Date:   Fri, 19 Aug 2016 10:57:33 +0200
From:   Mike Looijmans <mike.looijmans@...ic.nl>
To:     Guenter Roeck <linux@...ck-us.net>, hjk@...sjkoch.de
Cc:     linux-hwmon@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4] hwmon: (max6650.c) Add devicetree support

(resent through different SMTP server, bounced as spam because of company 
server's unwanted modifications, sorry if you received this twice now)

On 19-08-16 04:43, Guenter Roeck wrote:
> On 08/16/2016 12:20 AM, Mike Looijmans wrote:
>> Parse devicetree parameters for voltage and prescaler setting. This allows
>> using multiple max6550 devices with varying settings, and also makes it
>> possible to instantiate and configure the device using devicetree.
>>
>> Signed-off-by: Mike Looijmans <mike.looijmans@...ic.nl>
>> ---
>> v4: Vendor prefix "maxim," for devicetree properties and compatible string
>>     Split documentation into separate patch
>> v3: Resubmit because wrong mailing lists used
>>     Fix style errors as reported by checkpatch.pl
>>     Fix bug in DT parsing of fan-prescale
>> v2: Add devicetree binding documentation
>>     Code changes as suggested by Guenter
>>     Reduce log info, output only a single line
>>  drivers/hwmon/max6650.c | 47 ++++++++++++++++++++++++++++++++++++-----------
>>  1 file changed, 36 insertions(+), 11 deletions(-)
>>
>> diff --git a/drivers/hwmon/max6650.c b/drivers/hwmon/max6650.c
>> index 162a520..6beb62c 100644
>> --- a/drivers/hwmon/max6650.c
>> +++ b/drivers/hwmon/max6650.c
>> @@ -39,6 +39,7 @@
>>  #include <linux/hwmon.h>
>>  #include <linux/hwmon-sysfs.h>
>>  #include <linux/err.h>
>> +#include <linux/of_device.h>
>>
>>  /*
>>   * Insmod parameters
>> @@ -48,7 +49,7 @@
>>  static int fan_voltage;
>>  /* prescaler: Possible values are 1, 2, 4, 8, 16 or 0 for don't change */
>>  static int prescaler;
>> -/* clock: The clock frequency of the chip the driver should assume */
>> +/* clock: The clock frequency of the chip (max6651 can be clocked
>> externally) */
>>  static int clock = 254000;
>>
>>  module_param(fan_voltage, int, S_IRUGO);
>> @@ -133,6 +134,19 @@ static const u8 tach_reg[] = {
>>      MAX6650_REG_TACH3,
>>  };
>>
>> +static const struct of_device_id max6650_dt_match[] = {
>> +    {
>> +        .compatible = "maxim,max6650",
>> +        .data = (void *)1
>> +    },
>> +    {
>> +        .compatible = "maxim,max6651",
>> +        .data = (void *)4
>> +    },
>> +    { },
>> +};
>> +MODULE_DEVICE_TABLE(of, max6650_dt_match);
>> +
>>  static struct max6650_data *max6650_update_device(struct device *dev)
>>  {
>>      struct max6650_data *data = dev_get_drvdata(dev);
>> @@ -566,6 +580,17 @@ static int max6650_init_client(struct max6650_data *data,
>>      struct device *dev = &client->dev;
>>      int config;
>>      int err = -EIO;
>> +    u32 voltage;
>> +    u32 prescale;
>> +
>> +    if (of_property_read_u32(dev->of_node, "maxim,fan-microvolt",
>> +                 &voltage))
>> +        voltage = fan_voltage;
>> +    else
>> +        voltage = voltage > 5500000 ? 12 : 5;
>
> I think this should only accept 5V or 12V.
>
> Guenter

A 4V, 10V or 13V fan will also work just fine, the voltage register just sets 
the range of the feedback tachometer.

I don't have strong feelings either way, so if you feel the drive should bail 
out on anything but 5 or 12, that's fine with me too.

Should I change this and send a v5 patch?



>> +    if (of_property_read_u32(dev->of_node, "maxim,fan-prescale",
>> +                 &prescale))
>> +        prescale = prescaler;
>>
>>      config = i2c_smbus_read_byte_data(client, MAX6650_REG_CONFIG);
>>
>> @@ -574,7 +599,7 @@ static int max6650_init_client(struct max6650_data *data,
>>          return err;
>>      }
>>
>> -    switch (fan_voltage) {
>> +    switch (voltage) {
>>      case 0:
>>          break;
>>      case 5:
>> @@ -584,14 +609,10 @@ static int max6650_init_client(struct max6650_data *data,
>>          config |= MAX6650_CFG_V12;
>>          break;
>>      default:
>> -        dev_err(dev, "illegal value for fan_voltage (%d)\n",
>> -            fan_voltage);
>> +        dev_err(dev, "illegal value for fan_voltage (%d)\n", voltage);
>>      }
>>
>> -    dev_info(dev, "Fan voltage is set to %dV.\n",
>> -         (config & MAX6650_CFG_V12) ? 12 : 5);
>> -
>> -    switch (prescaler) {
>> +    switch (prescale) {
>>      case 0:
>>          break;
>>      case 1:
>> @@ -614,10 +635,11 @@ static int max6650_init_client(struct max6650_data *data,
>>               | MAX6650_CFG_PRESCALER_16;
>>          break;
>>      default:
>> -        dev_err(dev, "illegal value for prescaler (%d)\n", prescaler);
>> +        dev_err(dev, "illegal value for prescaler (%d)\n", prescale);
>>      }
>>
>> -    dev_info(dev, "Prescaler is set to %d.\n",
>> +    dev_info(dev, "Fan voltage: %dV, prescaler: %d.\n",
>> +         (config & MAX6650_CFG_V12) ? 12 : 5,
>>           1 << (config & MAX6650_CFG_PRESCALER_MASK));
>>
>>      /*
>> @@ -651,6 +673,8 @@ static int max6650_probe(struct i2c_client *client,
>>               const struct i2c_device_id *id)
>>  {
>>      struct device *dev = &client->dev;
>> +    const struct of_device_id *of_id =
>> +        of_match_device(of_match_ptr(max6650_dt_match), dev);
>>      struct max6650_data *data;
>>      struct device *hwmon_dev;
>>      int err;
>> @@ -661,7 +685,7 @@ static int max6650_probe(struct i2c_client *client,
>>
>>      data->client = client;
>>      mutex_init(&data->update_lock);
>> -    data->nr_fans = id->driver_data;
>> +    data->nr_fans = of_id ? (int)(uintptr_t)of_id->data : id->driver_data;
>>
>>      /*
>>       * Initialize the max6650 chip
>> @@ -691,6 +715,7 @@ MODULE_DEVICE_TABLE(i2c, max6650_id);
>>  static struct i2c_driver max6650_driver = {
>>      .driver = {
>>          .name    = "max6650",
>> +        .of_match_table = of_match_ptr(max6650_dt_match),
>>      },
>>      .probe        = max6650_probe,
>>      .id_table    = max6650_id,
>>
>

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