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| author | Lukas Wunner <lukas@wunner.de> | 2017-09-09 20:32:41 +0200 |
|---|---|---|
| committer | Jonathan Cameron <Jonathan.Cameron@huawei.com> | 2017-09-24 12:34:54 +0100 |
| commit | ea9103186d0508cfbd665a04d2773514e336fa72 (patch) | |
| tree | 4615f9d200ed5426c65cb4cc64a8801ecdda5306 /drivers/iio/adc | |
| parent | f1f065d7ac30ba8b56838271a04501820d190b06 (diff) | |
| download | linux-ea9103186d0508cfbd665a04d2773514e336fa72.tar.gz linux-ea9103186d0508cfbd665a04d2773514e336fa72.tar.bz2 linux-ea9103186d0508cfbd665a04d2773514e336fa72.zip | |
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: Lukas Wunner <lukas@wunner.de>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Diffstat (limited to 'drivers/iio/adc')
| -rw-r--r-- | drivers/iio/adc/mcp320x.c | 34 |
1 files changed, 14 insertions, 20 deletions
diff --git a/drivers/iio/adc/mcp320x.c b/drivers/iio/adc/mcp320x.c index 06bc2453caf9..78a4955d5e2b 100644 --- a/drivers/iio/adc/mcp320x.c +++ b/drivers/iio/adc/mcp320x.c @@ -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; - } + ret = spi_sync(adc->spi, &adc->msg); + if (ret < 0) + return ret; switch (device_index) { case mcp3001: @@ -322,9 +312,13 @@ 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)) |