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References: <20200616082556.27877-1-lars.povlsen@microchip.com> <20200616082556.27877-4-lars.povlsen@microchip.com> <b44120d8-67fe-4ba3-bc76-80a5a0970dad@roeck-us.net>
From:   Lars Povlsen <lars.povlsen@microchip.com>
To:     Guenter Roeck <linux@roeck-us.net>
CC:     Lars Povlsen <lars.povlsen@microchip.com>,
        Jean Delvare <jdelvare@suse.com>,
        Microchip Linux Driver Support <UNGLinuxDriver@microchip.com>,
        <linux-hwmon@vger.kernel.org>, <devicetree@vger.kernel.org>,
        <linux-arm-kernel@lists.infradead.org>,
        <linux-kernel@vger.kernel.org>,
        Alexandre Belloni <alexandre.belloni@bootlin.com>
Subject: Re: [PATCH v3 3/3] hwmon: sparx5: Add Sparx5 SoC temperature driver
In-Reply-To: <b44120d8-67fe-4ba3-bc76-80a5a0970dad@roeck-us.net>
Date:   Thu, 18 Jun 2020 13:31:24 +0200
Message-ID: <87ftaswqyb.fsf@soft-dev15.microsemi.net>
MIME-Version: 1.0
Content-Type: text/plain
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk


Guenter Roeck writes:

> On 6/16/20 1:25 AM, Lars Povlsen wrote:
>> This patch adds a temperature sensor driver to the Sparx5 SoC.
>>
>> Signed-off-by: Lars Povlsen <lars.povlsen@microchip.com>
>> ---
>>  drivers/hwmon/Kconfig       |  10 +++
>>  drivers/hwmon/Makefile      |   1 +
>>  drivers/hwmon/sparx5-temp.c | 136 ++++++++++++++++++++++++++++++++++++
>
> This will also require documentation in
>         Documentation/hwmon/sparx5-temp.rst
>
>>  3 files changed, 147 insertions(+)
>>  create mode 100644 drivers/hwmon/sparx5-temp.c
>>
>> diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
>> index 288ae9f63588c..7fb5e0c6c6306 100644
>> --- a/drivers/hwmon/Kconfig
>> +++ b/drivers/hwmon/Kconfig
>> @@ -515,6 +515,16 @@ config SENSORS_I5K_AMB
>>         This driver can also be built as a module. If so, the module
>>         will be called i5k_amb.
>>
>> +config SENSORS_SPARX5
>> +     tristate "Sparx5 SoC temperature sensor"
>> +     depends on ARCH_SPARX5 || COMPILE_TEST
>> +     help
>> +       If you say yes here you get support for temperature monitoring
>> +       with the Microchip Sparx5 SoC.
>> +
>> +       This driver can also be built as a module. If so, the module
>> +       will be called sparx5-temp.
>> +
>>  config SENSORS_F71805F
>>       tristate "Fintek F71805F/FG, F71806F/FG and F71872F/FG"
>>       depends on !PPC
>> diff --git a/drivers/hwmon/Makefile b/drivers/hwmon/Makefile
>> index 3e32c21f5efe3..857293f650412 100644
>> --- a/drivers/hwmon/Makefile
>> +++ b/drivers/hwmon/Makefile
>> @@ -167,6 +167,7 @@ obj-$(CONFIG_SENSORS_SMM665)      += smm665.o
>>  obj-$(CONFIG_SENSORS_SMSC47B397)+= smsc47b397.o
>>  obj-$(CONFIG_SENSORS_SMSC47M1)       += smsc47m1.o
>>  obj-$(CONFIG_SENSORS_SMSC47M192)+= smsc47m192.o
>> +obj-$(CONFIG_SENSORS_SPARX5) += sparx5-temp.o
>>  obj-$(CONFIG_SENSORS_STTS751)        += stts751.o
>>  obj-$(CONFIG_SENSORS_AMC6821)        += amc6821.o
>>  obj-$(CONFIG_SENSORS_TC74)   += tc74.o
>> diff --git a/drivers/hwmon/sparx5-temp.c b/drivers/hwmon/sparx5-temp.c
>> new file mode 100644
>> index 0000000000000..4ed8a2aec3ae9
>> --- /dev/null
>> +++ b/drivers/hwmon/sparx5-temp.c
>> @@ -0,0 +1,136 @@
>> +// SPDX-License-Identifier: GPL-2.0-or-later
>> +/* Sparx5 SoC temperature sensor driver
>> + *
>> + * Copyright (C) 2020 Lars Povlsen <lars.povlsen@microchip.com>
>> + */
>> +
>> +#include <linux/module.h>
>> +#include <linux/init.h>
>> +#include <linux/hwmon.h>
>> +#include <linux/io.h>
>> +#include <linux/platform_device.h>
>> +#include <linux/mod_devicetable.h>
>> +#include <linux/bitfield.h>
>
> Alphabetic order, please.

Ack.

>
>> +
>> +#define TEMP_CTRL            0
>> +#define TEMP_CFG             4
>> +#define  TEMP_CFG_CYCLES     GENMASK(24, 15)
>> +#define  TEMP_CFG_ENA                BIT(0)
>> +#define TEMP_STAT            8
>> +#define  TEMP_STAT_VALID     BIT(12)
>> +#define  TEMP_STAT_TEMP              GENMASK(11, 0)
>> +
>> +struct s5_hwmon {
>> +     void __iomem *base;
>> +};
>> +
>> +static void s5_temp_enable(struct s5_hwmon *hwmon)
>> +{
>> +     u32 val = readl(hwmon->base + TEMP_CFG);
>> +     u32 clk = 250;
>> +
>
> Unnecessary variable, and magic number. It would be better to use a define
> or at least explain what the number is for. Also, if this is associated with
> a system clock, would it make sense to use the clock subsystem API to get
> the rate ?
>

Yes, valid point. Changed to reference the system AHB clock, so DT and
bindings updated as well. (The magic number is clock ticks per 1us).

I am sending an update asap.

Thank you for your comments, they are highly appreciated!

Cheers,

---Lars

>> +     val &= ~TEMP_CFG_CYCLES;
>> +     val |= FIELD_PREP(TEMP_CFG_CYCLES, clk);
>> +     val |= TEMP_CFG_ENA;
>> +
>> +     writel(val, hwmon->base + TEMP_CFG);
>> +}
>> +
>> +static int s5_read(struct device *dev, enum hwmon_sensor_types type,
>> +                u32 attr, int channel, long *temp)
>> +{
>> +     struct s5_hwmon *hwmon = dev_get_drvdata(dev);
>> +     int rc = 0, value;
>> +     u32 stat;
>> +
>> +     switch (attr) {
>> +     case hwmon_temp_input:
>> +             stat = readl_relaxed(hwmon->base + TEMP_STAT);
>> +             if (!(stat & TEMP_STAT_VALID))
>> +                     return -EIO;
>> +             value = stat & TEMP_STAT_TEMP;
>> +             value = DIV_ROUND_CLOSEST(value * 3522, 4096) - 1094;
>
> A comment describing the calculation would be useful, not only to help
> the reader but also to help me verify if the calculation is correct
> (especially since datasheets don't seem to be public).
>

I have added the register docs and commented the calculations.

>> +             value *= 100;
>> +             *temp = value;
>> +             break;
>> +     default:
>> +             rc = -EOPNOTSUPP;
>> +             break;
>> +     }
>> +
>> +     return rc;
>> +}
>> +
>> +static umode_t s5_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 struct hwmon_channel_info *s5_info[] = {
>> +     HWMON_CHANNEL_INFO(chip, HWMON_C_REGISTER_TZ),
>> +     HWMON_CHANNEL_INFO(temp, HWMON_T_INPUT),
>> +     NULL
>> +};
>> +
>> +static const struct hwmon_ops s5_hwmon_ops = {
>> +     .is_visible = s5_is_visible,
>> +     .read = s5_read,
>> +};
>> +
>> +static const struct hwmon_chip_info s5_chip_info = {
>> +     .ops = &s5_hwmon_ops,
>> +     .info = s5_info,
>> +};
>> +
>> +static int s5_temp_probe(struct platform_device *pdev)
>> +{
>> +     struct device *hwmon_dev;
>> +     struct s5_hwmon *hwmon;
>> +
>> +     hwmon = devm_kzalloc(&pdev->dev, sizeof(*hwmon), GFP_KERNEL);
>> +     if (!hwmon)
>> +             return -ENOMEM;
>> +
>> +     hwmon->base = devm_platform_ioremap_resource(pdev, 0);
>> +     if (IS_ERR(hwmon->base))
>> +             return PTR_ERR(hwmon->base);
>> +
>> +     s5_temp_enable(hwmon);
>> +
>> +     hwmon_dev = devm_hwmon_device_register_with_info(&pdev->dev,
>> +                                                      "s5_temp",
>> +                                                      hwmon,
>> +                                                      &s5_chip_info,
>> +                                                      NULL);
>> +
>> +     return PTR_ERR_OR_ZERO(hwmon_dev);
>> +}
>> +
>> +const struct of_device_id s5_temp_match[] = {
>> +     { .compatible = "microchip,sparx5-temp" },
>> +     {},
>> +};
>> +MODULE_DEVICE_TABLE(of, s5_temp_match);
>> +
>> +static struct platform_driver s5_temp_driver = {
>> +     .probe = s5_temp_probe,
>> +     .driver = {
>> +             .name = "sparx5-temp",
>> +             .of_match_table = s5_temp_match,
>> +     },
>> +};
>> +
>> +module_platform_driver(s5_temp_driver);
>> +
>> +MODULE_AUTHOR("Lars Povlsen <lars.povlsen@microchip.com>");
>> +MODULE_DESCRIPTION("Sparx5 SoC temperature sensor driver");
>> +MODULE_LICENSE("GPL");
>>

-- 
Lars Povlsen,
Microchip