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Date: Sat, 24 Sep 2022 17:46:07 +0100
From: Jonathan Cameron <jic23@...nel.org>
To: Marcus Folkesson <marcus.folkesson@...il.com>
Cc: Kent Gustavsson <kent@...oris.se>,
Lars-Peter Clausen <lars@...afoo.de>,
Rob Herring <robh+dt@...nel.org>,
Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
Andy Shevchenko <andy.shevchenko@...il.com>,
linux-iio@...r.kernel.org, devicetree@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH v7] iio: adc: mcp3911: add support to set PGA
On Thu, 22 Sep 2022 21:46:39 +0200
Marcus Folkesson <marcus.folkesson@...il.com> wrote:
> Add support for setting the Programmable Gain Amplifiers by adjust the
> scale value.
>
> Signed-off-by: Marcus Folkesson <marcus.folkesson@...il.com>
> Reviewed-by: Andy Shevchenko <andy.shevchenko@...il.com>
Applied to the togreg branch of iio.git and pushed out as testing.
I considered slipping this into my 2nd IIO pull request for this cycle
at the last minute, but wasn't happy skipping normal time being beaten on
by 0-day and time in next, so I didn't. Hence this probably won't make
6.1, but Linus did hint he might do an rc8 in which case I may see
if GregKH will take a 3rd pull late next week.
If not, it'll be 6.2 material.
Thanks,
Jonathan
> ---
>
> Notes:
> Based on
> Link: https://lore.kernel.org/all/20220815061625.35568-1-marcus.folkesson@gmail.com/
>
> But with tmp0, tmp1 and tmp2 removed as those are not needed.
> Link: https://lore.kernel.org/all/202209220648.Wb6EtPat-lkp@intel.com/
>
> drivers/iio/adc/mcp3911.c | 104 +++++++++++++++++++++++++++++---------
> 1 file changed, 80 insertions(+), 24 deletions(-)
>
> diff --git a/drivers/iio/adc/mcp3911.c b/drivers/iio/adc/mcp3911.c
> index 0151258b456c..0d768006eabb 100644
> --- a/drivers/iio/adc/mcp3911.c
> +++ b/drivers/iio/adc/mcp3911.c
> @@ -29,6 +29,8 @@
> #define MCP3911_REG_MOD 0x06
> #define MCP3911_REG_PHASE 0x07
> #define MCP3911_REG_GAIN 0x09
> +#define MCP3911_GAIN_MASK(ch) (GENMASK(2, 0) << 3 * ch)
> +#define MCP3911_GAIN_VAL(ch, val) ((val << 3 * ch) & MCP3911_GAIN_MASK(ch))
>
> #define MCP3911_REG_STATUSCOM 0x0a
> #define MCP3911_STATUSCOM_DRHIZ BIT(12)
> @@ -59,8 +61,10 @@
> #define MCP3911_REG_WRITE(reg, id) ((((reg) << 1) | ((id) << 5) | (0 << 0)) & 0xff)
>
> #define MCP3911_NUM_CHANNELS 2
> +#define MCP3911_NUM_SCALES 6
>
> static const int mcp3911_osr_table[] = { 32, 64, 128, 256, 512, 1024, 2048, 4096 };
> +static u32 mcp3911_scale_table[MCP3911_NUM_SCALES][2];
>
> struct mcp3911 {
> struct spi_device *spi;
> @@ -69,6 +73,7 @@ struct mcp3911 {
> struct clk *clki;
> u32 dev_addr;
> struct iio_trigger *trig;
> + u32 gain[MCP3911_NUM_CHANNELS];
> struct {
> u32 channels[MCP3911_NUM_CHANNELS];
> s64 ts __aligned(8);
> @@ -145,6 +150,11 @@ static int mcp3911_read_avail(struct iio_dev *indio_dev,
> *vals = mcp3911_osr_table;
> *length = ARRAY_SIZE(mcp3911_osr_table);
> return IIO_AVAIL_LIST;
> + case IIO_CHAN_INFO_SCALE:
> + *type = IIO_VAL_INT_PLUS_NANO;
> + *vals = (int *)mcp3911_scale_table;
> + *length = ARRAY_SIZE(mcp3911_scale_table) * 2;
> + return IIO_AVAIL_LIST;
> default:
> return -EINVAL;
> }
> @@ -189,29 +199,9 @@ static int mcp3911_read_raw(struct iio_dev *indio_dev,
> break;
>
> case IIO_CHAN_INFO_SCALE:
> - if (adc->vref) {
> - ret = regulator_get_voltage(adc->vref);
> - if (ret < 0) {
> - dev_err(indio_dev->dev.parent,
> - "failed to get vref voltage: %d\n",
> - ret);
> - goto out;
> - }
> -
> - *val = ret / 1000;
> - } else {
> - *val = MCP3911_INT_VREF_MV;
> - }
> -
> - /*
> - * For 24bit Conversion
> - * Raw = ((Voltage)/(Vref) * 2^23 * Gain * 1.5
> - * Voltage = Raw * (Vref)/(2^23 * Gain * 1.5)
> - */
> -
> - /* val2 = (2^23 * 1.5) */
> - *val2 = 12582912;
> - ret = IIO_VAL_FRACTIONAL;
> + *val = mcp3911_scale_table[ilog2(adc->gain[channel->channel])][0];
> + *val2 = mcp3911_scale_table[ilog2(adc->gain[channel->channel])][1];
> + ret = IIO_VAL_INT_PLUS_NANO;
> break;
> }
>
> @@ -229,6 +219,18 @@ static int mcp3911_write_raw(struct iio_dev *indio_dev,
>
> mutex_lock(&adc->lock);
> switch (mask) {
> + case IIO_CHAN_INFO_SCALE:
> + for (int i = 0; i < MCP3911_NUM_SCALES; i++) {
> + if (val == mcp3911_scale_table[i][0] &&
> + val2 == mcp3911_scale_table[i][1]) {
> +
> + adc->gain[channel->channel] = BIT(i);
> + ret = mcp3911_update(adc, MCP3911_REG_GAIN,
> + MCP3911_GAIN_MASK(channel->channel),
> + MCP3911_GAIN_VAL(channel->channel, i), 1);
> + }
> + }
> + break;
> case IIO_CHAN_INFO_OFFSET:
> if (val2 != 0) {
> ret = -EINVAL;
> @@ -264,6 +266,44 @@ static int mcp3911_write_raw(struct iio_dev *indio_dev,
> return ret;
> }
>
> +static int mcp3911_calc_scale_table(struct mcp3911 *adc)
> +{
> + u32 ref = MCP3911_INT_VREF_MV;
> + u32 div;
> + int ret;
> + u64 tmp;
> +
> + if (adc->vref) {
> + ret = regulator_get_voltage(adc->vref);
> + if (ret < 0) {
> + dev_err(&adc->spi->dev,
> + "failed to get vref voltage: %d\n",
> + ret);
> + return ret;
> + }
> +
> + ref = ret / 1000;
> + }
> +
> + /*
> + * For 24-bit Conversion
> + * Raw = ((Voltage)/(Vref) * 2^23 * Gain * 1.5
> + * Voltage = Raw * (Vref)/(2^23 * Gain * 1.5)
> + *
> + * ref = Reference voltage
> + * div = (2^23 * 1.5 * gain) = 12582912 * gain
> + */
> + for (int i = 0; i < MCP3911_NUM_SCALES; i++) {
> + div = 12582912 * BIT(i);
> + tmp = div_s64((s64)ref * 1000000000LL, div);
> +
> + mcp3911_scale_table[i][0] = 0;
> + mcp3911_scale_table[i][1] = tmp;
> + }
> +
> + return 0;
> +}
> +
> #define MCP3911_CHAN(idx) { \
> .type = IIO_VOLTAGE, \
> .indexed = 1, \
> @@ -273,8 +313,10 @@ static int mcp3911_write_raw(struct iio_dev *indio_dev,
> .info_mask_separate = BIT(IIO_CHAN_INFO_RAW) | \
> BIT(IIO_CHAN_INFO_OFFSET) | \
> BIT(IIO_CHAN_INFO_SCALE), \
> - .info_mask_shared_by_type_available = \
> + .info_mask_shared_by_type_available = \
> BIT(IIO_CHAN_INFO_OVERSAMPLING_RATIO), \
> + .info_mask_separate_available = \
> + BIT(IIO_CHAN_INFO_SCALE), \
> .scan_type = { \
> .sign = 's', \
> .realbits = 24, \
> @@ -483,6 +525,20 @@ static int mcp3911_probe(struct spi_device *spi)
> if (ret)
> return ret;
>
> + ret = mcp3911_calc_scale_table(adc);
> + if (ret)
> + return ret;
> +
> + /* Set gain to 1 for all channels */
> + for (int i = 0; i < MCP3911_NUM_CHANNELS; i++) {
> + adc->gain[i] = 1;
> + ret = mcp3911_update(adc, MCP3911_REG_GAIN,
> + MCP3911_GAIN_MASK(i),
> + MCP3911_GAIN_VAL(i, 0), 1);
> + if (ret)
> + return ret;
> + }
> +
> indio_dev->name = spi_get_device_id(spi)->name;
> indio_dev->modes = INDIO_DIRECT_MODE;
> indio_dev->info = &mcp3911_info;
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