[PATCH v9 1/3] iio: adc: ti-ads1100: Fix incorrect reading when datarate changed in single mode

[Jakub Szczudlo]

When device is suspended and it is in single mode then changing
datarate doesn't make it actually wait for new measurement, so to
be sure that read after change is correct, functions that changes
datarate and gain will wait for a new data.

Fixes: 541880542f2b ("iio: adc: Add TI ADS1100 and ADS1000")
Signed-off-by: Jakub Szczudlo <jakubszczudlo40@xxxxxxxxx>
---
 drivers/iio/adc/ti-ads1100.c | 108 +++++++++++++++++++++++++++++++++--
 1 file changed, 104 insertions(+), 4 deletions(-)

diff --git a/drivers/iio/adc/ti-ads1100.c b/drivers/iio/adc/ti-ads1100.c
index 9fe8d54cce83..288d209ecf92 100644
--- a/drivers/iio/adc/ti-ads1100.c
+++ b/drivers/iio/adc/ti-ads1100.c
@@ -15,10 +15,12 @@
 #include <linux/module.h>
 #include <linux/init.h>
 #include <linux/i2c.h>
+#include <linux/iopoll.h>
 #include <linux/mutex.h>
 #include <linux/property.h>
 #include <linux/pm_runtime.h>
 #include <linux/regulator/consumer.h>
+#include <linux/time.h>
 #include <linux/units.h>
 
 #include <linux/iio/iio.h>
@@ -43,6 +45,9 @@
 static const int ads1100_data_rate[] = { 128, 32, 16, 8 };
 static const int ads1100_data_rate_bits[] = { 12, 14, 15, 16 };
 
+/* Timeout based on the minimum sample rate of 8 SPS (7500ms) */
+#define ADS1100_MAX_DRDY_TIMEOUT_US	(7500 * USEC_PER_MSEC)
+
 struct ads1100_data {
 	struct i2c_client *client;
 	struct regulator *reg_vdd;
@@ -123,10 +128,87 @@ static int ads1100_get_adc_result(struct ads1100_data *data, int chan, int *val)
 	return 0;
 }
 
+static int ads1100_conversion_busy(struct ads1100_data *data)
+{
+	u8 buffer[3];
+	int ret;
+
+	ret = i2c_master_recv(data->client, (char *)&buffer, sizeof(buffer));
+	if (ret < 0) {
+		dev_err(&data->client->dev, "I2C read fail: %d\n", ret);
+		return ret;
+	}
+
+	return FIELD_GET(ADS1100_CFG_ST_BSY, buffer[2]);
+}
+
+static int ads1100_wait_single_conversion(struct ads1100_data *data)
+{
+	int data_rate_index = FIELD_GET(ADS1100_DR_MASK, data->config);
+	int data_rate_Hz = ads1100_data_rate[data_rate_index];
+	unsigned long poll_us = DIV_ROUND_CLOSEST(USEC_PER_SEC, data_rate_Hz) / 4;
+	int busy;
+	int ret;
+
+	ret = readx_poll_timeout(ads1100_conversion_busy, data,
+				 busy, busy <= 0,
+				 poll_us, ADS1100_MAX_DRDY_TIMEOUT_US);
+	if (busy < 0)
+		return busy;
+
+	return ret;
+}
+
+static int ads1100_start_single_conversion(struct ads1100_data *data)
+{
+	u8 config = data->config | ADS1100_CFG_SC;
+	int ret;
+
+	ret = i2c_master_send(data->client, &config, sizeof(config));
+	if (ret < 0) {
+		dev_err(&data->client->dev, "I2C write fail: %d\n", ret);
+		return ret;
+	}
+   /* Need to wait because of change from continuous to single mode */
+	ret = ads1100_wait_single_conversion(data);
+	if (ret)
+		return ret;
+
+	config |= ADS1100_CFG_ST_BSY;
+
+	ret = i2c_master_send(data->client, &config, sizeof(config));
+	if (ret < 0) {
+		dev_err(&data->client->dev, "I2C write fail: %d\n", ret);
+		return ret;
+	}
+
+	/* No need to cache it, it's status bit */
+	data->config = config & ~ADS1100_CFG_ST_BSY;
+
+	return 0;
+}
+
+static int ads1100_poll_data_ready(struct ads1100_data *data)
+{
+	int ret;
+
+	ret = ads1100_start_single_conversion(data);
+	if (ret)
+		return ret;
+
+	ret = ads1100_wait_single_conversion(data);
+	if (ret)
+		return ret;
+
+	return ads1100_set_config_bits(data, ADS1100_CFG_SC,
+			      ADS1100_CONTINUOUS);
+}
+
 static int ads1100_set_scale(struct ads1100_data *data, int val, int val2)
 {
 	int microvolts;
 	int gain;
+	int ret;
 
 	/* With Vdd between 2.7 and 5V, the scale is always below 1 */
 	if (val)
@@ -135,6 +217,11 @@ static int ads1100_set_scale(struct ads1100_data *data, int val, int val2)
 	if (!val2)
 		return -EINVAL;
 
+	PM_RUNTIME_ACQUIRE_IF_ENABLED_AUTOSUSPEND(&data->client->dev, pm);
+	ret = PM_RUNTIME_ACQUIRE_ERR(&pm);
+	if (ret)
+		return ret;
+
 	microvolts = regulator_get_voltage(data->reg_vdd);
 	/*
 	 * val2 is in 'micro' units, n = val2 / 1000000
@@ -149,22 +236,35 @@ static int ads1100_set_scale(struct ads1100_data *data, int val, int val2)
 
 	ads1100_set_config_bits(data, ADS1100_PGA_MASK, ffs(gain) - 1);
 
-	return 0;
+	return ads1100_poll_data_ready(data);
 }
 
 static int ads1100_set_data_rate(struct ads1100_data *data, int chan, int rate)
 {
 	unsigned int i;
 	unsigned int size;
+	int ret;
 
 	size = data->supports_data_rate ? ARRAY_SIZE(ads1100_data_rate) : 1;
 	for (i = 0; i < size; i++) {
 		if (ads1100_data_rate[i] == rate)
-			return ads1100_set_config_bits(data, ADS1100_DR_MASK,
-						       FIELD_PREP(ADS1100_DR_MASK, i));
+			break;
 	}
 
-	return -EINVAL;
+	if (i == size)
+		return -EINVAL;
+
+	PM_RUNTIME_ACQUIRE_IF_ENABLED_AUTOSUSPEND(&data->client->dev, pm);
+	ret = PM_RUNTIME_ACQUIRE_ERR(&pm);
+	if (ret)
+		return ret;
+
+	ret = ads1100_set_config_bits(data, ADS1100_DR_MASK,
+				      FIELD_PREP(ADS1100_DR_MASK, i));
+	if (ret)
+		return ret;
+
+	return ads1100_poll_data_ready(data);
 }
 
 static int ads1100_get_vdd_millivolts(struct ads1100_data *data)
-- 
2.47.3