Re: [PATCH 1/2] dt-bindings: spi: Document the STM32 SPI bindings

[Amelie DELAUNAY]

On 06/21/2017 05:20 PM, Neil Armstrong wrote:
> On 06/21/2017 04:32 PM, Amelie Delaunay wrote:
> > This patch adds the documentation of device tree bindings
> > for the STM32 SPI controller.
> >
> > Signed-off-by: Amelie Delaunay <amelie.delaunay@xxxxxx>
> > ---
> >   .../devicetree/bindings/spi/spi-stm32.txt          | 60 ++++++++++++++++++++++
> >   1 file changed, 60 insertions(+)
> >   create mode 100644 Documentation/devicetree/bindings/spi/spi-stm32.txt
> >
> > diff --git a/Documentation/devicetree/bindings/spi/spi-stm32.txt b/Documentation/devicetree/bindings/spi/spi-stm32.txt
> > new file mode 100644
> > index 0000000..3958bf6
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/spi/spi-stm32.txt
> > @@ -0,0 +1,60 @@
> > +STMicroelectronics STM32 SPI Controller
> > +
> > +The STM32 SPI controller is used to communicate with external devices using
> > +the Serial Peripheral Interface. It supports full-duplex, half-duplex and
> > +simplex synchronous serial communication with external devices. It supports
> > +from 4 to 32-bit data size. Although it can be configured as master or slave,
> > +only master is supported by the driver.
> > +
> > +Required properties:
> > +- compatible: Must be "st,stm32-spi".
>
> Hi Amelie,
>
> What about the gen1 SPI devices like the F4 ?
>
> It should have been better to use SoC specific compatible, or specify the SPI HW gen like gen1 or gen2.
>
> Neil

Hi Neil,

The gen1 SPI controller embedded on F4/F7 is different from gen2 
embedded on H7 and just to illustrate this, there are 5 main registers 
(16-bit) on gen1 versus 10 main registers on gen2 (32-bit)! Their 
operating modes are different, fifo management and so on... Moreover, I 
know that the community is working on an SPI driver for F4.

I agree with you on the fact that it would be better to use a SoC 
specific compatible: I will send a v2 with "st,stm32h7-spi". This way, 
this will be aligned with what have been done for the I2S part of this 
controller: https://patchwork.kernel.org/patch/9737799/

By the way, I also noticed that my optional property "st,spi-midi-ns" 
doesn't fit with the example "st,spi-midi". I will fix that in the v2 
and keep "st,spi-midi-ns".

Regards,
Amelie

> > +- reg: Offset and length of the device's register set.
> > +- interrupts: Must contain the interrupt id.
> > +- clocks: Must contain an entry for spiclk (which feeds the internal clock
> > +	  generator).
> > +- #address-cells:  Number of cells required to define a chip select address.
> > +- #size-cells: Should be zero.
> > +
> > +Optional properties:
> > +- resets: Must contain the phandle to the reset controller.
> > +- A pinctrl state named "default" may be defined to set pins in mode of
> > +  operation for SPI transfer.
> > +- dmas: DMA specifiers for tx and rx dma. DMA fifo mode must be used. See the
> > +  STM32 DMA bindings, Documentation/devicetree/bindings/dma/stm32-dma.txt.
> > +- dma-names: DMA request names should include "tx" and "rx" if present.
> > +- cs-gpios: list of GPIO chip selects. See the SPI bus bindings,
> > +  Documentation/devicetree/bindings/spi/spi-bus.txt
> > +
> > +
> > +Child nodes represent devices on the SPI bus
> > +  See ../spi/spi-bus.txt
> > +
> > +Optional properties:
> > +- st,spi-midi-ns: (Master Inter-Data Idleness) minimum time delay in
> > +		  nanoseconds inserted between two consecutive data frames.
> > +
> > +
> > +Example:
> > +	spi2: spi@40003800 {
> > +		#address-cells = <1>;
> > +		#size-cells = <0>;
> > +		compatible = "st,stm32-spi";
> > +		reg = <0x40003800 0x400>;
> > +		interrupts = <36>;
> > +		clocks = <&rcc SPI2_CK>;
> > +		resets = <&rcc 1166>;
> > +		dmas = <&dmamux1 0 39 0x400 0x01>,
> > +		       <&dmamux1 1 40 0x400 0x01>;
> > +		dma-names = "rx", "tx";
> > +		pinctrl-0 = <&spi2_pins_b>;
> > +		pinctrl-names = "default";
> > +		status = "okay";
> > +		cs-gpios = <&gpioa 11 0>;
> > +
> > +		spidev@0 {
> > +			compatible = "spidev";
> > +			reg = <0>;
> > +			spi-max-frequency = <4000000>;
> > +			st,spi-midi = <4000>;
> > +		};
> > +	};