Re: [PATCH v3 4/7] iio: pressure: bmp280: Use sleep and forced mode for oneshot captures

[Vasileios Amoiridis]

On Fri, Aug 23, 2024 at 10:25:01PM +0300, Andy Shevchenko wrote:
> On Fri, Aug 23, 2024 at 08:17:11PM +0200, Vasileios Amoiridis wrote:
> > This commit adds forced mode support in sensors BMP28x, BME28x, BMP3xx
> > and BMP58x. Sensors BMP18x and BMP085 are old and do not support this
> > feature so their operation is not affected at all.
> > 
> > Essentially, up to now, the rest of the sensors were used in normal mode
> > all the time. This means that they are continuously doing measurements
> > even though these measurements are not used. Even though the sensor does
> > provide PM support, to cover all the possible use cases, the sensor needs
> > to go into sleep mode and wake up whenever necessary.
> > 
> > This commit, adds sleep and forced mode support. Essentially, the sensor
> > sleeps all the time except for when a measurement is requested. When there
> > is a request for a measurement, the sensor is put into forced mode, starts
> > the measurement and after it is done we read the output and we put it again
> > in sleep mode.
> > 
> > For really fast and more deterministic measurements, the triggered buffer
> > interface can be used, since the sensor is still used in normal mode for
> > that use case.
> > 
> > This commit does not add though support for DEEP STANDBY, Low Power NORMAL
> > and CONTINUOUS modes, supported only by the BMP58x version.
> 
> ...
> 
> > +static const u8 bmp280_operation_mode[] = { BMP280_MODE_SLEEP,
> > +					    BMP280_MODE_FORCED,
> > +					    BMP280_MODE_NORMAL };
> 
> Better style is
> 
> static const u8 bmp280_operation_mode[] = {
> 	BMP280_MODE_SLEEP, BMP280_MODE_FORCED, BMP280_MODE_NORMAL,
> };
> 
> Also note comma at the end.
> 

Looks much better indeed, thanks!

> ...
> 
> > +static int bmp280_wait_conv(struct bmp280_data *data)
> > +{
> > +	unsigned int reg;
> > +	int ret, meas_time;
> > +
> > +	meas_time = BMP280_MEAS_OFFSET;
> > +
> > +	/* Check if we are using a BME280 device */
> > +	if (data->oversampling_humid)
> > +		meas_time += (1 << data->oversampling_humid) * BMP280_MEAS_DUR +
> 
> 		BIT(data->oversampling_humid)

ACK.

> 
> > +			       BMP280_PRESS_HUMID_MEAS_OFFSET;
> 
> > +	/* Pressure measurement time */
> > +	meas_time += (1 << data->oversampling_press) * BMP280_MEAS_DUR +
> 
> Ditto.

ACK.

> 
> > +		      BMP280_PRESS_HUMID_MEAS_OFFSET;
> 
> > +	/* Temperature measurement time */
> > +	meas_time += (1 << data->oversampling_temp) * BMP280_MEAS_DUR;
> 
> Ditto.
> 

ACK.

> > +	usleep_range(meas_time, meas_time * 12 / 10);
> 
> fsleep() ?

Could be used indeed. My concern is that fsleep uses a sleep range
between x and 2x but I don't think it is a problem since these are
oneshot captures.

> 
> > +	ret = regmap_read(data->regmap, BMP280_REG_STATUS, &reg);
> > +	if (ret) {
> > +		dev_err(data->dev, "failed to read status register\n");
> > +		return ret;
> > +	}
> > +	if (reg & BMP280_REG_STATUS_MEAS_BIT) {
> > +		dev_err(data->dev, "Measurement cycle didn't complete\n");
> > +		return -EBUSY;
> > +	}
> > +
> > +	return 0;
> > +}
> 
> ...
> 
> > +static const u8 bmp380_operation_mode[] = { BMP380_MODE_SLEEP,
> > +					    BMP380_MODE_FORCED,
> > +					    BMP380_MODE_NORMAL };
> 
> As per above.
> 

ACK.

> ...
> 
> > +static int bmp380_wait_conv(struct bmp280_data *data)
> > +{
> 
> As per above comments against bmp280_wait_conv().
> 

ACK.

> > +	ret = regmap_read(data->regmap, BMP380_REG_STATUS, &reg);
> > +	if (ret) {
> > +		dev_err(data->dev, "failed to read status register\n");
> > +		return ret;
> > +	}
> 
> > +
> 
> Choose one style (with or without blank line), as in the above you have no
> blank line in the similar situation.
> 

I didn't even notice it, you are right.

> > +	if (!(reg & BMP380_STATUS_DRDY_PRESS_MASK) ||
> > +	    !(reg & BMP380_STATUS_DRDY_TEMP_MASK)) {
> > +		dev_err(data->dev, "Measurement cycle didn't complete.\n");
> > +		return -EBUSY;
> > +	}
> > +
> > +	return 0;
> > +}
> 
> ...
> 
> > +		usleep_range(data->start_up_time, data->start_up_time + 500);
> 
> fsleep() ? Comment?
> 

I could use fsleep(). I didn't add a comment because also before it was
also like this. The code just used hardcoded (2000,2500) while I used
the data->start_up_time. It is mentioned in the datasheet, I could add it.

> ...
> 
> > +static const u8 bmp580_operation_mode[] = { BMP580_MODE_SLEEP,
> > +					    BMP580_MODE_FORCED,
> > +					    BMP580_MODE_NORMAL };
> 
> As per above.
> 

ACK.

> ...
> 
> > +	switch (mode) {
> > +	case BMP280_SLEEP:
> > +		break;
> > +	case BMP280_FORCED:
> > +		ret = regmap_set_bits(data->regmap, BMP580_REG_DSP_CONFIG,
> > +				      BMP580_DSP_IIR_FORCED_FLUSH);
> > +		if (ret) {
> > +			dev_err(data->dev,
> > +				"Could not flush IIR filter constants.\n");
> > +			return ret;
> > +		}
> > +		break;
> > +	case BMP280_NORMAL:
> > +		break;
> 
> Can be unified with _SLEEP case.
> 

ACK.

> > +	default:
> > +		return -EINVAL;
> > +	}
> 
> ...
> 
> > +static int bmp580_wait_conv(struct bmp280_data *data)
> > +{
> > +	/*
> > +	 * Taken from datasheet, Section 2 "Specification, Table 3 "Electrical
> > +	 * characteristics
> 
> Missing period.

ACK.

> 
> > +	 */
> > +	static const int time_conv_press[] = { 0, 1050, 1785, 3045, 5670, 10920, 21420,
> > +					42420, 84420};
> > +	static const int time_conv_temp[] = { 0, 1050, 1105, 1575, 2205, 3465, 6090,
> > +				       11340, 21840};
> 
> Please, start values on the next line after {. Also make }; to be on a separate line.
> 

ACK.

> > +	int meas_time;
> > +
> > +	meas_time = 4000 + time_conv_temp[data->oversampling_temp] +
> > +			   time_conv_press[data->oversampling_press];
> 
> 4 * USEC_PER_MSEC ?

Since the previous values in the arrays are all in thousands, why should
I make this different?

> 
> > +	usleep_range(meas_time, meas_time * 12 / 10);
> 
> Comment? fsleep() ?
> 

The usleep here is for waiting for the sensor to make the conversion,
as the function name points out as well? Should I put it as a comment?

In general, is it considered good practice to add comments above all
sleep functions? I don't think it's a bad idea, I just didn't notice
it somewhere.

> > +	return 0;
> > +}
> 
> ...
> 
> > +	usleep_range(2500, 3000);
> 
> fsleep() ?
> 

ACK.

> -- 
> With Best Regards,
> Andy Shevchenko
> 
> 

Cheers,
Vasilis