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 <[email protected]>
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). 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... > --- > 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 > +KernelVersion: 4.12 > +Contact: [email protected] > +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. > + > +What: /sys/bus/iio/devices/iio:deviceX/mamp > +What: /sys/bus/iio/devices/iio:deviceX/mamp_available > +KernelVersion: 4.12 > +Contact: [email protected] > +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. 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[] = { >
