Re: [PATCH 4/4] iio: dac: stm32: add support for waveform generator

From: Fabrice Gasnier
Date: Wed Apr 05 2017 - 12:47:17 EST

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JonathanOn 04/02/2017 02:19 PM, Jonathan Cameron wrote:
> On 31/03/17 12:45, Fabrice Gasnier wrote:
>> STM32 DAC has built-in noise or triangle waveform generator.
>> Waveform generator requires trigger to be configured.
>> - "wave" extended attribute selects noise or triangle.
>> - "mamp" extended attribute selects either LFSR (linear feedback
>> shift register) mask for noise waveform, OR triangle amplitude.
>>
>> Signed-off-by: Fabrice Gasnier <fabrice.gasnier@xxxxxx>
>
> Looks like AN3126 is the relevant doc.
> (a quick note from this relevant to earlier patches- doc says
> 1-3 channels - perhaps build that from the start with that
> possibility in mind).
Hi Jonathan,

Just to clarify this, some products like STM32F334xx have 3 channels,
yes. Several STM32 DAC IPs (& so registers) are instantiated: DAC1 have
two outputs (dac1_out1 & dac1_out2), DAC2 have one output (e.g.
dac2_out1). Driver can be instantiated several times. Is it ok ?

>
> As you probably know, this wanders into a large chunk of 'poorly'
> defined ABI within IIO as it stands.
>
> Note there are a number of waveform generators still in staging.
> Not a lot of movement on getting them out of staging unfortunately
> (so far!)
>
> However, let us keep those drivers in mind as we work on ABI and
> I definitely want some input from someone at Analog.
> Lars, who is best for this? I see at least some of these were
> originally Michael's work.
>
> They do have partial docs under
> drivers/staging/iio/Documentation/sysfs-bus-iio-dds
> I'll highlight thoughts from there as I look through this...

Thanks for pointing this out.

>
>
>> ---
>> Documentation/ABI/testing/sysfs-bus-iio-dac-stm32 | 32 ++++++
>> drivers/iio/dac/stm32-dac.c | 124 ++++++++++++++++++++++
>> 2 files changed, 156 insertions(+)
>> 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..c2432e1
>> --- /dev/null
>> +++ b/Documentation/ABI/testing/sysfs-bus-iio-dac-stm32
>> @@ -0,0 +1,32 @@
>> +What: /sys/bus/iio/devices/iio:deviceX/wave
>> +What: /sys/bus/iio/devices/iio:deviceX/wave_available
> Needs to be channel associated. Whilst in your case you have basically
> a pair of single channel devices, in more general case, it's not usual
> to have multiple parallel waveform generators clocked together.
>
> Old ABI is:
> What: /sys/bus/iio/devices/.../out_altvoltageX_outY_wavetype etc
>
I'll rework this in V2.
>
>> +KernelVersion: 4.12
>> +Contact: fabrice.gasnier@xxxxxx
>> +Description:
>> + List and/or select waveform generation provided by STM32 DAC:
>> + - "none": (default) means normal DAC operations
> none kind of hints at nothing coming out. Perhaps 'flat' would be closer?
> i.e. only changes when someone tells it to.
>
>> + - "noise": select noise waveform
>> + - "triangle": select triangle waveform
>> + Note: when waveform generator is used, writing _raw sysfs entry
>> + adds a DC offset to generated waveform. Reading it reports
>> + current output value.
> Interesting. This gets fiddly but one option would be to describe the whole
> device as a dds.
>
> Then we have flat type above, combined with an _offset.

I'll update from 'none' to 'flat' in V2, and use _offset.
>
>> +
>> +What: /sys/bus/iio/devices/iio:deviceX/mamp
>> +What: /sys/bus/iio/devices/iio:deviceX/mamp_available
>> +KernelVersion: 4.12
>> +Contact: fabrice.gasnier@xxxxxx
>> +Description:
>> + List and select mask/amplitude used for noise/triangle waveform
>> + generator, which are:
>> + - "0": unmask bit 0 of LFSR / triangle amplitude equal to 1
>> + - "1": unmask bit [1:0] of LFSR / triangle amplitude equal to 3
>> + - "2": unmask bit [2:0] of LFSR / triangle amplitude equal to 7
>> + - "3": unmask bit [3:0] of LFSR / triangle amplitude equal to 15
>> + - "4": unmask bit [4:0] of LFSR / triangle amplitude equal to 31
>> + - "5": unmask bit [5:0] of LFSR / triangle amplitude equal to 63
>> + - "6": unmask bit [6:0] of LFSR / triangle amplitude equal to 127
>> + - "7": unmask bit [7:0] of LFSR / triangle amplitude equal to 255
>> + - "8": unmask bit [8:0] of LFSR / triangle amplitude equal to 511
>> + - "9": unmask bit [9:0] of LFSR / triangle amplitude equal to 1023
>> + - "10": unmask bit [10:0] of LFSR / triangle amplitude equal to 2047
>> + - "11": unmask bit [11:0] of LFSR / triangle amplitude equal to 4095
> I don't fully understand what is going on here - so I'm guessing somewhat.
Sorry for this, this is basically amplitude.

I think best is to rename above to something like 'amplitude' and
'amplitude_available'.

I'll rework this in V2.
>
>
> Let us try describing these generically. If we define standard 'forms' of each
> waveform type. Say a 0 to 1 V peak to peak, then we could use _scale to control
> this nicely.
>
>> diff --git a/drivers/iio/dac/stm32-dac.c b/drivers/iio/dac/stm32-dac.c
>> index 62e43e9..d7dda78 100644
>> --- a/drivers/iio/dac/stm32-dac.c
>> +++ b/drivers/iio/dac/stm32-dac.c
>> @@ -41,10 +41,14 @@
>> /**
>> * struct stm32_dac - private data of DAC driver
>> * @common: reference to DAC common data
>> + * @wave: waveform generator
>> + * @mamp: waveform mask/amplitude
>> * @swtrig: Using software trigger
>> */
>> struct stm32_dac {
>> struct stm32_dac_common *common;
>> + u32 wave;
>> + u32 mamp;
>> bool swtrig;
>> };
>>
>> @@ -157,6 +161,24 @@ static int stm32_dac_is_enabled(struct stm32_dac *dac, int channel)
>> return !!en;
>> }
>>
>> +static int stm32_dac_wavegen(struct stm32_dac *dac, int channel)
>> +{
>> + struct regmap *regmap = dac->common->regmap;
>> + u32 mask, val;
>> +
>> + if (channel == STM32_DAC_CHANNEL_1) {
>> + val = FIELD_PREP(STM32_DAC_CR_WAVE1, dac->wave) |
>> + FIELD_PREP(STM32_DAC_CR_MAMP1, dac->mamp);
>> + mask = STM32_DAC_CR_WAVE1 | STM32_DAC_CR_MAMP1;
>> + } else {
>> + val = FIELD_PREP(STM32_DAC_CR_WAVE2, dac->wave) |
>> + FIELD_PREP(STM32_DAC_CR_MAMP2, dac->mamp);
>> + mask = STM32_DAC_CR_WAVE2 | STM32_DAC_CR_MAMP2;
>> + }
>> +
>> + return regmap_update_bits(regmap, STM32_DAC_CR, mask, val);
>> +}
>> +
>> static int stm32_dac_enable(struct iio_dev *indio_dev, int channel)
>> {
>> struct stm32_dac *dac = iio_priv(indio_dev);
>> @@ -164,6 +186,17 @@ static int stm32_dac_enable(struct iio_dev *indio_dev, int channel)
>> STM32_DAC_CR_EN1 : STM32_DAC_CR_EN2;
>> int ret;
>>
>> + if (dac->wave && !indio_dev->trig) {
>> + dev_err(&indio_dev->dev, "Wavegen requires a trigger\n");
>> + return -EINVAL;
>> + }
>> +
>> + ret = stm32_dac_wavegen(dac, channel);
>> + if (ret < 0) {
>> + dev_err(&indio_dev->dev, "Wavegen setup failed\n");
>> + return ret;
>> + }
>> +
>> ret = stm32_dac_set_trig(dac, indio_dev->trig, channel);
>> if (ret < 0) {
>> dev_err(&indio_dev->dev, "Trigger setup failed\n");
>> @@ -291,6 +324,96 @@ static int stm32_dac_debugfs_reg_access(struct iio_dev *indio_dev,
>> .driver_module = THIS_MODULE,
>> };
>>
>> +/* waveform generator wave selection */
>> +static const char * const stm32_dac_wave_desc[] = {
>> + "none",
>> + "noise",
>> + "triangle",
>> +};
>> +
>> +static int stm32_dac_set_wave(struct iio_dev *indio_dev,
>> + const struct iio_chan_spec *chan,
>> + unsigned int type)
>> +{
>> + struct stm32_dac *dac = iio_priv(indio_dev);
>> +
>> + if (stm32_dac_is_enabled(dac, chan->channel))
>> + return -EBUSY;
>> + dac->wave = type;
>> +
>> + return 0;
>> +}
>> +
>> +static int stm32_dac_get_wave(struct iio_dev *indio_dev,
>> + const struct iio_chan_spec *chan)
>> +{
>> + struct stm32_dac *dac = iio_priv(indio_dev);
>> +
>> + return dac->wave;
>> +}
>> +
>> +static const struct iio_enum stm32_dac_wave_enum = {
>> + .items = stm32_dac_wave_desc,
>> + .num_items = ARRAY_SIZE(stm32_dac_wave_desc),
>> + .get = stm32_dac_get_wave,
>> + .set = stm32_dac_set_wave,
>> +};
>> +
>> +/*
>> + * waveform generator mask/amplitude selection:
>> + * - noise: LFSR mask (linear feedback shift register, umasks bit 0, [1:0]...)
>> + * - triangle: amplitude (equal to 1, 3, 5, 7... 4095)
>> + */
>> +static const char * const stm32_dac_mamp_desc[] = {
>> + "0", "1", "2", "3", "4", "5", "6", "7", "8", "9", "10", "11",
>> +};
>> +
>> +static int stm32_dac_set_mamp(struct iio_dev *indio_dev,
>> + const struct iio_chan_spec *chan,
>> + unsigned int type)
>> +{
>> + struct stm32_dac *dac = iio_priv(indio_dev);
>> +
>> + if (stm32_dac_is_enabled(dac, chan->channel))
>> + return -EBUSY;
>> + dac->mamp = type;
>> +
>> + return 0;
>> +}
>> +
>> +static int stm32_dac_get_mamp(struct iio_dev *indio_dev,
>> + const struct iio_chan_spec *chan)
>> +{
>> + struct stm32_dac *dac = iio_priv(indio_dev);
>> +
>> + return dac->mamp;
>> +}
>> +
>> +static const struct iio_enum stm32_dac_mamp_enum = {
>> + .items = stm32_dac_mamp_desc,
>> + .num_items = ARRAY_SIZE(stm32_dac_mamp_desc),
>> + .get = stm32_dac_get_mamp,
>> + .set = stm32_dac_set_mamp,
>> +};
>> +
>> +static const struct iio_chan_spec_ext_info stm32_dac_ext_info[] = {
>> + IIO_ENUM("wave", IIO_SHARED_BY_ALL, &stm32_dac_wave_enum),
>> + {
>> + .name = "wave_available",
>> + .shared = IIO_SHARED_BY_ALL,
>> + .read = iio_enum_available_read,
>> + .private = (uintptr_t)&stm32_dac_wave_enum,
>> + },
>> + IIO_ENUM("mamp", IIO_SHARED_BY_ALL, &stm32_dac_mamp_enum),
>> + {
>> + .name = "mamp_available",
>> + .shared = IIO_SHARED_BY_ALL,
>> + .read = iio_enum_available_read,
>> + .private = (uintptr_t)&stm32_dac_mamp_enum,
>> + },
>> + {},
>> +};
>> +
>> #define STM32_DAC_CHANNEL(chan, name) { \
>> .type = IIO_VOLTAGE, \
>> .indexed = 1, \
>> @@ -306,6 +429,7 @@ static int stm32_dac_debugfs_reg_access(struct iio_dev *indio_dev,
>> .storagebits = 16, \
>> }, \
>> .datasheet_name = name, \
>> + .ext_info = stm32_dac_ext_info \
>> }
>>
>> static const struct iio_chan_spec stm32_dac_channels[] = {
>>
>

Next message: Priit Laes: "[PATCH] clk: sunxi-ng: Display index when clock registration fails"
Previous message: Oleg Nesterov: "Re: [RFC][PATCH 2/2] exec: If possible don't wait for ptraced threads to be reaped"
In reply to: Jonathan Cameron: "Re: [PATCH 4/4] iio: dac: stm32: add support for waveform generator"
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