forked from Minki/linux
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>
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@ -76,10 +76,6 @@ static int mcp320x_channel_to_tx_data(int device_index,
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int start_bit = 1;
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switch (device_index) {
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case mcp3001:
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case mcp3201:
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case mcp3301:
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return 0;
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case mcp3002:
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case mcp3202:
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return ((start_bit << 4) | (!differential << 3) |
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@ -100,20 +96,14 @@ static int mcp320x_adc_conversion(struct mcp320x *adc, u8 channel,
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{
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int ret;
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adc->rx_buf[0] = 0;
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adc->rx_buf[1] = 0;
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adc->tx_buf = mcp320x_channel_to_tx_data(device_index,
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channel, differential);
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memset(&adc->rx_buf, 0, sizeof(adc->rx_buf));
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if (adc->chip_info->num_channels > 1)
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adc->tx_buf = mcp320x_channel_to_tx_data(device_index, channel,
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differential);
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if (device_index != mcp3001 && device_index != mcp3201 && device_index != mcp3301) {
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ret = spi_sync(adc->spi, &adc->msg);
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if (ret < 0)
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return ret;
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} else {
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ret = spi_read(adc->spi, &adc->rx_buf, sizeof(adc->rx_buf));
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if (ret < 0)
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return ret;
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}
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ret = spi_sync(adc->spi, &adc->msg);
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if (ret < 0)
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return ret;
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switch (device_index) {
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case mcp3001:
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@ -322,9 +312,13 @@ static int mcp320x_probe(struct spi_device *spi)
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adc->transfer[0].len = sizeof(adc->tx_buf);
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adc->transfer[1].rx_buf = adc->rx_buf;
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adc->transfer[1].len = sizeof(adc->rx_buf);
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spi_message_init_with_transfers(&adc->msg, adc->transfer,
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ARRAY_SIZE(adc->transfer));
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if (chip_info->num_channels == 1)
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/* single-channel converters are rx only (no MOSI pin) */
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spi_message_init_with_transfers(&adc->msg,
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&adc->transfer[1], 1);
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else
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spi_message_init_with_transfers(&adc->msg, adc->transfer,
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ARRAY_SIZE(adc->transfer));
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adc->reg = devm_regulator_get(&spi->dev, "vref");
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if (IS_ERR(adc->reg))
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