iio: adc: ti-ads1015: add adequate wait time to get correct conversion (4744d4e2) · Commits · 戴 / test

This driver assumes that the device is operating in the continuous conversion mode which performs the conversion continuously. So this driver inserts a wait time before reading the conversion register if the configuration is changed from a previous request. Currently, the wait time is only the period required for a single conversion that is calculated as the reciprocal of the sampling frequency. However we also need to wait for the the previous conversion to complete. Otherwise we probably get the conversion result for the previous configuration when the sampling frequency is lower. Cc: Daniel Baluta <daniel.baluta@gmail.com> Signed-off-by:

Akinobu Mita <akinobu.mita@gmail.com> Cc: <Stable@vger.kernel.org> Signed-off-by:

Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/adc/ti-ads1015.c

+19 −12

Original line number	Diff line number	Diff line
		@@ -242,27 +242,34 @@ static
		int ads1015_get_adc_result(struct ads1015_data data, int chan, int val)
		{
		int ret, pga, dr, conv_time;
		bool change;
		unsigned int old, mask, cfg;

		if (chan < 0 \|\| chan >= ADS1015_CHANNELS)
		return -EINVAL;

		ret = regmap_read(data->regmap, ADS1015_CFG_REG, &old);
		if (ret)
		return ret;

		pga = data->channel_data[chan].pga;
		dr = data->channel_data[chan].data_rate;
		mask = ADS1015_CFG_MUX_MASK \| ADS1015_CFG_PGA_MASK \|
		ADS1015_CFG_DR_MASK;
		cfg = chan << ADS1015_CFG_MUX_SHIFT \| pga << ADS1015_CFG_PGA_SHIFT \|
		dr << ADS1015_CFG_DR_SHIFT;

		ret = regmap_update_bits_check(data->regmap, ADS1015_CFG_REG,
		ADS1015_CFG_MUX_MASK \|
		ADS1015_CFG_PGA_MASK \|
		ADS1015_CFG_DR_MASK,
		chan << ADS1015_CFG_MUX_SHIFT \|
		pga << ADS1015_CFG_PGA_SHIFT \|
		dr << ADS1015_CFG_DR_SHIFT,
		&change);
		if (ret < 0)
		cfg = (old & ~mask) \| (cfg & mask);

		ret = regmap_write(data->regmap, ADS1015_CFG_REG, cfg);
		if (ret)
		return ret;

		if (change \|\| data->conv_invalid) {
		conv_time = DIV_ROUND_UP(USEC_PER_SEC, data->data_rate[dr]);
		if (old != cfg \|\| data->conv_invalid) {
		int dr_old = (old & ADS1015_CFG_DR_MASK) >>
		ADS1015_CFG_DR_SHIFT;

		conv_time = DIV_ROUND_UP(USEC_PER_SEC, data->data_rate[dr_old]);
		conv_time += DIV_ROUND_UP(USEC_PER_SEC, data->data_rate[dr]);
		usleep_range(conv_time, conv_time + 1);
		data->conv_invalid = false;
		}

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