[PATCH v4 1/3] iio: adc: 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 actual wait for new measurement, so to
be sure that read after change is correct functions that changes
datarate and gain will wait for new data.

Fixes: 541880542f2b ("iio: adc: Add TI ADS1100 and ADS1000")
Signed-off-by: Jakub Szczudlo <jakubszczudlo40@xxxxxxxxx>
---
 drivers/iio/adc/ti-ads1100.c | 74 ++++++++++++++++++++++++++++++++++--
 1 file changed, 70 insertions(+), 4 deletions(-)

diff --git a/drivers/iio/adc/ti-ads1100.c b/drivers/iio/adc/ti-ads1100.c
index 9fe8d54cce83..e3c801381434 100644
--- a/drivers/iio/adc/ti-ads1100.c
+++ b/drivers/iio/adc/ti-ads1100.c
@@ -15,6 +15,7 @@
 #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>
@@ -43,6 +44,9 @@
 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 (7.5s) */
+#define ADS1100_MAX_DRDY_TIMEOUT_US	7500000
+
 struct ads1100_data {
 	struct i2c_client *client;
 	struct regulator *reg_vdd;
@@ -123,10 +127,49 @@ static int ads1100_get_adc_result(struct ads1100_data *data, int chan, int *val)
 	return 0;
 }
 
+static bool ads1100_new_data_not_ready(struct ads1100_data *data)
+{
+	int ret;
+	u8 buffer[3];
+
+	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 true;
+	} else if (ret < 3) {
+		dev_err(&data->client->dev, "Short I2C read\n");
+		return true;
+	}
+
+	return FIELD_GET(ADS1100_CFG_ST_BSY, buffer[2]);
+}
+
+static int ads1100_poll_data_ready(struct ads1100_data *data)
+{
+	int ret;
+	u8 buffer[3];
+	bool data_ready;
+	int datarate = ads1100_data_rate[FIELD_GET(ADS1100_DR_MASK, data->config)];
+	/* To be sure we wait 5 times more than datarate */
+	unsigned long wait_time = DIV_ROUND_CLOSEST(MICRO, 5 * datarate);
+
+	/* To be sure that polled value will have value after config change */
+	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 read_poll_timeout(ads1100_new_data_not_ready, data_ready,
+				 !data_ready, wait_time,
+				 ADS1100_MAX_DRDY_TIMEOUT_US, false, data);
+}
+
 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 +178,12 @@ static int ads1100_set_scale(struct ads1100_data *data, int val, int val2)
 	if (!val2)
 		return -EINVAL;
 
+	PM_RUNTIME_ACQUIRE_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
@@ -149,19 +198,36 @@ 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;
+	ret = ads1100_poll_data_ready(data);
+
+	return ret;
 }
 
 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));
+		if (ads1100_data_rate[i] != rate)
+			continue;
+
+		PM_RUNTIME_ACQUIRE_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;
+
+		ret = ads1100_poll_data_ready(data);
+
+		return ret;
 	}
 
 	return -EINVAL;
-- 
2.47.3