linux-kernel - Re: [PATCH 0/5] Add support for STM32F4 SPI

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Message-ID: <b7424f2c-a644-fd60-7871-6306d035e688@st.com>
Date:   Mon, 17 Dec 2018 12:51:30 +0000
From:   Amelie DELAUNAY <amelie.delaunay@...com>
To:     Cezary Gapiński <cezary.gapinski@...il.com>,
        "Mark Brown" <broonie@...nel.org>,
        "linux-spi@...r.kernel.org" <linux-spi@...r.kernel.org>,
        "linux-stm32@...md-mailman.stormreply.com" 
        <linux-stm32@...md-mailman.stormreply.com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Rob Herring <robh+dt@...nel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>
CC:     Maxime Coquelin <mcoquelin.stm32@...il.com>,
        Alexandre TORGUE <alexandre.torgue@...com>,
        Mark Rutland <mark.rutland@....com>
Subject: Re: [PATCH 0/5] Add support for STM32F4 SPI

Hi Cezary,

On 12/10/18 8:05 PM, Cezary Gapiński wrote:
> Hi Amelie,
> 
> On Mon, 2018-12-10 at 12:37 +0000, Amelie DELAUNAY wrote:
>> Hi Cezary,
>>
>> On 12/9/18 2:53 PM, cezary.gapinski@...il.com wrote:
>>>
>>> From: Cezary Gapinski <cezary.gapinski@...il.com>
>>>
>>> This series of patches adds support for first generation of SPI
>>> interface
>>> for STM32F4 family.
>>>
>> First of all, thanks for adding STM32F4 SPI support.
> 
> Thanks for your answer and hints for correct approach to this driver.
> 
>>>
>>> This version of driver is mostly different to STM32H7 one. Based on
>>> linux
>>> kernel I2C drivers for STM32 where drivers were splited into
>>> STM32F4 and
>>> STM32F7 family the same approach seems to be sufficient for SPI
>>> STM32
>>> drivers. Therefore STM32H7 driver was moved to spi-stm32h7.c file
>>> and
>>> register and functions were renamed to be more specific to STM32H7.
>>>
>> You're right, STM32F4 SPI is slightly different from STM32H7 one:
>> register map/bits offsets are different and STM32H7 has an RX and TX
>> FIFO.
>> But if you have a look on STM32F7 SPI [1], you'll see that STM32F7
>> SPI
>> is based on STM32F4 SPI with new features (data frames & FIFOs) also
>> available on STM32H7 SPI.
>>
>> That's why STM32H7 SPI driver was called spi-stm32. The goal was to
>> use
>> compatible & match data to differentiate each STM32Fx specificities.
>>
>> You can have a look on how it is managed in drivers/rtc/rtc-stm32.c
>> (the
>> same driver covers 2 HW version of STM32 RTC), or in
>> drivers/iio/dac/stm32-dac-core.c and stm32-dac.c (the same driver
>> also
>> covers 2 HW version of STM32 DAC).
>> As your spi-stm32f4.c file is highly based on the existing spi-
>> stm32.c
>> file, I think that common code could be factored and specificities
>> could
>> be handled with compatible and match data.
> 
> I have seen these drivers before. I have been trying to do this for my
> previous approach and it is still on my second branch. There was not
> too much common parts and I have stuck with complex compatible data
> configurations. I thought that was too verbose, therefore I resigned
> for it and have gone into idea with two totally different files. I
> think I need to get down again to idea you proposed.
> 
> It seems to be more difficult approach and it is gonna take a while
> before I send second version of these patches.
> 
> Regards,
> Cezary
> 

Sure it isn't the easiest approach but it will be less difficult to add 
STM32F7 SPI support then!

I could test your second version when it will be available, on 
STM32H743i-eval if you don't have one.

Regards,
Amelie

>> Regards,
>> Amelie
>> [1]
>> https://www.st.com/content/ccc/resource/technical/document/reference_
>> manual/c5/cf/ef/52/c0/f1/4b/fa/DM00124865.pdf/files/DM00124865.pdf/jc
>> r:content/translations/en.DM00124865.pdf
>>
>>>
>>> For current version master mode with full-duplex and 8/16 bit data
>>> frame
>>> format are supported. There is no TX and RX FIFOs like in STM32H7.
>>> DMA capabilility is supported for messages longer than arbitrary
>>> number
>>> of bytes (that is set already to 16 bytes) when TX and RX channels
>>> are
>>> set at the same time.
>>>
>>> Cezary Gapinski (5):
>>>     spi: stm32: rename STM32 SPI registers and functions to STM32H7
>>>     spi: stm32: rename spi-stm32 to spi-stm32h7
>>>     spi: stm32: add driver for STM32F4 controller
>>>     ARM: dts: stm32: add SPI support on STM32F429 SoC
>>>     spi: stm32: add description about STM32F4 bindings
>>>
>>>    .../devicetree/bindings/spi/spi-stm32.txt          |    9 +-
>>>    arch/arm/boot/dts/stm32f429.dtsi                   |   60 +
>>>    drivers/spi/Kconfig                                |   18 +-
>>>    drivers/spi/Makefile                               |    3 +-
>>>    drivers/spi/spi-stm32.c                            | 1322 -----
>>> --------------
>>>    drivers/spi/spi-stm32f4.c                          | 1002
>>> +++++++++++++++
>>>    drivers/spi/spi-stm32h7.c                          | 1340
>>> ++++++++++++++++++++
>>>    7 files changed, 2424 insertions(+), 1330 deletions(-)
>>>    delete mode 100644 drivers/spi/spi-stm32.c
>>>    create mode 100644 drivers/spi/spi-stm32f4.c
>>>    create mode 100644 drivers/spi/spi-stm32h7.c