From 18215da0c24117da53b164467b89f5dc350b4d0b Mon Sep 17 00:00:00 2001 From: Lukas Wunner Date: Tue, 22 Aug 2017 15:33:00 +0200 Subject: iio: adc: mcp320x: Fix readout of negative voltages commit e6f4794371ee7cce1339e7ca9542f1e703c5f84a upstream. Commit f686a36b4b79 ("iio: adc: mcp320x: Add support for mcp3301") returns a signed voltage from mcp320x_adc_conversion() but neglects that the caller interprets a negative return value as failure. Only mcp3301 (and the upcoming mcp3550/1/3) is affected as the other chips are incapable of measuring negative voltages. Fix and while at it, add mcp3301 to the list of supported chips at the top of the file. Fixes: f686a36b4b79 ("iio: adc: mcp320x: Add support for mcp3301") Cc: Andrea Galbusera Signed-off-by: Lukas Wunner Signed-off-by: Jonathan Cameron Signed-off-by: Greg Kroah-Hartman --- drivers/iio/adc/mcp320x.c | 24 +++++++++++++++--------- 1 file changed, 15 insertions(+), 9 deletions(-) (limited to 'drivers') diff --git a/drivers/iio/adc/mcp320x.c b/drivers/iio/adc/mcp320x.c index 8569c8e1f4b2..5c51f6f5cbff 100644 --- a/drivers/iio/adc/mcp320x.c +++ b/drivers/iio/adc/mcp320x.c @@ -17,6 +17,8 @@ * MCP3204 * MCP3208 * ------------ + * 13 bit converter + * MCP3301 * * Datasheet can be found here: * http://ww1.microchip.com/downloads/en/DeviceDoc/21293C.pdf mcp3001 @@ -96,7 +98,7 @@ static int mcp320x_channel_to_tx_data(int device_index, } static int mcp320x_adc_conversion(struct mcp320x *adc, u8 channel, - bool differential, int device_index) + bool differential, int device_index, int *val) { int ret; @@ -117,19 +119,25 @@ static int mcp320x_adc_conversion(struct mcp320x *adc, u8 channel, switch (device_index) { case mcp3001: - return (adc->rx_buf[0] << 5 | adc->rx_buf[1] >> 3); + *val = (adc->rx_buf[0] << 5 | adc->rx_buf[1] >> 3); + return 0; case mcp3002: case mcp3004: case mcp3008: - return (adc->rx_buf[0] << 2 | adc->rx_buf[1] >> 6); + *val = (adc->rx_buf[0] << 2 | adc->rx_buf[1] >> 6); + return 0; case mcp3201: - return (adc->rx_buf[0] << 7 | adc->rx_buf[1] >> 1); + *val = (adc->rx_buf[0] << 7 | adc->rx_buf[1] >> 1); + return 0; case mcp3202: case mcp3204: case mcp3208: - return (adc->rx_buf[0] << 4 | adc->rx_buf[1] >> 4); + *val = (adc->rx_buf[0] << 4 | adc->rx_buf[1] >> 4); + return 0; case mcp3301: - return sign_extend32((adc->rx_buf[0] & 0x1f) << 8 | adc->rx_buf[1], 12); + *val = sign_extend32((adc->rx_buf[0] & 0x1f) << 8 + | adc->rx_buf[1], 12); + return 0; default: return -EINVAL; } @@ -150,12 +158,10 @@ static int mcp320x_read_raw(struct iio_dev *indio_dev, switch (mask) { case IIO_CHAN_INFO_RAW: ret = mcp320x_adc_conversion(adc, channel->address, - channel->differential, device_index); - + channel->differential, device_index, val); if (ret < 0) goto out; - *val = ret; ret = IIO_VAL_INT; break; -- cgit v1.2.3