[PATCH 4/4] iio: adc: mcp3422: reduce sleep for fast sampling rates

[Mitja Spes <mitja@lxnav.com>]

- reduced sleep time for 240 & 60 sps rates
- minor roundup fix for sleep times

Signed-off-by: Mitja Spes <mitja@lxnav.com>
---
 drivers/iio/adc/mcp3422.c | 16 +++++++++++-----
 1 file changed, 11 insertions(+), 5 deletions(-)

diff --git a/drivers/iio/adc/mcp3422.c b/drivers/iio/adc/mcp3422.c
index eef35fb2fc22..dbcc8fe91aaa 100644
--- a/drivers/iio/adc/mcp3422.c
+++ b/drivers/iio/adc/mcp3422.c
@@ -70,10 +70,11 @@ static const int mcp3422_scales[MCP3422_SRATE_COUNT][MCP3422_PGA_COUNT] = {
 
 /* Constant msleep times for data acquisitions */
 static const int mcp3422_read_times[MCP3422_SRATE_COUNT] = {
-	[MCP3422_SRATE_240] = 1000 / 240,
-	[MCP3422_SRATE_60] = 1000 / 60,
-	[MCP3422_SRATE_15] = 1000 / 15,
-	[MCP3422_SRATE_3] = 1000 / 3 };
+	[MCP3422_SRATE_240] = DIV_ROUND_UP(1000, 240),
+	[MCP3422_SRATE_60] = DIV_ROUND_UP(1000, 60),
+	[MCP3422_SRATE_15] = DIV_ROUND_UP(1000, 15),
+	[MCP3422_SRATE_3] = (100000 + 375 - 100) / 375 /* real rate is 3.75 sps */
+};
 
 /* sample rates to integer conversion table */
 static const int mcp3422_sample_rates[MCP3422_SRATE_COUNT] = {
@@ -137,6 +138,7 @@ static int mcp3422_read_channel(struct mcp3422 *adc,
 				struct iio_chan_spec const *channel, int *value)
 {
 	int ret;
+	int sleep_duration;
 	u8 config;
 	u8 req_channel = channel->channel;
 
@@ -148,7 +150,11 @@ static int mcp3422_read_channel(struct mcp3422 *adc,
 			mutex_unlock(&adc->lock);
 			return ret;
 		}
-		msleep(mcp3422_read_times[MCP3422_SAMPLE_RATE(adc->active_config)]);
+		sleep_duration = mcp3422_read_times[MCP3422_SAMPLE_RATE(adc->active_config)];
+		if (sleep_duration < 20)
+			usleep_range(sleep_duration * 1000, sleep_duration * 1300);
+		else
+			msleep(sleep_duration);
 	}
 
 	ret = mcp3422_read(adc, value, &config);
-- 
2.34.1