Re: [PATCH 1/2] hwmon: Add Synaptics AS370 PVT sensor driver

[Jisheng Zhang <Jisheng.Zhang@synaptics.com>]

Hi Guenter,

On Mon, 26 Aug 2019 06:44:34 -0700 Guenter Roeck wrote:

> 
> 
> On 8/26/19 3:01 AM, Jisheng Zhang wrote:
> > Add a new driver for Synaptics AS370 PVT sensors. Currently, only
> > temperature is supported.
> >
> > Signed-off-by: Jisheng Zhang <Jisheng.Zhang@synaptics.com>
> > ---
> >   drivers/hwmon/Kconfig       |  10 +++
> >   drivers/hwmon/Makefile      |   1 +
> >   drivers/hwmon/as370-hwmon.c | 158 ++++++++++++++++++++++++++++++++++++
> >   3 files changed, 169 insertions(+)
> >   create mode 100644 drivers/hwmon/as370-hwmon.c
> >
> > diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
> > index 650dd71f9724..d31610933faa 100644
> > --- a/drivers/hwmon/Kconfig
> > +++ b/drivers/hwmon/Kconfig
> > @@ -246,6 +246,16 @@ config SENSORS_ADT7475
> >         This driver can also be built as a module. If so, the module
> >         will be called adt7475.
> >
> > +config SENSORS_AS370
> > +     tristate "Synaptics AS370 SoC hardware monitoring driver"  
> 
> I think this needs "depends on HAS_IOMEM".

HWMON depends on HAS_IOMEM, so the dependency has been required
by the common HWMON, we don't need it here.

> 
> > +     help
> > +       If you say yes here you get support for the PVT sensors of
> > +       the Synaptics AS370 SoC
> > +
> > +       This driver can also be built as a module. If so, the module
> > +       will be called as370-hwmon.
> > +
> > +
> >   config SENSORS_ASC7621
> >       tristate "Andigilog aSC7621"
> >       depends on I2C
> > diff --git a/drivers/hwmon/Makefile b/drivers/hwmon/Makefile
> > index 8db472ea04f0..252e8a4c9781 100644
> > --- a/drivers/hwmon/Makefile
> > +++ b/drivers/hwmon/Makefile
> > @@ -48,6 +48,7 @@ obj-$(CONFIG_SENSORS_ADT7475)       += adt7475.o
> >   obj-$(CONFIG_SENSORS_APPLESMC)      += applesmc.o
> >   obj-$(CONFIG_SENSORS_ARM_SCMI)      += scmi-hwmon.o
> >   obj-$(CONFIG_SENSORS_ARM_SCPI)      += scpi-hwmon.o
> > +obj-$(CONFIG_SENSORS_AS370)  += as370-hwmon.o
> >   obj-$(CONFIG_SENSORS_ASC7621)       += asc7621.o
> >   obj-$(CONFIG_SENSORS_ASPEED)        += aspeed-pwm-tacho.o
> >   obj-$(CONFIG_SENSORS_ATXP1) += atxp1.o
> > diff --git a/drivers/hwmon/as370-hwmon.c b/drivers/hwmon/as370-hwmon.c
> > new file mode 100644
> > index 000000000000..98dfba45e1b0
> > --- /dev/null
> > +++ b/drivers/hwmon/as370-hwmon.c
> > @@ -0,0 +1,158 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +/*
> > + * Synaptics AS370 SoC Hardware Monitoring Driver
> > + *
> > + * Copyright (C) 2018 Synaptics Incorporated
> > + * Author: Jisheng Zhang <jszhang@kernel.org>
> > + */
> > +
> > +#include <linux/bitops.h>
> > +#include <linux/delay.h>  
> 
> Unnecessary include file.

will remove it in newer version.

> 
> > +#include <linux/hwmon.h>
> > +#include <linux/init.h>
> > +#include <linux/io.h>
> > +#include <linux/module.h>
> > +#include <linux/of_device.h>
> > +
> > +#define CTRL         0x0
> > +#define  PD          BIT(0)
> > +#define  EN          BIT(1)
> > +#define  T_SEL               BIT(2)
> > +#define  V_SEL               BIT(3)
> > +#define  NMOS_SEL    BIT(8)
> > +#define  PMOS_SEL    BIT(9)
> > +#define STS          0x4
> > +#define  BN_MASK     (0xfff << 0)  
> 
> How about using GENMASK() ?

Good idea.

> 
> > +#define  EOC         BIT(12)
> > +
> > +struct as370_hwmon {
> > +     void __iomem *base;
> > +};
> > +
> > +static void init_pvt(struct as370_hwmon *hwmon)
> > +{
> > +     u32 val;
> > +     void __iomem *addr = hwmon->base + CTRL;
> > +
> > +     val = PD;
> > +     writel_relaxed(val, addr);
> > +     val |= T_SEL;
> > +     val &= ~V_SEL;
> > +     val &= ~NMOS_SEL;
> > +     val &= ~PMOS_SEL;  
> 
> What is the point of this ? We know that val == PD here.

yes, could be removed

> 
> > +     writel_relaxed(val, addr);
> > +     val |= EN;
> > +     writel_relaxed(val, addr);
> > +     val &= ~PD;
> > +     writel_relaxed(val, addr);
> > +}
> > +
> > +static int read_pvt(struct as370_hwmon *hwmon)
> > +{
> > +     return readl_relaxed(hwmon->base + STS) & BN_MASK;
> > +}  
> 
> Please fold into the calling code.
> 
> > +
> > +static int as370_hwmon_read(struct device *dev, enum hwmon_sensor_types type,
> > +                         u32 attr, int channel, long *temp)
> > +{
> > +     int val;
> > +     struct as370_hwmon *hwmon = dev_get_drvdata(dev);
> > +
> > +     switch (attr) {
> > +     case hwmon_temp_input:
> > +             val = read_pvt(hwmon);
> > +             if (val < 0)
> > +                     return val;  
> 
> read_pvt() doesn't return a negative error code. This check is unnecessary.
> 
> > +             *temp = val * 251802 / 4096 - 85525;  
> 
> This results in rounding down the reported temperature. It is ok if it is
> what you want; otherwise, I would suggest to use DIV_ROUND_CLOSEST().

Good idea.

Thanks for your review,
Jisheng

> 
> > +             break;
> > +     default:
> > +             return -EOPNOTSUPP;
> > +     }
> > +
> > +     return 0;
> > +}
> > +
> > +static umode_t
> > +as370_hwmon_is_visible(const void *data, enum hwmon_sensor_types type,
> > +                    u32 attr, int channel)
> > +{
> > +     if (type != hwmon_temp)
> > +             return 0;
> > +
> > +     switch (attr) {
> > +     case hwmon_temp_input:
> > +             return 0444;
> > +     default:
> > +             return 0;
> > +     }
> > +}
> > +
> > +static const u32 as370_hwmon_temp_config[] = {
> > +     HWMON_T_INPUT,
> > +     0
> > +};
> > +
> > +static const struct hwmon_channel_info as370_hwmon_temp = {
> > +     .type = hwmon_temp,
> > +     .config = as370_hwmon_temp_config,
> > +};
> > +
> > +static const struct hwmon_channel_info *as370_hwmon_info[] = {
> > +     &as370_hwmon_temp,
> > +     NULL
> > +};
> > +
> > +static const struct hwmon_ops as370_hwmon_ops = {
> > +     .is_visible = as370_hwmon_is_visible,
> > +     .read = as370_hwmon_read,
> > +};
> > +
> > +static const struct hwmon_chip_info as370_chip_info = {
> > +     .ops = &as370_hwmon_ops,
> > +     .info = as370_hwmon_info,
> > +};
> > +
> > +static int as370_hwmon_probe(struct platform_device *pdev)
> > +{
> > +     struct resource *res;
> > +     struct device *hwmon_dev;
> > +     struct as370_hwmon *hwmon;
> > +     struct device *dev = &pdev->dev;
> > +
> > +     hwmon = devm_kzalloc(dev, sizeof(*hwmon), GFP_KERNEL);
> > +     if (!hwmon)
> > +             return -ENOMEM;
> > +
> > +     res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> > +     hwmon->base = devm_ioremap_resource(&pdev->dev, res);
> > +     if (IS_ERR(hwmon->base))
> > +             return PTR_ERR(hwmon->base);
> > +
> > +     init_pvt(hwmon);
> > +
> > +     hwmon_dev = devm_hwmon_device_register_with_info(dev,
> > +                                                      "as370_hwmon",  
> 
> The "_hwmon" seems unnecessary. It will show up in "sensors" as part
> of the sensor name. Is this really what you want ?
> 
> > +                                                      hwmon,
> > +                                                      &as370_chip_info,
> > +                                                      NULL);
> > +     return PTR_ERR_OR_ZERO(hwmon_dev);
> > +}
> > +
> > +static const struct of_device_id as370_hwmon_match[] = {
> > +     { .compatible = "syna,as370-hwmon" },
> > +     {},
> > +};
> > +MODULE_DEVICE_TABLE(of, as370_hwmon_match);
> > +
> > +static struct platform_driver as370_hwmon_driver = {
> > +     .probe = as370_hwmon_probe,
> > +     .driver = {
> > +             .name = "as370-hwmon",
> > +             .of_match_table = as370_hwmon_match,
> > +     },
> > +};
> > +module_platform_driver(as370_hwmon_driver);
> > +
> > +MODULE_AUTHOR("Jisheng Zhang<jszhang@kernel.org>");
> > +MODULE_DESCRIPTION("Synaptics AS370 SoC hardware monitor");
> > +MODULE_LICENSE("GPL v2");
> >  
>