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SubjectRe: [PATCH v2 5/5] iio: dac: stm32: add support for waveform generator
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On 04/09/2017 11:34 AM, Jonathan Cameron wrote:
> On 06/04/17 17:11, Fabrice Gasnier wrote:
>> STM32 DAC has built-in noise or triangle waveform generator.
>> - "wavetype" extended attribute selects noise or triangle.
>> - "amplitude" extended attribute selects amplitude for waveform generator
>>
>> A DC offset can be added to waveform generator output. This can be done
>> using out_voltage[1/2]_offset
>>
>> Waveform generator requires a trigger to be configured, to increment /
>> decrement internal counter in case of triangle generator. Noise
>> generator is a bit different, but also requires a trigger to generate
>> samples.
>>
>> Signed-off-by: Fabrice Gasnier <fabrice.gasnier@st.com>
>
> Various bits inline. Mostly I think the blockers on this will be
> making sure the ABI defined is generic enough to handle the more crazy
> DDS chips out there... (basically the ones doing frequency modulation).
>
> Jonathan
>> ---
>> Changes in v2:
>> - use _offset parameter to add DC offset to waveform generator
> Conceptually this offset is just the normal DAC output value (particularly
yes
> in the flat case) I guess we can paper over this by having the _raw
> and this always have th same value, but it's a little inelegant.
> Still people are going to expect _raw to control it when in DAC mode but
> that makes limited sense in DDS mode.
>
> Mind you nothing stops us defining all DDS channels as the sum of whatever
> the DDS is doing and whatever is _raw is set to. Perhaps we tidy this up
> purely through documentation. Think of the DDS as a modulation on top
> of the DAC...
>
>> - Rework ABI to better fit existing DDS ABI: use out_voltageY_wavetype,
>> out_voltage_wavetype_available, out_voltageY_amplitude,
>> out_voltage_amplitude_available
> Hmm. I'm thinking those amplitude values aren't nice and don't fit well
> with the more general ABI.
>
> I suggested (but didn't really expand upon) having standard defined types
> for each waveform then using scale to control the amplitude.

Do you mean _scale attribute ?
>
> Is that something that might work here?

I probably miss the point here...
>
> So say we have our triangle standard form having an amplitude of 1V Peak to
> Peak. Then we can use scale to make it whatever we actually have in this
> case? The docs for wave type will need to describe those standard forms
> though.
... scale is fixed here, in line with _raw attribute. In 'amplitude'
description for STM32 DAC here (e.g. from 1...4095), same scale is used.
Can you elaborate ?

>
> Hmm. Whether this is worth doing is unclear however as we'll still have
> to describe the 'frequency' in terms of the clock ticks (here the triggers)

Describing frequency may be an issue, not sure it makes senses in this
case: 'clock ticks', e.g. triggers here may be timers, but also an EXTI
(external...), or even software trig perhaps.

> So maybe amplitude is worth having. Again, looking for input from ADI lot
> on this... There are some really fiddly cases to describe were we are doing
> symbol encoding so have multiple waveforms that we are switching between based
> on some external signal. Any ABI needs to encompass that sort of usage.
> Parts like the AD9833 for example...
>
>> - Better explain trigger usage in case of waveform generator.
>> ---
>> Documentation/ABI/testing/sysfs-bus-iio-dac-stm32 | 16 +++
>> drivers/iio/dac/stm32-dac-core.h | 4 +
>> drivers/iio/dac/stm32-dac.c | 158 +++++++++++++++++++++-
>> 3 files changed, 177 insertions(+), 1 deletion(-)
>> create mode 100644 Documentation/ABI/testing/sysfs-bus-iio-dac-stm32
>>
>> diff --git a/Documentation/ABI/testing/sysfs-bus-iio-dac-stm32 b/Documentation/ABI/testing/sysfs-bus-iio-dac-stm32
>> new file mode 100644
>> index 0000000..8f1fa009
>> --- /dev/null
>> +++ b/Documentation/ABI/testing/sysfs-bus-iio-dac-stm32
> Fair enough to initially introduced these for this part only, but I'd very
> much like to see us agree on these sufficiently to get them into the main
> docs asap so we have something to work with for getting the DDS chips out
> of staging...
>> @@ -0,0 +1,16 @@
>> +What: /sys/bus/iio/devices/iio:deviceX/out_voltageY_wavetype
>> +What: /sys/bus/iio/devices/iio:deviceX/out_voltage_wavetype_available
>> +KernelVersion: 4.12
>> +Contact: fabrice.gasnier@st.com
>> +Description:
>> + List and/or select waveform generation provided by STM32 DAC:
>> + - "flat": waveform generator disabled (default)
>> + - "noise": select noise waveform
>> + - "triangle": select triangle waveform
>> +
>> +What: /sys/bus/iio/devices/iio:deviceX/out_voltageY_amplitude
>> +What: /sys/bus/iio/devices/iio:deviceX/out_voltage_amplitude_available
>> +KernelVersion: 4.12
>> +Contact: fabrice.gasnier@st.com
>> +Description:
>> + List and/or select amplitude used for waveform generator
>> diff --git a/drivers/iio/dac/stm32-dac-core.h b/drivers/iio/dac/stm32-dac-core.h
>> index e51a468..0f02975 100644
>> --- a/drivers/iio/dac/stm32-dac-core.h
>> +++ b/drivers/iio/dac/stm32-dac-core.h
>> @@ -37,8 +37,12 @@
>> #define STM32H7_DAC_CR_TEN1 BIT(1)
>> #define STM32H7_DAC_CR_TSEL1_SHIFT 2
>> #define STM32H7_DAC_CR_TSEL1 GENMASK(5, 2)
>> +#define STM32_DAC_CR_WAVE1 GENMASK(7, 6)
>> +#define STM32_DAC_CR_MAMP1 GENMASK(11, 8)
>> #define STM32H7_DAC_CR_HFSEL BIT(15)
>> #define STM32_DAC_CR_EN2 BIT(16)
>> +#define STM32_DAC_CR_WAVE2 GENMASK(23, 22)
>> +#define STM32_DAC_CR_MAMP2 GENMASK(27, 24)
>>
>> /* STM32_DAC_SWTRIGR bit fields */
>> #define STM32_DAC_SWTRIGR_SWTRIG1 BIT(0)
>> diff --git a/drivers/iio/dac/stm32-dac.c b/drivers/iio/dac/stm32-dac.c
>> index a7a078e..2ed75db 100644
>> --- a/drivers/iio/dac/stm32-dac.c
>> +++ b/drivers/iio/dac/stm32-dac.c
>> @@ -42,10 +42,12 @@
>> /**
>> * struct stm32_dac - private data of DAC driver
>> * @common: reference to DAC common data
>> + * @wavetype: waveform generator
>> * @swtrig: Using software trigger
>> */
>> struct stm32_dac {
>> struct stm32_dac_common *common;
>> + u32 wavetype;
>> bool swtrig;
>> };
>>
>> @@ -222,6 +224,29 @@ static int stm32_dac_set_value(struct stm32_dac *dac, int channel, int val)
>> return ret;
>> }
>>
>> +static int stm32_dac_get_offset(struct stm32_dac *dac, int channel, int *val)
>> +{
>> + int ret;
>> +
>> + /* Offset is only relevant in waveform generation mode. */
>> + if (!dac->wavetype) {
>> + *val = 0;
>> + return IIO_VAL_INT;
>> + }
>> +
>> + /*
>> + * In waveform generation mode, DC offset in DHR is added to waveform
>> + * generator output, then stored to DOR (data output register).
>> + * Read offset from DHR.
>> + */
> Just thinking what fun we could have if we do the fifo based output to push
> this that I was suggesting for the previous patch ;) triangles on top
> of fun general waveforms..
>
>> + if (STM32_DAC_IS_CHAN_1(channel))
>> + ret = regmap_read(dac->common->regmap, STM32_DAC_DHR12R1, val);
>> + else
>> + ret = regmap_read(dac->common->regmap, STM32_DAC_DHR12R2, val);
>> +
>> + return ret ? ret : IIO_VAL_INT;
>> +}
>> +
>> static int stm32_dac_read_raw(struct iio_dev *indio_dev,
>> struct iio_chan_spec const *chan,
>> int *val, int *val2, long mask)
>> @@ -231,6 +256,8 @@ static int stm32_dac_read_raw(struct iio_dev *indio_dev,
>> switch (mask) {
>> case IIO_CHAN_INFO_RAW:
>> return stm32_dac_get_value(dac, chan->channel, val);
>> + case IIO_CHAN_INFO_OFFSET:
>> + return stm32_dac_get_offset(dac, chan->channel, val);
>> case IIO_CHAN_INFO_SCALE:
>> *val = dac->common->vref_mv;
>> *val2 = chan->scan_type.realbits;
>> @@ -247,8 +274,16 @@ static int stm32_dac_write_raw(struct iio_dev *indio_dev,
>> struct stm32_dac *dac = iio_priv(indio_dev);
>>
>> switch (mask) {
>> + case IIO_CHAN_INFO_OFFSET:
>> + /* Offset only makes sense in waveform generation mode */
>> + if (dac->wavetype)
>> + return stm32_dac_set_value(dac, chan->channel, val);
>> + return -EBUSY;
> Yeah, I think I sent you down a blind alley here. If people agree, lets
> just define DDS signals as always being the sum of _raw + the dds element.
> Then it's easy.
Ok, I can revert back to use _raw if this is fine ;-)

>> case IIO_CHAN_INFO_RAW:
>> - return stm32_dac_set_value(dac, chan->channel, val);
>> + if (!dac->wavetype)
>> + return stm32_dac_set_value(dac, chan->channel, val);
>> + /* raw value is read only in waveform generation mode */
>> + return -EBUSY;
>> default:
>> return -EINVAL;
>> }
>> @@ -334,6 +369,122 @@ static ssize_t stm32_dac_write_powerdown(struct iio_dev *indio_dev,
>> .set = stm32_dac_set_powerdown_mode,
>> };
>>
>> +/* waveform generator wave selection */
>> +static const char * const stm32_dac_wavetype_desc[] = {
>> + "flat",
>> + "noise",
>> + "triangle",
>> +};
>> +
>> +static int stm32_dac_set_wavetype(struct iio_dev *indio_dev,
>> + const struct iio_chan_spec *chan,
>> + unsigned int wavetype)
>> +{
>> + struct stm32_dac *dac = iio_priv(indio_dev);
>> + u32 mask, val;
>> + int ret;
>> +
>> + /*
>> + * Waveform generator requires a trigger to be configured, to increment
>> + * or decrement internal counter in case of triangle generator. Noise
>> + * generator is a bit different, but also requires a trigger to
>> + * generate samples.
>> + */
>> + if (wavetype && !indio_dev->trig)
>> + dev_dbg(&indio_dev->dev, "Wavegen requires a trigger\n");
>> +
>> + if (STM32_DAC_IS_CHAN_1(chan->channel)) {
>> + val = FIELD_PREP(STM32_DAC_CR_WAVE1, wavetype);
>> + mask = STM32_DAC_CR_WAVE1;
>> + } else {
>> + val = FIELD_PREP(STM32_DAC_CR_WAVE2, wavetype);
>> + mask = STM32_DAC_CR_WAVE2;
>> + }
>> +
>> + ret = regmap_update_bits(dac->common->regmap, STM32_DAC_CR, mask, val);
>> + if (ret)
>> + return ret;
>> + dac->wavetype = wavetype;
>> +
>> + return 0;
>> +}
>> +
>> +static int stm32_dac_get_wavetype(struct iio_dev *indio_dev,
>> + const struct iio_chan_spec *chan)
>> +{
>> + struct stm32_dac *dac = iio_priv(indio_dev);
>> + u32 val;
>> + int ret;
>> +
>> + ret = regmap_read(dac->common->regmap, STM32_DAC_CR, &val);
>> + if (ret < 0)
>> + return ret;
>> +
>> + if (STM32_DAC_IS_CHAN_1(chan->channel))
>> + return FIELD_GET(STM32_DAC_CR_WAVE1, val);
>> + else
>> + return FIELD_GET(STM32_DAC_CR_WAVE2, val);
>> +}
>> +
>> +static const struct iio_enum stm32_dac_wavetype_enum = {
>> + .items = stm32_dac_wavetype_desc,
>> + .num_items = ARRAY_SIZE(stm32_dac_wavetype_desc),
>> + .get = stm32_dac_get_wavetype,
>> + .set = stm32_dac_set_wavetype,
>> +};
>> +
>> +/*
>> + * waveform generator mamp selection: mask/amplitude
>> + * - noise: LFSR mask (linear feedback shift register, umasks bit 0, [1:0]...)
> This needs breaking out into two attributes - for noise it isn't amplitude in
> any conventional sense... Keep the result device specific for now. I'm not
> even sure what type of pseudo random source that actually is...
Do you suggest to create specific attribute for this ? This will end-up
to write same register/bitfield as 'amplitude' for triangle generator.

Thanks & Regards,
Fabrice

> If anyone wants to figure it out it would be great to document it in a general
> form!
>
>> + * - triangle: amplitude (equal to 1, 3, 5, 7... 4095)
>> + */
>> +static const char * const stm32_dac_amplitude_desc[] = {
>> + "1", "3", "7", "15", "31", "63", "127", "255", "511", "1023", "2047",
>> + "4095",
>> +};
>> +
>> +static int stm32_dac_set_amplitude(struct iio_dev *indio_dev,
>> + const struct iio_chan_spec *chan,
>> + unsigned int amplitude)
>> +{
>> + struct stm32_dac *dac = iio_priv(indio_dev);
>> + u32 mask, val;
>> +
>> + if (STM32_DAC_IS_CHAN_1(chan->channel)) {
>> + val = FIELD_PREP(STM32_DAC_CR_MAMP1, amplitude);
>> + mask = STM32_DAC_CR_MAMP1;
>> + } else {
>> + val = FIELD_PREP(STM32_DAC_CR_MAMP2, amplitude);
>> + mask = STM32_DAC_CR_MAMP2;
>> + }
>> +
>> + return regmap_update_bits(dac->common->regmap, STM32_DAC_CR, mask, val);
>> +}
>> +
>> +static int stm32_dac_get_amplitude(struct iio_dev *indio_dev,
>> + const struct iio_chan_spec *chan)
>> +{
>> + struct stm32_dac *dac = iio_priv(indio_dev);
>> + u32 val;
>> + int ret;
>> +
>> + ret = regmap_read(dac->common->regmap, STM32_DAC_CR, &val);
>> + if (ret < 0)
>> + return ret;
>> +
>> + if (STM32_DAC_IS_CHAN_1(chan->channel))
>> + return FIELD_GET(STM32_DAC_CR_MAMP1, val);
>> + else
>> + return FIELD_GET(STM32_DAC_CR_MAMP2, val);
>> +}
>> +
>> +static const struct iio_enum stm32_dac_amplitude_enum = {
>> + .items = stm32_dac_amplitude_desc,
>> + .num_items = ARRAY_SIZE(stm32_dac_amplitude_desc),
>> + .get = stm32_dac_get_amplitude,
>> + .set = stm32_dac_set_amplitude,
>> +};
>> +
>> static const struct iio_chan_spec_ext_info stm32_dac_ext_info[] = {
>> {
>> .name = "powerdown",
>> @@ -343,6 +494,10 @@ static ssize_t stm32_dac_write_powerdown(struct iio_dev *indio_dev,
>> },
>> IIO_ENUM("powerdown_mode", IIO_SEPARATE, &stm32_dac_powerdown_mode_en),
>> IIO_ENUM_AVAILABLE("powerdown_mode", &stm32_dac_powerdown_mode_en),
>> + IIO_ENUM("wavetype", IIO_SEPARATE, &stm32_dac_wavetype_enum),
>> + IIO_ENUM_AVAILABLE("wavetype", &stm32_dac_wavetype_enum),
>> + IIO_ENUM("amplitude", IIO_SEPARATE, &stm32_dac_amplitude_enum),
>> + IIO_ENUM_AVAILABLE("amplitude", &stm32_dac_amplitude_enum),
>> {},
>> };
>>
>> @@ -352,6 +507,7 @@ static ssize_t stm32_dac_write_powerdown(struct iio_dev *indio_dev,
>> .output = 1, \
>> .channel = chan, \
>> .info_mask_separate = \
>> + BIT(IIO_CHAN_INFO_OFFSET) | \
>> BIT(IIO_CHAN_INFO_RAW) | \
>> BIT(IIO_CHAN_INFO_SCALE), \
>> /* scan_index is always 0 as num_channels is 1 */ \
>>
>

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