		ret = i2c_smbus_read_byte_data(mcu->client, (_reg));	\
> > +		if (ret < 0)						\
> > +			return ret;					\
> > +		seq_printf(seqf, _format "\n", ret);			\
> > +		return 0;						\
> > +	}								\
> > +	DEFINE_SHOW_ATTRIBUTE(_name)					\
> > +
> > +struct sg2042_mcu_data {
> > +	struct i2c_client	*client;
> > +	struct dentry		*debugfs;
> > +	struct mutex		mutex;
> > +};
> > +
> > +static struct dentry *sgmcu_debugfs;
> > +
> > +static ssize_t reset_count_show(struct device *dev,
> > +				struct device_attribute *attr,
> > +				char *buf)
> > +{
> > +	struct sg2042_mcu_data *mcu = dev_get_drvdata(dev);
> > +	int ret;
> > +
> > +	ret = i2c_smbus_read_byte_data(mcu->client, REG_RST_COUNT);
> > +	if (ret < 0)
> > +		return ret;
> > +
> > +	return sprintf(buf, "%d\n", ret);
> > +}
> > +
> > +static ssize_t uptime_show(struct device *dev,
> > +			   struct device_attribute *attr,
> > +			   char *buf)
> > +{
> > +	struct sg2042_mcu_data *mcu = dev_get_drvdata(dev);
> > +	u8 time_val[2];
> > +	int ret;
> > +
> > +	ret = i2c_smbus_read_i2c_block_data(mcu->client, REG_UPTIME,
> > +					    sizeof(time_val), time_val);
> > +	if (ret < 0)
> > +		return ret;
> > +
> > +	return sprintf(buf, "%d\n",
> > +		       (int)(time_val[0]) + (int)(time_val[1] << 8));
> 
> Pointless type casts
> 
> > +}
> > +
> > +static ssize_t reset_reason_show(struct device *dev,
> > +				 struct device_attribute *attr,
> > +				 char *buf)
> > +{
> > +	struct sg2042_mcu_data *mcu = dev_get_drvdata(dev);
> > +	int ret;
> > +
> > +	ret = i2c_smbus_read_byte_data(mcu->client, REG_RESET_REASON);
> > +	if (ret < 0)
> > +		return ret;
> > +
> > +	return sprintf(buf, "0x%02x\n", ret);
> > +}
> > +
> > +static ssize_t repower_action_show(struct device *dev,
> > +				   struct device_attribute *attr,
> > +				   char *buf)
> > +{
> > +	struct sg2042_mcu_data *mcu = dev_get_drvdata(dev);
> > +	int ret;
> > +	const char *action;
> > +
> > +	ret = i2c_smbus_read_byte_data(mcu->client, REG_REPOWER_ACTION);
> > +	if (ret < 0)
> > +		return ret;
> > +
> > +	if (ret == REPOWER_ACTION_REBOOT)
> > +		action = "reboot";
> > +	else if (ret == REPOWER_ACTION_POWEROFF)
> > +		action = "poweroff";
> > +	else
> > +		action = "unknown";
> > +
> > +	return sprintf(buf, "%s\n", action);
> > +}
> > +
> > +static ssize_t repower_action_store(struct device *dev,
> > +				    struct device_attribute *attr,
> > +				    const char *buf, size_t count)
> > +{
> > +	struct sg2042_mcu_data *mcu = dev_get_drvdata(dev);
> > +	u8 value;
> > +	int ret;
> > +
> > +	if (sysfs_streq("reboot", buf))
> > +		value = REPOWER_ACTION_REBOOT;
> > +	else if (sysfs_streq("poweroff", buf))
> > +		value = REPOWER_ACTION_POWEROFF;
> > +	else
> > +		return -EINVAL;
> > +
> > +	guard(mutex)(&mcu->mutex);
> > +
> Pointless mutex protection.
> 

OK, I have seen the protection in the i2c bus. I will remove this.

> > +	ret = i2c_smbus_write_byte_data(mcu->client,
> > +					REG_REPOWER_ACTION, value);
> > +	if (ret < 0)
> > +		return ret;
> > +
> > +	return count;
> > +}
> > +
> > +static DEVICE_ATTR_RO(reset_count);
> > +static DEVICE_ATTR_RO(uptime);
> > +static DEVICE_ATTR_RO(reset_reason);
> > +static DEVICE_ATTR_RW(repower_action);
> > +
> > +DEFINE_MCU_DEBUG_ATTR(firmware_version, REG_MCU_FIRMWARE_VERSION, "0x%02x");
> > +DEFINE_MCU_DEBUG_ATTR(pcb_version, REG_PCB_VERSION, "0x%02x");
> > +DEFINE_MCU_DEBUG_ATTR(board_type, REG_BOARD_TYPE, "0x%02x");
> > +DEFINE_MCU_DEBUG_ATTR(mcu_type, REG_MCU_TYPE, "%d");
> > +
> > +static struct attribute *sg2042_mcu_attrs[] = {
> > +	&dev_attr_reset_count.attr,
> > +	&dev_attr_uptime.attr,
> > +	&dev_attr_reset_reason.attr,
> > +	&dev_attr_repower_action.attr,
> > +	NULL
> > +};
> > +
> > +static const struct attribute_group sg2042_mcu_attr_group = {
> > +	.attrs	= sg2042_mcu_attrs,
> > +};
> > +
> > +static const struct attribute_group *sg2042_mcu_groups[] = {
> > +	&sg2042_mcu_attr_group,
> > +	NULL
> > +};
> > +
> > +static const struct hwmon_channel_info * const sg2042_mcu_info[] = {
> > +	HWMON_CHANNEL_INFO(chip, HWMON_C_REGISTER_TZ),
> > +	HWMON_CHANNEL_INFO(temp, HWMON_T_INPUT | HWMON_T_CRIT |
> > +					HWMON_T_CRIT_HYST,
> > +				 HWMON_T_INPUT),
> > +	NULL
> > +};
> > +
> > +static int sg2042_mcu_read(struct device *dev,
> > +			   enum hwmon_sensor_types type,
> > +			   u32 attr, int channel, long *val)
> > +{
> > +	struct sg2042_mcu_data *mcu = dev_get_drvdata(dev);
> > +	int tmp;
> > +	u8 reg;
> > +
> > +	switch (attr) {
> > +	case hwmon_temp_input:
> > +		reg = channel ? REG_BOARD_TEMP : REG_SOC_TEMP;
> > +		break;
> > +	case hwmon_temp_crit:
> > +		reg = REG_CRITICAL_TEMP;
> > +		break;
> > +	case hwmon_temp_crit_hyst:
> > +		reg = REG_REPOWER_TEMP;
> > +		break;
> > +	default:
> > +		return -EOPNOTSUPP;
> > +	}
> > +
> > +	tmp = i2c_smbus_read_byte_data(mcu->client, reg);
> > +	if (tmp < 0)
> > +		return tmp;
> > +	*val = tmp * 1000;
> > +
> > +	return 0;
> > +}
> > +
> > +static int sg2042_mcu_write(struct device *dev,
> > +			    enum hwmon_sensor_types type,
> > +			    u32 attr, int channel, long val)
> > +{
> > +	struct sg2042_mcu_data *mcu = dev_get_drvdata(dev);
> > +	int temp = val / 1000;
> > +	int hyst_temp, crit_temp;
> > +	u8 reg;
> > +
> > +	if (temp > MCU_POWER_MAX)
> > +		temp = MCU_POWER_MAX;
> > +	else if (temp < 0)
> > +		temp = 0;
> > +
> 	temp = clamp_val(temp, 0, MCU_POWER_MAX);
> 
> > +	guard(mutex)(&mcu->mutex);
> > +
> > +	switch (attr) {
> > +	case hwmon_temp_crit:
> > +		hyst_temp = i2c_smbus_read_byte_data(mcu->client,
> > +						     REG_REPOWER_TEMP);
> > +		if (hyst_temp < 0)
> > +			return hyst_temp;
> > +
> > +		crit_temp = temp;
> > +		reg = REG_CRITICAL_TEMP;
> > +		break;
> > +	case hwmon_temp_crit_hyst:
> > +		crit_temp = i2c_smbus_read_byte_data(mcu->client,
> > +						     REG_CRITICAL_TEMP);
> > +		if (crit_temp < 0)
> > +			return crit_temp;
> > +
> > +		hyst_temp = temp;
> > +		reg = REG_REPOWER_TEMP;
> > +		break;
> > +	default:
> > +		return -EOPNOTSUPP;
> > +	}
> > +
> > +	/*
> > +	 * ensure hyst_temp is smaller to avoid MCU from
> > +	 * keeping triggering repower event.
> > +	 */
> > +	if (crit_temp < hyst_temp)
> > +		return -EINVAL;
> > +
> > +	return i2c_smbus_write_byte_data(mcu->client, reg, temp);
> > +}
> > +
> > +static umode_t sg2042_mcu_is_visible(const void *_data,
> > +				     enum hwmon_sensor_types type,
> > +				     u32 attr, int channel)
> > +{
> > +	switch (type) {
> > +	case hwmon_temp:
> > +		switch (attr) {
> > +		case hwmon_temp_input:
> > +			return 0444;
> > +		case hwmon_temp_crit:
> > +		case hwmon_temp_crit_hyst:
> > +			if (channel == 0)
> > +				return 0664;
> > +			break;
> 
> In practice this is the only break; in this nested switch sequence,
> making the return 0; at the end necessary.
> 
> Please either use break; always when returning 0, or return 0 here
> as well and drop the final return 0;
> 

Thanks, but I have a question: as this break can be fallthrough to the
default, is it better to use break;/return 0;, or just remove this
break; and let it fallthrough?

> > +		default:
> > +			return 0;
> > +		}
> > +		break;
> > +	default:
> > +		return 0;
> > +	}
> > +	return 0;
> > +}
> > +
> > +static const struct hwmon_ops sg2042_mcu_ops = {
> > +	.is_visible = sg2042_mcu_is_visible,
> > +	.read = sg2042_mcu_read,
> > +	.write = sg2042_mcu_write,
> > +};
> > +
> > +static const struct hwmon_chip_info sg2042_mcu_chip_info = {
> > +	.ops = &sg2042_mcu_ops,
> > +	.info = sg2042_mcu_info,
> > +};
> > +
> > +static void sg2042_mcu_debugfs_init(struct sg2042_mcu_data *mcu,
> > +				    struct device *dev)
> > +{
> > +	mcu->debugfs = debugfs_create_dir(dev_name(dev), sgmcu_debugfs);
> > +	if (mcu->debugfs) {
> 
> debugfs_create_dir() returns an ERR_PTR(), which is checked in debugfs_create_file().
> This if() is pointless.
> 

Thanks.

> > +		debugfs_create_file("firmware_version", 0444, mcu->debugfs,
> > +				    mcu, &firmware_version_fops);
> > +		debugfs_create_file("pcb_version", 0444, mcu->debugfs, mcu,
> > +				    &pcb_version_fops);
> > +		debugfs_create_file("mcu_type", 0444, mcu->debugfs, mcu,
> > +				    &mcu_type_fops);
> > +		debugfs_create_file("board_type", 0444, mcu->debugfs, mcu,
> > +				    &board_type_fops);
> > +	}
> > +}
> > +
> > +static int sg2042_mcu_i2c_probe(struct i2c_client *client)
> > +{
> > +	struct device *dev = &client->dev;
> > +	struct sg2042_mcu_data *mcu;
> > +	struct device *hwmon_dev;
> > +
> > +	if (!i2c_check_functionality(client->adapter, I2C_FUNC_SMBUS_BYTE_DATA |
> > +						I2C_FUNC_SMBUS_BLOCK_DATA))
> > +		return -EIO;
> > +
> 		return -ENODEV;
> 
> > +	mcu = devm_kmalloc(dev, sizeof(*mcu), GFP_KERNEL);
> > +	if (!mcu)
> > +		return -ENOMEM;
> > +
> > +	mutex_init(&mcu->mutex);
> > +	mcu->client = client;
> > +
> > +	i2c_set_clientdata(client, mcu);
> > +
> > +	hwmon_dev = devm_hwmon_device_register_with_info(dev, "sg2042_mcu",
> > +							 mcu,
> > +							 &sg2042_mcu_chip_info,
> > +							 NULL);
> > +	if (IS_ERR_OR_NULL(hwmon_dev))
> > +		return -EFAULT;
> 
> devm_hwmon_device_register_with_info() returns an ERR_PTR(), and
> returning -EFAULT instead of it is more than wrong (this does not indicate
> a "bad address"). This needs to be
> 
> 	if (IS_ERR(hwmon_dev))
> 		return PTR_ERR(hwmon_dev);
> 
> I am sure I asked before not to overwrite error codes.

Yes, you have asked, it seems that I have missed this code when I
check the driver. I apology for this mistake and thanks for your
reminder.

> 
> > +
> > +	sg2042_mcu_debugfs_init(mcu, dev);
> > +
> > +	return 0;
> > +}
> > +
> > +static void sg2042_mcu_i2c_remove(struct i2c_client *client)
> > +{
> > +	struct sg2042_mcu_data *mcu = i2c_get_clientdata(client);
> > +
> > +	debugfs_remove_recursive(mcu->debugfs);
> > +}
> > +
> > +static const struct i2c_device_id sg2042_mcu_id[] = {
> > +	{ "sg2042-hwmon-mcu", 0 },
> > +	{},
> > +};
> > +MODULE_DEVICE_TABLE(i2c, sg2042_mcu_id);
> > +
> > +static const struct of_device_id sg2042_mcu_of_id[] = {
> > +	{ .compatible = "sophgo,sg2042-hwmon-mcu" },
> > +	{},
> > +};
> > +MODULE_DEVICE_TABLE(of, sg2042_mcu_of_id);
> > +
> > +static struct i2c_driver sg2042_mcu_driver = {
> > +	.driver = {
> > +		.name = "sg2042-mcu",
> > +		.of_match_table = sg2042_mcu_of_id,
> > +		.dev_groups = sg2042_mcu_groups,
> > +	},
> > +	.probe = sg2042_mcu_i2c_probe,
> > +	.remove = sg2042_mcu_i2c_remove,
> > +	.id_table = sg2042_mcu_id,
> > +};
> > +
> > +static int __init sg2042_mcu_init(void)
> > +{
> > +	sgmcu_debugfs = debugfs_create_dir("sg2042-mcu", NULL);
> > +	return i2c_add_driver(&sg2042_mcu_driver);
> > +}
> > +
> > +static void __exit sg2042_mcu_exit(void)
> > +{
> > +	debugfs_remove_recursive(sgmcu_debugfs);
> > +	i2c_del_driver(&sg2042_mcu_driver);
> > +}
> > +
> > +module_init(sg2042_mcu_init);
> > +module_exit(sg2042_mcu_exit);
> > +
> > +MODULE_AUTHOR("Inochi Amaoto <inochiama@...look.com>");
> > +MODULE_DESCRIPTION("MCU I2C driver for SG2042 soc platform");
> > +MODULE_LICENSE("GPL");
> 

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