Single-channel converters such as mcp3001, mcp3201, mcp3301 and the
upcoming mcp3550/1/3 lack a MOSI pin, so there's no need to call
mcp320x_channel_to_tx_data() for them.
Moreover, instead of calling spi_read() for these converters, which
generates an spi_message and spi_transfer on the stack on every readout,
it's more efficient to use the spi_message and spi_transfer[] included
in struct mcp320x (as we do for multi-channel ADCs), but initialize the
spi_message only with the receive transfer.
Signed-off-by: Lukas Wunner <lukas@xxxxxxxxx>
---
drivers/iio/adc/mcp320x.c | 34 ++++++++++++++--------------------
1 file changed, 14 insertions(+), 20 deletions(-)
diff --git a/drivers/iio/adc/mcp320x.c b/drivers/iio/adc/mcp320x.c
index 49e80b959089..15b5fa7ad427 100644
--- a/drivers/iio/adc/mcp320x.c
+++ b/drivers/iio/adc/mcp320x.c
@@ -78,10 +78,6 @@ static int mcp320x_channel_to_tx_data(int device_index,
int start_bit = 1;
switch (device_index) {
- case mcp3001:
- case mcp3201:
- case mcp3301:
- return 0;
case mcp3002:
case mcp3202:
return ((start_bit << 4) | (!differential << 3) |
@@ -102,20 +98,14 @@ static int mcp320x_adc_conversion(struct mcp320x *adc, u8 channel,
{
int ret;
- adc->rx_buf[0] = 0;
- adc->rx_buf[1] = 0;
- adc->tx_buf = mcp320x_channel_to_tx_data(device_index,
- channel, differential);
+ memset(&adc->rx_buf, 0, sizeof(adc->rx_buf));
+ if (adc->chip_info->num_channels > 1)
+ adc->tx_buf = mcp320x_channel_to_tx_data(device_index, channel,
+ differential);
- if (device_index != mcp3001 && device_index != mcp3201 && device_index != mcp3301) {
- ret = spi_sync(adc->spi, &adc->msg);
- if (ret < 0)
- return ret;
- } else {
- ret = spi_read(adc->spi, &adc->rx_buf, sizeof(adc->rx_buf));
- if (ret < 0)
- return ret;
- }
+ ret = spi_sync(adc->spi, &adc->msg);
+ if (ret < 0)
+ return ret;
switch (device_index) {
case mcp3001:
@@ -329,9 +319,13 @@ static int mcp320x_probe(struct spi_device *spi)
adc->transfer[0].len = sizeof(adc->tx_buf);
adc->transfer[1].rx_buf = adc->rx_buf;
adc->transfer[1].len = sizeof(adc->rx_buf);
-
- spi_message_init_with_transfers(&adc->msg, adc->transfer,
- ARRAY_SIZE(adc->transfer));
+ if (chip_info->num_channels == 1)
+ /* single-channel converters are rx only (no MOSI pin) */
+ spi_message_init_with_transfers(&adc->msg,
+ &adc->transfer[1], 1);
+ else
+ spi_message_init_with_transfers(&adc->msg, adc->transfer,
+ ARRAY_SIZE(adc->transfer));
adc->reg = devm_regulator_get(&spi->dev, "vref");
if (IS_ERR(adc->reg))
--
2.11.0
--
To unsubscribe from this list: send the line "unsubscribe linux-iio" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
