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

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Date:   Mon, 10 Dec 2018 12:37:56 +0000
From:   Amelie DELAUNAY <amelie.delaunay@...com>
To:     "cezary.gapinski@...il.com" <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 12/9/18 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.

> 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.

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/jcr: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
>