Re: [RESEND PATCH v3 2/3] iio: chemical: Add support for external Reset and Wakeup in CCS811

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On Tue, Apr 14, 2020 at 9:49 PM <mani@xxxxxxxxxx> wrote:
>
> From: Manivannan Sadhasivam <mani@xxxxxxxxxx>
>
> CCS811 VOC sensor exposes nRESET and nWAKE pins which can be connected
> to GPIO pins of the host controller. These pins can be used to externally
> release the device from reset and also to wake it up before any I2C
> transaction. The initial driver support assumed that the nRESET pin is not
> connected and the nWAKE pin is tied to ground.
>
> This commit improves it by adding support for controlling those two pins
> externally using a host controller. For the case of reset, if the hardware
> reset is not available, the mechanism to do software reset is also added.
>
> As a side effect of doing this, the IIO device allocation needs to be
> slightly moved to top of probe to make use of priv data early.
>

LGTM,
Reviewed-by: Andy Shevchenko <andy.shevchenko@xxxxxxxxx>

> Signed-off-by: Manivannan Sadhasivam <mani@xxxxxxxxxx>
> ---
>  drivers/iio/chemical/ccs811.c | 105 ++++++++++++++++++++++++++++++----
>  1 file changed, 94 insertions(+), 11 deletions(-)
>
> diff --git a/drivers/iio/chemical/ccs811.c b/drivers/iio/chemical/ccs811.c
> index 2ebdfc35bcda..1500e4b0dfbd 100644
> --- a/drivers/iio/chemical/ccs811.c
> +++ b/drivers/iio/chemical/ccs811.c
> @@ -16,6 +16,7 @@
>   */
>
>  #include <linux/delay.h>
> +#include <linux/gpio/consumer.h>
>  #include <linux/i2c.h>
>  #include <linux/iio/iio.h>
>  #include <linux/iio/buffer.h>
> @@ -36,6 +37,7 @@
>  #define CCS811_ERR             0xE0
>  /* Used to transition from boot to application mode */
>  #define CCS811_APP_START       0xF4
> +#define CCS811_SW_RESET                0xFF
>
>  /* Status register flags */
>  #define CCS811_STATUS_ERROR            BIT(0)
> @@ -74,6 +76,7 @@ struct ccs811_data {
>         struct mutex lock; /* Protect readings */
>         struct ccs811_reading buffer;
>         struct iio_trigger *drdy_trig;
> +       struct gpio_desc *wakeup_gpio;
>         bool drdy_trig_on;
>  };
>
> @@ -166,10 +169,25 @@ static int ccs811_setup(struct i2c_client *client)
>                                          CCS811_MODE_IAQ_1SEC);
>  }
>
> +static void ccs811_set_wakeup(struct ccs811_data *data, bool enable)
> +{
> +       if (!data->wakeup_gpio)
> +               return;
> +
> +       gpiod_set_value(data->wakeup_gpio, enable);
> +
> +       if (enable)
> +               usleep_range(50, 60);
> +       else
> +               usleep_range(20, 30);
> +}
> +
>  static int ccs811_get_measurement(struct ccs811_data *data)
>  {
>         int ret, tries = 11;
>
> +       ccs811_set_wakeup(data, true);
> +
>         /* Maximum waiting time: 1s, as measurements are made every second */
>         while (tries-- > 0) {
>                 ret = i2c_smbus_read_byte_data(data->client, CCS811_STATUS);
> @@ -183,9 +201,12 @@ static int ccs811_get_measurement(struct ccs811_data *data)
>         if (!(ret & CCS811_STATUS_DATA_READY))
>                 return -EIO;
>
> -       return i2c_smbus_read_i2c_block_data(data->client,
> +       ret = i2c_smbus_read_i2c_block_data(data->client,
>                                             CCS811_ALG_RESULT_DATA, 8,
>                                             (char *)&data->buffer);
> +       ccs811_set_wakeup(data, false);
> +
> +       return ret;
>  }
>
>  static int ccs811_read_raw(struct iio_dev *indio_dev,
> @@ -336,6 +357,45 @@ static irqreturn_t ccs811_data_rdy_trigger_poll(int irq, void *private)
>         return IRQ_HANDLED;
>  }
>
> +static int ccs811_reset(struct i2c_client *client)
> +{
> +       struct gpio_desc *reset_gpio;
> +       int ret;
> +
> +       reset_gpio = devm_gpiod_get_optional(&client->dev, "reset",
> +                                            GPIOD_OUT_LOW);
> +       if (IS_ERR(reset_gpio))
> +               return PTR_ERR(reset_gpio);
> +
> +       /* Try to reset using nRESET pin if available else do SW reset */
> +       if (reset_gpio) {
> +               gpiod_set_value(reset_gpio, 1);
> +               usleep_range(20, 30);
> +               gpiod_set_value(reset_gpio, 0);
> +       } else {
> +               /*
> +                * As per the datasheet, this sequence of values needs to be
> +                * written to the SW_RESET register for triggering the soft
> +                * reset in the device and placing it in boot mode.
> +                */
> +               static const u8 reset_seq[] = {
> +                       0x11, 0xE5, 0x72, 0x8A,
> +               };
> +
> +               ret = i2c_smbus_write_i2c_block_data(client, CCS811_SW_RESET,
> +                                            sizeof(reset_seq), reset_seq);
> +               if (ret < 0) {
> +                       dev_err(&client->dev, "Failed to reset sensor\n");
> +                       return ret;
> +               }
> +       }
> +
> +       /* tSTART delay required after reset */
> +       usleep_range(1000, 2000);
> +
> +       return 0;
> +}
> +
>  static int ccs811_probe(struct i2c_client *client,
>                         const struct i2c_device_id *id)
>  {
> @@ -348,36 +408,59 @@ static int ccs811_probe(struct i2c_client *client,
>                                      | I2C_FUNC_SMBUS_READ_I2C_BLOCK))
>                 return -EOPNOTSUPP;
>
> +       indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*data));
> +       if (!indio_dev)
> +               return -ENOMEM;
> +
> +       data = iio_priv(indio_dev);
> +       i2c_set_clientdata(client, indio_dev);
> +       data->client = client;
> +
> +       data->wakeup_gpio = devm_gpiod_get_optional(&client->dev, "wakeup",
> +                                                   GPIOD_OUT_HIGH);
> +       if (IS_ERR(data->wakeup_gpio))
> +               return PTR_ERR(data->wakeup_gpio);
> +
> +       ccs811_set_wakeup(data, true);
> +
> +       ret = ccs811_reset(client);
> +       if (ret) {
> +               ccs811_set_wakeup(data, false);
> +               return ret;
> +       }
> +
>         /* Check hardware id (should be 0x81 for this family of devices) */
>         ret = i2c_smbus_read_byte_data(client, CCS811_HW_ID);
> -       if (ret < 0)
> +       if (ret < 0) {
> +               ccs811_set_wakeup(data, false);
>                 return ret;
> +       }
>
>         if (ret != CCS811_HW_ID_VALUE) {
>                 dev_err(&client->dev, "hardware id doesn't match CCS81x\n");
> +               ccs811_set_wakeup(data, false);
>                 return -ENODEV;
>         }
>
>         ret = i2c_smbus_read_byte_data(client, CCS811_HW_VERSION);
> -       if (ret < 0)
> +       if (ret < 0) {
> +               ccs811_set_wakeup(data, false);
>                 return ret;
> +       }
>
>         if ((ret & CCS811_HW_VERSION_MASK) != CCS811_HW_VERSION_VALUE) {
>                 dev_err(&client->dev, "no CCS811 sensor\n");
> +               ccs811_set_wakeup(data, false);
>                 return -ENODEV;
>         }
>
> -       indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*data));
> -       if (!indio_dev)
> -               return -ENOMEM;
> -
>         ret = ccs811_setup(client);
> -       if (ret < 0)
> +       if (ret < 0) {
> +               ccs811_set_wakeup(data, false);
>                 return ret;
> +       }
>
> -       data = iio_priv(indio_dev);
> -       i2c_set_clientdata(client, indio_dev);
> -       data->client = client;
> +       ccs811_set_wakeup(data, false);
>
>         mutex_init(&data->lock);
>
> --
> 2.17.1
>


-- 
With Best Regards,
Andy Shevchenko



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