On Sat, 9 Sep 2017 20:32:41 +0200
Lukas Wunner <lukas@xxxxxxxxx> wrote:
> 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>
Looks good to me.
Note if anyone wants to add anything it'll only be exposed in the testing
branch of iio.git for a week or so - hence not in a state where I'm
unwilling to rebased. All tested-by's etc particularly welcome!
Applied to the togreg branch of iio.git and pushed out as testing for
the autobuilders to play with it.
Thanks,
Jonathan
> ---
> 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))
--
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