Re: [PATCH 2/7] MFD: add STM32 DFSDM support

From: Lee Jones <lee.jones@linaro.org>
To: Arnaud Pouliquen <arnaud.pouliquen@st.com>
Cc: Mark Rutland <mark.rutland@arm.com>,
	"devicetree@vger.kernel.org" <devicetree@vger.kernel.org>,
	"alsa-devel@alsa-project.org" <alsa-devel@alsa-project.org>,
	Lars-Peter Clausen <lars@metafoo.de>,
	Maxime Coquelin <mcoquelin.stm32@gmail.com>,
	Liam Girdwood <lgirdwood@gmail.com>,
	"linux-iio@vger.kernel.org" <linux-iio@vger.kernel.org>,
	Mark Brown <broonie@kernel.org>, Takashi Iwai <tiwai@suse.com>,
	Jaroslav Kysela <perex@perex.cz>,
	Rob Herring <robh+dt@kernel.org>,
	Jonathan Cameron <jic23@kernel.org>,
	Peter Meerwald-Stadler <pmeerw@pmeerw.net>,
	Hartmut Knaack <knaack.h@gmx.de>,
	"linux-arm-kernel@lists.infradead.org"
	<linux-arm-kernel@lists.infradead.org>,
	Alexandre TORGUE <alexandre.torgue@st.com>
Subject: Re: [PATCH 2/7] MFD: add STM32 DFSDM support
Date: Fri, 27 Jan 2017 10:15:45 +0000	[thread overview]
Message-ID: <20170127101545.g53uah57vgfu55o5@dell> (raw)
In-Reply-To: <a1aaaa20-ac00-b182-f1c1-63152be41135@st.com>

On Tue, 24 Jan 2017, Arnaud Pouliquen wrote:

> 
> 
> On 01/24/2017 12:36 PM, Lee Jones wrote:
> > On Tue, 24 Jan 2017, Arnaud Pouliquen wrote:
> >> On 01/24/2017 09:22 AM, Lee Jones wrote:
> >>> On Mon, 23 Jan 2017, Arnaud Pouliquen wrote:
> >>>
> >>>> DFSDM hardware IP can be used at the same time for ADC sigma delta
> >>>
> >>> Same time as what?
> >> DFSDM is used for ADC acquisition (through IIO) but also PDM microphone
> >> capture (through ASOC).
> >>>
> >>>> conversion and audio PDM microphone.
> >>>> MFD driver is in charge of configuring IP registers and managing IP clocks.
> >>>> For this it exports an API to handles filters and channels resources.
> >>>
> >>> This looks like an ADC driver?  What is it that makes it an MFD?
> >> Yes it a kind of ADC but that supports 2 features audio and iio.
> >> So it has to support 2 features based on 2 separate Frameworks.
> > 
> > I'm still unsure why it needs to live in MFD.
> > 
> > By the looks of it, this driver needs to move into IIO and you need to
> > call into it from ASoC.
> > 
> 
> I think i introduce confusion by speaking about ADC for audio...
> 
> 1) IIO handles sigma delta ADCs that can be used as example for motor
> controls. the aim is to get value based on an application request or
> using some triggers.
> example: http://www.ti.com/lit/ds/symlink/ads1202.pdf
> 
> 2) For audio part, we speak about Digital mems microphones that generate
> PDM format stream. PDM is a continuous real time stream dedicated to
> audio record and must be handled in ASOC ( codec Dmic part driver is
> /sound/soc/codec/dmic.c).
> DMIC example:
> http://www.st.com/content/ccc/resource/technical/document/datasheet/47/bd/d2/13/8d/fd/48/26/DM00121815.pdf/files/DM00121815.pdf/jcr:content/translations/en.DM00121815.pdf
> 
> Form my point of view it very strange to handle DMICs in IIO, as it is
> not designed to support audio streams.it is two separate features that
> are not compatible.
> 
> Now, from software point of view
> That would means that IIO declares ADCs that it can not expose, because
> DMIC is not IIO standard. But IIO inkern API needs that device is
> declared

> So i should define a specific API in IIO for ASOC driver.

Yes, this is what I think you should do.

MFD is not a dumping ground for devices that do not fit anywhere else.

> >>>> Signed-off-by: Arnaud Pouliquen <arnaud.pouliquen@st.com>
> >>>> ---
> >>>>  drivers/mfd/Kconfig             |   11 +
> >>>>  drivers/mfd/Makefile            |    2 +
> >>>>  drivers/mfd/stm32-dfsdm-reg.h   |  220 +++++++++
> >>>>  drivers/mfd/stm32-dfsdm.c       | 1044 +++++++++++++++++++++++++++++++++++++++
> >>>>  include/linux/mfd/stm32-dfsdm.h |  324 ++++++++++++
> >>>>  5 files changed, 1601 insertions(+)
> >>>>  create mode 100644 drivers/mfd/stm32-dfsdm-reg.h
> >>>>  create mode 100644 drivers/mfd/stm32-dfsdm.c
> >>>>  create mode 100644 include/linux/mfd/stm32-dfsdm.h
> >>>>
> >>>> diff --git a/drivers/mfd/Kconfig b/drivers/mfd/Kconfig
> >>>> index c6df644..4bb660b 100644
> >>>> --- a/drivers/mfd/Kconfig
> >>>> +++ b/drivers/mfd/Kconfig
> >>>> @@ -1607,6 +1607,17 @@ config MFD_STW481X
> >>>>  	  in various ST Microelectronics and ST-Ericsson embedded
> >>>>  	  Nomadik series.
> >>>>  
> >>>> +config MFD_STM32_DFSDM
> >>>> +	tristate "ST Microelectronics STM32 DFSDM"
> >>>> +	depends on (ARCH_STM32 && OF) || COMPILE_TEST
> >>>> +	select MFD_CORE
> >>>> +	select REGMAP
> >>>> +	select REGMAP_MMIO
> >>>> +	help
> >>>> +	  Select this option to enable the STM32 Digital Filter
> >>>> +	  for Sigma Delta Modulators (DFSDM) driver used
> >>>> +	  in various STM32 series.
> >>>> +
> >>>>  menu "Multimedia Capabilities Port drivers"
> >>>>  	depends on ARCH_SA1100
> >>>
> >>> [...]
> >>>
> >>
> >> Regards
> >> Arnaud
> > 

-- 
Lee Jones
Linaro STMicroelectronics Landing Team Lead
Linaro.org │ Open source software for ARM SoCs
Follow Linaro: Facebook | Twitter | Blog

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