linux-kernel - Re: [PATCH 6/7] dt-bindings: spi: stm32: add stm32h7 st,spi-slave-underrun property

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Message-ID: <b03257a8-2236-c709-043d-ffa4e6b062a8@foss.st.com>
Date:   Thu, 4 May 2023 19:13:33 +0200
From:   Valentin CARON <valentin.caron@...s.st.com>
To:     Rob Herring <robh@...nel.org>
CC:     Mark Brown <broonie@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Alexandre Torgue <alexandre.torgue@...s.st.com>,
        Alain Volmat <alain.volmat@...s.st.com>,
        <linux-spi@...r.kernel.org>, <devicetree@...r.kernel.org>,
        <linux-stm32@...md-mailman.stormreply.com>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 6/7] dt-bindings: spi: stm32: add stm32h7
 st,spi-slave-underrun property


On 4/28/23 23:56, Rob Herring wrote:
> On Fri, Apr 28, 2023 at 02:15:23PM +0200, Valentin Caron wrote:
>> This property is used to enable and configure stm32h7 SPI controller to
>> handle underrun that could appear in slave mode.
>>
>> Signed-off-by: Valentin Caron <valentin.caron@...s.st.com>
>> ---
>>   .../devicetree/bindings/spi/st,stm32-spi.yaml     |  8 ++++++++
>>   MAINTAINERS                                       |  1 +
>>   include/dt-bindings/spi/spi-stm32.h               | 15 +++++++++++++++
>>   3 files changed, 24 insertions(+)
>>   create mode 100644 include/dt-bindings/spi/spi-stm32.h
>>
>> diff --git a/Documentation/devicetree/bindings/spi/st,stm32-spi.yaml b/Documentation/devicetree/bindings/spi/st,stm32-spi.yaml
>> index 1d26fa2658c5..e946ea71a247 100644
>> --- a/Documentation/devicetree/bindings/spi/st,stm32-spi.yaml
>> +++ b/Documentation/devicetree/bindings/spi/st,stm32-spi.yaml
>> @@ -28,6 +28,7 @@ allOf:
>>         properties:
>>           st,spi-midi-ns: false
>>           spi-slave: false
>> +        st,spi-slave-underrun: false
>>   
>>   properties:
>>     "#address-cells": true
>> @@ -70,6 +71,13 @@ properties:
>>         In case of spi-slave defined, if <0>, indicate that SS should be
>>         detected via the dedicated HW pin
>>   
>> +  st,spi-slave-underrun:
>> +    $ref: /schemas/types.yaml#/definitions/uint32-array
>> +    description:
>> +      First parameter enables and selects slave underrun reaction.
>> +      Refer to "dt-bindings/spi/spi-stm32.h" for the supported values.
>> +      Second parameter is the pattern in case of SPI_SEND_PATTERN mode.
> So, max 2 cells? Then:
>
> minItems: 1
> maxItems: 2
>
> Though I don't really think this belongs in DT. The driver implementing
> the SPI slave function defines all the rest of the protocol the slave
> implements. Why not this little bit? Perhaps there is no way for a SPI
> slave driver to tell the SPI controller which controller specific mode
> to use, so you abuse DT to configure the SPI controller. Also, with a
> controller specific response, then the slave driver is coupled to that
> SPI controller which isn't great either.
>
> Rob
I basically made this DT property to configure the controler and doesn't
give attention to the fact that this parameter can came from framework.

I will not rework this functionality, but simply let it down as we has
no demands on it.

Thanks for all your remarks,
Valentin