Commit ea910318 authored by Lukas Wunner's avatar Lukas Wunner Committed by Jonathan Cameron
Browse files

iio: adc: mcp320x: Speed up readout of single-channel ADCs 



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: default avatarLukas Wunner <lukas@wunner.de>
Signed-off-by: default avatarJonathan Cameron <Jonathan.Cameron@huawei.com>
parent f1f065d7

drivers/iio/adc/mcp320x.c

+14 −20
Original line number Diff line number Diff line
@@ -76,10 +76,6 @@ 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) |
@@ -100,20 +96,14 @@ 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;

	}



	switch (device_index) {

	case mcp3001:
@@ -322,7 +312,11 @@ 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);



	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));