Hello,
This RFC is following first patch-set sent for DFSDM driver (https://www.spinics.net/lists/arm-kernel/msg557133.html). AS MFD driver has been rejected, a new way to integrate DFSDM has to be defined.
Aim of this RFC is to provide a base to discuss this redesign.
1) DFSDM hardware overview: ----------------------- The Digital Filter for Sigma Delta is a module dedicated to interface external sigma delta modulators to STM32 micro-controllers. It is targeted for: - Audio mode signal with Pulse density modulation (PDM) microphone - motor and Sensing mode with sigma delta ADC modulator
Main Features: - Up to 8 multiplexed input digital serial channel (SIT) . SPI (PDM compatible) or Manchester interface . Slave or master ( one main SPI CLK OUT for all interface) - Alternative inputs for 8 internal digital parallel channels (PIT) . 16 bits resolution . internal sources: ADC or memory - Digital signal processing: . 4 instances . Sincx filter (x : order 1 to 5) oversampling ratio up to 1024 . integrator: oversampling ratio up to 256 - Channel multiplexer . allow to connect SIT or PIT to filter . channel n can be connected SIT n or SIT n+1 - up to 24-bit output resolution . signed . sampling rate and resolution depend on filter parameters. - data offset correction - detector: . analog watchdog . short circuit detection . clock absence detection . extremes
For details on DFSDM IP, please refer to STM32F413 data-sheet chapter 15: http://www.st.com/content/ccc/resource/technical/document/reference_manual/g...
2) SW design proposal: --------------------- Patch-set associated to this RFC proposes an implementation of the DFSDM features shared between ASoC and IIO frameworks.
Patch-set is only a Skeleton of the drivers, so a base to discuss and validate a design. It contains minimum code to allow probing (with DT) and to expose the ASoC and IIO ABI. Hope that is sufficent in a first step to allow to focus on APIs.
In this patch-set there are two new APIs used: - IIO in-kern API: based on hw_customer API proposed by Lars - ASOC <-> IIO API inspired by API defined for hdmi-codec for ASoC/DRM interconnect. API is dedicated to DFSDM only.
Notice also that this design is based on following assumption: - Audio stream ABI interface is ASoC, no access to data through IIO ABI for PDM. - ASoC DMA should be used for audio transfer as designed for real time stream. - Need some runtime parameters exchange between ASoC and IIO due to the correlation between the sample frequency, the DFSDM decimation factor and the associated scaling.
- "ASoC: dmaengine_pcm: add copy support" patch: I added a patch in ASoC that allows to implement a copy function to process data after DMA transfer. Requested, as DFSDM samples captured contain channel ID on 8-LSB bits and need also a potential rescale to present DAT on 24-bits.
- "IIO: ADC: add sigma delta modulator support" patch: Simple dummy driver created to support external Sigma delta modulator. It is binded to DFSDM driver through hw_customer API.
Regards Arnaud
Arnaud Pouliquen (6): iio: Add hardware consumer support IIO: Add bindings for simple sigma delta adc IIO: ADC: add sigma delta modulator support ASoC: stm32: add DFSDM DAI support IIO: add bindings for stm32 DFSDM filter IIO: ADC: add stm32 DFSDM support
olivier moysan (1): ASoC: dmaengine_pcm: add copy support
.../devicetree/bindings/iio/adc/simple_sd_adc.txt | 13 + .../bindings/iio/adc/st,stm32-dfsdm-adc.txt | 125 ++++++ drivers/iio/Kconfig | 6 + drivers/iio/Makefile | 1 + drivers/iio/adc/Kconfig | 24 + drivers/iio/adc/Makefile | 2 + drivers/iio/adc/simple_sd_adc.c | 112 +++++ drivers/iio/adc/stm32-dfsdm-adc.c | 483 +++++++++++++++++++++ drivers/iio/adc/stm32-dfsdm-core.c | 273 ++++++++++++ drivers/iio/adc/stm32-dfsdm.h | 141 ++++++ drivers/iio/hw_consumer.c | 156 +++++++ include/linux/iio/hw_consumer.h | 12 + include/sound/dmaengine_pcm.h | 3 + include/sound/stm32-adfsdm.h | 80 ++++ sound/soc/Kconfig | 1 + sound/soc/Makefile | 1 + sound/soc/soc-generic-dmaengine-pcm.c | 37 +- sound/soc/stm/Kconfig | 10 + sound/soc/stm/Makefile | 2 + sound/soc/stm/stm32_adfsdm.c | 365 ++++++++++++++++ 20 files changed, 1845 insertions(+), 2 deletions(-) create mode 100644 Documentation/devicetree/bindings/iio/adc/simple_sd_adc.txt create mode 100644 Documentation/devicetree/bindings/iio/adc/st,stm32-dfsdm-adc.txt create mode 100644 drivers/iio/adc/simple_sd_adc.c create mode 100644 drivers/iio/adc/stm32-dfsdm-adc.c create mode 100644 drivers/iio/adc/stm32-dfsdm-core.c create mode 100644 drivers/iio/adc/stm32-dfsdm.h create mode 100644 drivers/iio/hw_consumer.c create mode 100644 include/linux/iio/hw_consumer.h create mode 100644 include/sound/stm32-adfsdm.h create mode 100644 sound/soc/stm/Kconfig create mode 100644 sound/soc/stm/Makefile create mode 100644 sound/soc/stm/stm32_adfsdm.c