linux-kernel - Re: [PATCH v2 2/3] iio: dps310: Temperature measurement errata

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Date:   Thu, 9 May 2019 10:17:14 -0500
From:   Eddie James <eajames@...ux.vnet.ibm.com>
To:     Matt Ranostay <matt.ranostay@...sulko.com>,
        Eddie James <eajames@...ux.ibm.com>
Cc:     "open list:IIO SUBSYSTEM AND DRIVERS" <linux-iio@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>, joel@....id.au,
        Peter Meerwald-Stadler <pmeerw@...erw.net>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Hartmut Knaack <knaack.h@....de>,
        Jonathan Cameron <jic23@...nel.org>,
        Christopher Bostic <cbostic@...ux.vnet.ibm.com>
Subject: Re: [PATCH v2 2/3] iio: dps310: Temperature measurement errata


On 5/8/19 10:09 PM, Matt Ranostay wrote:
> On Thu, May 9, 2019 at 3:36 AM Eddie James <eajames@...ux.ibm.com> wrote:
>> From: Christopher Bostic <cbostic@...ux.vnet.ibm.com>
>>
>> Add a manufacturer's suggested workaround to deal with early revisions
>> of chip that don't indicate correct temperature. Readings can be in the
>> ~60C range when they should be in the ~20's.
>>
>> Signed-off-by: Christopher Bostic <cbostic@...ux.vnet.ibm.com>
>> Signed-off-by: Joel Stanley <joel@....id.au>
>> Signed-off-by: Eddie James <eajames@...ux.ibm.com>
>> ---
>>   drivers/iio/pressure/dps310.c | 51 ++++++++++++++++++++++++++++++++++++++++++-
>>   1 file changed, 50 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/iio/pressure/dps310.c b/drivers/iio/pressure/dps310.c
>> index 7afaa88..c42808e 100644
>> --- a/drivers/iio/pressure/dps310.c
>> +++ b/drivers/iio/pressure/dps310.c
>> @@ -221,6 +221,9 @@ static bool dps310_is_writeable_reg(struct device *dev, unsigned int reg)
>>          case DPS310_MEAS_CFG:
>>          case DPS310_CFG_REG:
>>          case DPS310_RESET:
>> +       case 0x0e:
>> +       case 0x0f:
>> +       case 0x62:
> What is with the magic values? Are they not documented to what they
> are, and hence not defining enum values for them?
>
> - Matt


Thats correct. These don't show up in the data sheet so I left them as 
raw values. Chris, do you know what the source for these values was?

Thanks,

Eddie


>
>>                  return true;
>>          default:
>>                  return false;
>> @@ -237,6 +240,7 @@ static bool dps310_is_volatile_reg(struct device *dev, unsigned int reg)
>>          case DPS310_TMP_B1:
>>          case DPS310_TMP_B2:
>>          case DPS310_MEAS_CFG:
>> +       case 0x32:
>>                  return true;
>>          default:
>>                  return false;
>> @@ -314,7 +318,7 @@ static int dps310_read_raw(struct iio_dev *iio,
>>          .writeable_reg = dps310_is_writeable_reg,
>>          .volatile_reg = dps310_is_volatile_reg,
>>          .cache_type = REGCACHE_RBTREE,
>> -       .max_register = 0x29,
>> +       .max_register = 0x62,
>>   };
>>
>>   static const struct iio_info dps310_info = {
>> @@ -322,6 +326,47 @@ static int dps310_read_raw(struct iio_dev *iio,
>>          .write_raw = dps310_write_raw,
>>   };
>>
>> +/*
>> + * Some verions of chip will read temperatures in the ~60C range when
>> + * its actually ~20C. This is the manufacturer recommended workaround
>> + * to correct the issue.
>> + */
>> +static int dps310_temp_workaround(struct dps310_data *data)
>> +{
>> +       int r, reg;
>> +
>> +       r = regmap_read(data->regmap, 0x32, &reg);
>> +       if (r < 0)
>> +               return r;
>> +
>> +       /*
>> +        * If bit 1 is set then the device is okay, and the workaround does not
>> +        * need to be applied
>> +        */
>> +       if (reg & BIT(1))
>> +               return 0;
>> +
>> +       r = regmap_write(data->regmap, 0x0e, 0xA5);
>> +       if (r < 0)
>> +               return r;
>> +
>> +       r = regmap_write(data->regmap, 0x0f, 0x96);
>> +       if (r < 0)
>> +               return r;
>> +
>> +       r = regmap_write(data->regmap, 0x62, 0x02);
>> +       if (r < 0)
>> +               return r;
>> +
>> +       r = regmap_write(data->regmap, 0x0e, 0x00);
>> +       if (r < 0)
>> +               return r;
>> +
>> +       r = regmap_write(data->regmap, 0x0f, 0x00);
>> +
>> +       return r;
>> +}
>> +
>>   static int dps310_probe(struct i2c_client *client,
>>                          const struct i2c_device_id *id)
>>   {
>> @@ -383,6 +428,10 @@ static int dps310_probe(struct i2c_client *client,
>>          if (r < 0)
>>                  goto err;
>>
>> +       r = dps310_temp_workaround(data);
>> +       if (r < 0)
>> +               return r;
>> +
>>          r = devm_iio_device_register(&client->dev, iio);
>>          if (r)
>>                  goto err;
>> --
>> 1.8.3.1
>>