Re: [PATCH v1 6/9] hwmon: Add Nuvoton NCT6694 HWMON support

[Guenter Roeck <linux@xxxxxxxxxxxx>]

On 10/24/24 02:20, Kalesh Anakkur Purayil wrote:
> On Thu, Oct 24, 2024 at 2:33 PM Ming Yu <a0282524688@xxxxxxxxx> wrote:
> > This driver supports Hardware monitor functionality for NCT6694 MFD
> > device based on USB interface.
> >
> > Signed-off-by: Ming Yu <tmyu0@xxxxxxxxxxx>
> > ---
> >   MAINTAINERS                   |   1 +
> >   drivers/hwmon/Kconfig         |  10 +
> >   drivers/hwmon/Makefile        |   1 +
> >   drivers/hwmon/nct6694-hwmon.c | 407 ++++++++++++++++++++++++++++++++++
> >   4 files changed, 419 insertions(+)
> >   create mode 100644 drivers/hwmon/nct6694-hwmon.c
> >
> > diff --git a/MAINTAINERS b/MAINTAINERS
> > index 63387c0d4ab6..2aa87ad84156 100644
> > --- a/MAINTAINERS
> > +++ b/MAINTAINERS
> > @@ -16439,6 +16439,7 @@ M:      Ming Yu <tmyu0@xxxxxxxxxxx>
> >   L:     linux-kernel@xxxxxxxxxxxxxxx
> >   S:     Supported
> >   F:     drivers/gpio/gpio-nct6694.c
> > +F:     drivers/hwmon/nct6694-hwmon.c
> >   F:     drivers/i2c/busses/i2c-nct6694.c
> >   F:     drivers/mfd/nct6694.c
> >   F:     drivers/net/can/nct6694_canfd.c
> > diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
> > index 08a3c863f80a..740e4afe6582 100644
> > --- a/drivers/hwmon/Kconfig
> > +++ b/drivers/hwmon/Kconfig
> > @@ -1625,6 +1625,16 @@ config SENSORS_NCT6683
> >            This driver can also be built as a module. If so, the module
> >            will be called nct6683.
> >
> > +config SENSORS_NCT6694
> > +       tristate "Nuvoton NCT6694 Hardware Monitor support"
> > +       depends on MFD_NCT6694
> > +       help
> > +         Say Y here to support Nuvoton NCT6694 hardware monitoring
> > +         functionality.
> > +
> > +         This driver can also be built as a module. If so, the module
> > +         will be called nct6694-hwmon.
> > +
> >   config SENSORS_NCT6775_CORE
> >          tristate
> >          select REGMAP
> > diff --git a/drivers/hwmon/Makefile b/drivers/hwmon/Makefile
> > index 9554d2fdcf7b..729961176d00 100644
> > --- a/drivers/hwmon/Makefile
> > +++ b/drivers/hwmon/Makefile
> > @@ -167,6 +167,7 @@ obj-$(CONFIG_SENSORS_MLXREG_FAN) += mlxreg-fan.o
> >   obj-$(CONFIG_SENSORS_MENF21BMC_HWMON) += menf21bmc_hwmon.o
> >   obj-$(CONFIG_SENSORS_MR75203)  += mr75203.o
> >   obj-$(CONFIG_SENSORS_NCT6683)  += nct6683.o
> > +obj-$(CONFIG_SENSORS_NCT6694)  += nct6694-hwmon.o
> >   obj-$(CONFIG_SENSORS_NCT6775_CORE) += nct6775-core.o
> >   nct6775-objs                   := nct6775-platform.o
> >   obj-$(CONFIG_SENSORS_NCT6775)  += nct6775.o
> > diff --git a/drivers/hwmon/nct6694-hwmon.c b/drivers/hwmon/nct6694-hwmon.c
> > new file mode 100644
> > index 000000000000..7d7d22a650b0
> > --- /dev/null
> > +++ b/drivers/hwmon/nct6694-hwmon.c
> > @@ -0,0 +1,407 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +/*
> > + * Nuvoton NCT6694 HWMON driver based on USB interface.
> > + *
> > + * Copyright (C) 2024 Nuvoton Technology Corp.
> > + */
> > +
> > +#include <linux/slab.h>
> > +#include <linux/kernel.h>
> > +#include <linux/module.h>
> > +#include <linux/hwmon.h>
> > +#include <linux/platform_device.h>
> > +#include <linux/mfd/nct6694.h>
> > +
> > +#define DRVNAME "nct6694-hwmon"
> > +
> > +/* Host interface */
> > +#define REQUEST_RPT_MOD                        0xFF
> > +#define REQUEST_HWMON_MOD              0x00
> > +
> > +/* Report Channel */
> > +#define HWMON_FIN_IDX(x)               (0x50 + ((x) * 2))
> > +#define HWMON_FIN_STS(x)               (0x6E + (x))
> > +#define HWMON_PWM_IDX(x)               (0x70 + (x))
> > +
> > +/* Message Channel*/
> > +/* Command 00h */
> > +#define REQUEST_HWMON_CMD0_LEN         0x40
> > +#define REQUEST_HWMON_CMD0_OFFSET      0x0000  /* OFFSET = SEL|CMD */
> > +#define HWMON_FIN_EN(x)                        (0x04 + (x))
> > +#define HWMON_PWM_FREQ_IDX(x)          (0x30 + (x))
> > +/* Command 02h */
> > +#define REQUEST_HWMON_CMD2_LEN         0x90
> > +#define REQUEST_HWMON_CMD2_OFFSET      0x0002  /* OFFSET = SEL|CMD */
> > +#define HWMON_SMI_CTRL_IDX             0x00
> > +#define HWMON_FIN_LIMIT_IDX(x)         (0x70 + ((x) * 2))
> > +#define HWMON_CMD2_HYST_MASK           0x1F
> > +/* Command 03h */
> > +#define REQUEST_HWMON_CMD3_LEN         0x08
> > +#define REQUEST_HWMON_CMD3_OFFSET      0x0003  /* OFFSET = SEL|CMD */
> > +
> > +struct nct6694_hwmon_data {
> > +       struct nct6694 *nct6694;
> > +
> > +       /* Make sure read & write commands are consecutive */
> > +       struct mutex hwmon_lock;
> > +};
> > +
> > +#define NCT6694_HWMON_FAN_CONFIG (HWMON_F_ENABLE | HWMON_F_INPUT | \
> > +                                 HWMON_F_MIN | HWMON_F_MIN_ALARM)
> > +#define NCT6694_HWMON_PWM_CONFIG (HWMON_PWM_INPUT | HWMON_PWM_FREQ)
> > +
> > +static const struct hwmon_channel_info *nct6694_info[] = {
> > +       HWMON_CHANNEL_INFO(fan,
> > +                          NCT6694_HWMON_FAN_CONFIG,    /* FIN0 */
> > +                          NCT6694_HWMON_FAN_CONFIG,    /* FIN1 */
> > +                          NCT6694_HWMON_FAN_CONFIG,    /* FIN2 */
> > +                          NCT6694_HWMON_FAN_CONFIG,    /* FIN3 */
> > +                          NCT6694_HWMON_FAN_CONFIG,    /* FIN4 */
> > +                          NCT6694_HWMON_FAN_CONFIG,    /* FIN5 */
> > +                          NCT6694_HWMON_FAN_CONFIG,    /* FIN6 */
> > +                          NCT6694_HWMON_FAN_CONFIG,    /* FIN7 */
> > +                          NCT6694_HWMON_FAN_CONFIG,    /* FIN8 */
> > +                          NCT6694_HWMON_FAN_CONFIG),   /* FIN9 */
> > +
> > +       HWMON_CHANNEL_INFO(pwm,
> > +                          NCT6694_HWMON_PWM_CONFIG,    /* PWM0 */
> > +                          NCT6694_HWMON_PWM_CONFIG,    /* PWM1 */
> > +                          NCT6694_HWMON_PWM_CONFIG,    /* PWM2 */
> > +                          NCT6694_HWMON_PWM_CONFIG,    /* PWM3 */
> > +                          NCT6694_HWMON_PWM_CONFIG,    /* PWM4 */
> > +                          NCT6694_HWMON_PWM_CONFIG,    /* PWM5 */
> > +                          NCT6694_HWMON_PWM_CONFIG,    /* PWM6 */
> > +                          NCT6694_HWMON_PWM_CONFIG,    /* PWM7 */
> > +                          NCT6694_HWMON_PWM_CONFIG,    /* PWM8 */
> > +                          NCT6694_HWMON_PWM_CONFIG),   /* PWM9 */
> > +       NULL
> > +};
> > +
> > +static int nct6694_fan_read(struct device *dev, u32 attr, int channel,
> > +                           long *val)
> > +{
> > +       struct nct6694_hwmon_data *data = dev_get_drvdata(dev);
> > +       unsigned char buf[2];
> > +       int ret;
> > +
> > +       switch (attr) {
> > +       case hwmon_fan_enable:
> > +               ret = nct6694_read_msg(data->nct6694, REQUEST_HWMON_MOD,
> > +                                      REQUEST_HWMON_CMD0_OFFSET,
> > +                                      REQUEST_HWMON_CMD0_LEN,
> > +                                      HWMON_FIN_EN(channel / 8),
> > +                                      1, buf);
> > +               if (ret)
> > +                       return -EINVAL;
> > +
> > +               *val = buf[0] & BIT(channel % 8) ? 1 : 0;
> > +
> > +               break;
> > +
> > +       case hwmon_fan_input:
> > +               ret = nct6694_read_msg(data->nct6694, REQUEST_RPT_MOD,
> > +                                      HWMON_FIN_IDX(channel), 2, 0,
> > +                                      2, buf);
> > +               if (ret)
> > +                       return -EINVAL;
> > +
> > +               *val = (buf[1] | (buf[0] << 8)) & 0xFFFF;
> > +
> > +               break;
> > +
> > +       case hwmon_fan_min:
> > +               ret = nct6694_read_msg(data->nct6694, REQUEST_HWMON_MOD,
> > +                                      REQUEST_HWMON_CMD2_OFFSET,
> > +                                      REQUEST_HWMON_CMD2_LEN,
> > +                                      HWMON_FIN_LIMIT_IDX(channel),
> > +                                      2, buf);
> > +               if (ret)
> > +                       return -EINVAL;
> > +
> > +               *val = (buf[1] | (buf[0] << 8)) & 0xFFFF;
> > +
> > +               break;
> > +
> > +       case hwmon_fan_min_alarm:
> > +               ret = nct6694_read_msg(data->nct6694, REQUEST_RPT_MOD,
> > +                                      HWMON_FIN_STS(channel / 8),
> > +                                      1, 0, 1, buf);
> > +               if (ret)
> > +                       return -EINVAL;
> > +
> > +               *val = buf[0] & BIT(channel % 8);
> > +
> > +               break;
> > +
> > +       default:
> > +               return -EOPNOTSUPP;
> > +       }
> > +
> > +       return 0;
> > +}
> > +
> > +static int nct6694_pwm_read(struct device *dev, u32 attr, int channel,
> > +                           long *val)
> > +{
> > +       struct nct6694_hwmon_data *data = dev_get_drvdata(dev);
> > +       unsigned char buf;
> > +       int ret;
> > +
> > +       switch (attr) {
> > +       case hwmon_pwm_input:
> > +               ret = nct6694_read_msg(data->nct6694, REQUEST_RPT_MOD,
> > +                                      HWMON_PWM_IDX(channel),
> > +                                      1, 0, 1, &buf);
> > +               if (ret)
> > +                       return -EINVAL;
> > +
> > +               *val = buf;
> > +
> > +               break;
> > +       case hwmon_pwm_freq:
> > +               ret = nct6694_read_msg(data->nct6694, REQUEST_HWMON_MOD,
> > +                                      REQUEST_HWMON_CMD0_OFFSET,
> > +                                      REQUEST_HWMON_CMD0_LEN,
> > +                                      HWMON_PWM_FREQ_IDX(channel),
> > +                                      1, &buf);
> > +               if (ret)
> > +                       return -EINVAL;
> > +
> > +               *val = buf * 25000 / 255;
> > +
> > +               break;
> > +
> > +       default:
> > +               return -EOPNOTSUPP;
> > +       }
> > +
> > +       return 0;
> > +}
> > +
> > +static int nct6694_fan_write(struct device *dev, u32 attr, int channel,
> > +                            long val)
> > +{
> > +       struct nct6694_hwmon_data *data = dev_get_drvdata(dev);
> > +       unsigned char enable_buf[REQUEST_HWMON_CMD0_LEN] = {0};
> [Kalesh] Please try to maintain RCT order for variable declaration

Ok, but that is already the case here ?

> > +       unsigned char buf[REQUEST_HWMON_CMD2_LEN] = {0};
> > +       u16 fan_val = (u16)val;
> > +       int ret;
> > +
> > +       switch (attr) {
> > +       case hwmon_fan_enable:
> > +               mutex_lock(&data->hwmon_lock);
> > +               ret = nct6694_read_msg(data->nct6694, REQUEST_HWMON_MOD,
> > +                                      REQUEST_HWMON_CMD0_OFFSET,
> > +                                      REQUEST_HWMON_CMD0_LEN, 0,
> > +                                      REQUEST_HWMON_CMD0_LEN,
> > +                                      enable_buf);
> > +               if (ret)
> > +                       goto err;
> > +
> > +               if (val)
> > +                       enable_buf[HWMON_FIN_EN(channel / 8)] |= BIT(channel % 8);
> > +               else
> > +                       enable_buf[HWMON_FIN_EN(channel / 8)] &= ~BIT(channel % 8);
> > +
> > +               ret = nct6694_write_msg(data->nct6694, REQUEST_HWMON_MOD,
> > +                                       REQUEST_HWMON_CMD0_OFFSET,
> > +                                       REQUEST_HWMON_CMD0_LEN, enable_buf);
> > +               if (ret)
> > +                       goto err;
> > +
> > +               break;
> > +
> > +       case hwmon_fan_min:
> > +               mutex_lock(&data->hwmon_lock);
> > +               ret = nct6694_read_msg(data->nct6694, REQUEST_HWMON_MOD,
> > +                                      REQUEST_HWMON_CMD2_OFFSET,
> > +                                      REQUEST_HWMON_CMD2_LEN, 0,
> > +                                      REQUEST_HWMON_CMD2_LEN, buf);
> > +               if (ret)
> > +                       goto err;
> > +
> > +               buf[HWMON_FIN_LIMIT_IDX(channel)] = (u8)((fan_val >> 8) & 0xFF);
> > +               buf[HWMON_FIN_LIMIT_IDX(channel) + 1] = (u8)(fan_val & 0xFF);
> > +               ret = nct6694_write_msg(data->nct6694, REQUEST_HWMON_MOD,
> > +                                       REQUEST_HWMON_CMD2_OFFSET,
> > +                                       REQUEST_HWMON_CMD2_LEN, buf);
> > +               if (ret)
> > +                       goto err;
> > +
> > +               break;
> > +
> > +       default:
> > +               ret = -EOPNOTSUPP;
> [Kalesh] If you initialize "ret = -EOPNOTSUPP;" during declararion,
> you can just break from here.

You are missing the point. The lock wasn't acquired here in the first place.
It is conceptually wrong to acquire a lock in the switch statement and release
it outside. This patch is a case in point.

> > +               goto err;
> > +       }
> > +
> > +err:
> > +       mutex_unlock(&data->hwmon_lock);
> > +       return ret;
> > +}
> > +
> > +static int nct6694_read(struct device *dev, enum hwmon_sensor_types type,
> > +                       u32 attr, int channel, long *val)
> > +{
> > +       switch (type) {
> > +       case hwmon_fan: /* in RPM */
> > +               return nct6694_fan_read(dev, attr, channel, val);
> > +
> > +       case hwmon_pwm: /* in value 0~255 */
> > +               return nct6694_pwm_read(dev, attr, channel, val);
> > +
> > +       default:
> > +               return -EOPNOTSUPP;
> > +       }
> > +
> > +       return 0;
> > +}
> > +
> > +static int nct6694_write(struct device *dev, enum hwmon_sensor_types type,
> > +                        u32 attr, int channel, long val)
> > +{
> > +       switch (type) {
> > +       case hwmon_fan:
> > +               return nct6694_fan_write(dev, attr, channel, val);
> > +       default:
> > +               return -EOPNOTSUPP;
> > +       }
> [Kalesh] You can use simple if condition here than a switch like:
> if (type != hwmon_fan)
>           return -EOPNOTSUPP;
> return nct6694_fan_write(dev, attr, channel, val);

That is a bit POV. I'd leave that to the developer.
More important is that the return statements after the switch are unnecessary
and never reached if each case returns immediately.

> > +
> > +       return 0;
> > +}
> > +
> > +static umode_t nct6694_is_visible(const void *data, enum hwmon_sensor_types type,
> > +                                 u32 attr, int channel)
> > +{
> > +       switch (type) {
> > +       case hwmon_fan:
> > +               switch (attr) {
> > +               case hwmon_fan_enable:
> > +               case hwmon_fan_min:
> > +                       return 0644;
> [Kalesh] I think there is no need to leave a new line in between cases
> > +
> > +               case hwmon_fan_input:
> > +               case hwmon_fan_min_alarm:
> > +                       return 0444;
> > +
> > +               default:
> > +                       return 0;
> > +               }
> > +
> > +       case hwmon_pwm:
> > +               switch (attr) {
> > +               case hwmon_pwm_input:
> > +               case hwmon_pwm_freq:
> > +                       return 0444;
> > +               default:
> > +                       return 0;
> > +               }
> > +
> > +       default:
> > +               return 0;
> > +       }
> > +
> > +       return 0;
> [Kalesh] This return statement looks redundant as the execution never
> reaches here. Same comment applies to other functions above as well.
> > +}
> > +
> > +static const struct hwmon_ops nct6694_hwmon_ops = {
> > +       .is_visible = nct6694_is_visible,
> > +       .read = nct6694_read,
> > +       .write = nct6694_write,
> > +};
> > +
> > +static const struct hwmon_chip_info nct6694_chip_info = {
> > +       .ops = &nct6694_hwmon_ops,
> > +       .info = nct6694_info,
> > +};
> > +
> > +static int nct6694_hwmon_init(struct nct6694_hwmon_data *data)
> > +{
> > +       unsigned char buf[REQUEST_HWMON_CMD2_LEN] = {0};
> > +       int ret;
> > +
> > +       /* Set Fan input Real Time alarm mode */
> > +       mutex_lock(&data->hwmon_lock);
> > +       ret = nct6694_read_msg(data->nct6694, REQUEST_HWMON_MOD,
> > +                              REQUEST_HWMON_CMD2_OFFSET,
> > +                              REQUEST_HWMON_CMD2_LEN, 0,
> > +                              REQUEST_HWMON_CMD2_LEN, buf);
> > +       if (ret)
> > +               goto err;
> [Kalesh] It would be better to rename the label as "unlock". Same
> comment on other functions as well.

The lock is not needed here in the first place. The function is called
exactly once during initialization.

> > +
> > +       buf[HWMON_SMI_CTRL_IDX] = 0x02;
> > +
> > +       ret = nct6694_write_msg(data->nct6694, REQUEST_HWMON_MOD,
> > +                               REQUEST_HWMON_CMD2_OFFSET,
> > +                               REQUEST_HWMON_CMD2_LEN, buf);
> > +       if (ret)
> > +               goto err;
> > +
> > +err:
> > +       mutex_unlock(&data->hwmon_lock);
> > +       return ret;
> > +}
> > +
> > +static int nct6694_hwmon_probe(struct platform_device *pdev)
> > +{
> > +       struct nct6694_hwmon_data *data;
> > +       struct nct6694 *nct6694 = dev_get_drvdata(pdev->dev.parent);
> > +       struct device *hwmon_dev;
> > +       int ret;
> > +
> > +       data = devm_kzalloc(&pdev->dev, sizeof(*data), GFP_KERNEL);
> > +       if (!data)
> > +               return -ENOMEM;
> > +
> > +       data->nct6694 = nct6694;
> > +       mutex_init(&data->hwmon_lock);
> > +       platform_set_drvdata(pdev, data);
> > +
> > +       ret = nct6694_hwmon_init(data);
> > +       if (ret)
> > +               return -EIO;
> > +
> > +       /* Register hwmon device to HWMON framework */
> > +       hwmon_dev = devm_hwmon_device_register_with_info(&pdev->dev,
> > +                                                        "nct6694", data,
> > +                                                        &nct6694_chip_info,
> > +                                                        NULL);
> > +       if (IS_ERR(hwmon_dev)) {
> > +               dev_err(&pdev->dev, "%s: Failed to register hwmon device!\n",
> > +                       __func__);
> > +               return PTR_ERR(hwmon_dev);
> > +       }
> > +
> > +       return 0;
> > +}
> > +
> > +static struct platform_driver nct6694_hwmon_driver = {
> > +       .driver = {
> > +               .name   = DRVNAME,
> > +       },
> > +       .probe          = nct6694_hwmon_probe,
> > +};
> > +
> > +static int __init nct6694_init(void)
> > +{
> > +       int err;
> > +
> > +       err = platform_driver_register(&nct6694_hwmon_driver);
> > +       if (!err) {
> > +               if (err)
> [Kalesh] This whole check looks strange. You can simplify this function as:
> return platform_driver_register(&nct6694_hwmon_driver);
> > +                       platform_driver_unregister(&nct6694_hwmon_driver);
> > +       }
> > +
> > +       return err;
> > +}
> > +subsys_initcall(nct6694_init);
> > +
> > +static void __exit nct6694_exit(void)
> > +{
> > +       platform_driver_unregister(&nct6694_hwmon_driver);
> > +}
> > +module_exit(nct6694_exit);
> > +
> > +MODULE_DESCRIPTION("USB-HWMON driver for NCT6694");
> > +MODULE_AUTHOR("Ming Yu <tmyu0@xxxxxxxxxxx>");
> > +MODULE_LICENSE("GPL");
> > --
> > 2.34.1