linux-kernel - Re: [PATCH 1/3] dt-bindings: spi: add SpacemiT K1 SPI support

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Message-ID: <3b815302-21f2-4ee2-bf83-c1dba77ce3d1@riscstar.com>
Date: Wed, 17 Sep 2025 18:40:31 -0500
From: Alex Elder <elder@...cstar.com>
To: Yixun Lan <dlan@...too.org>
Cc: broonie@...nel.org, robh@...nel.org, krzk+dt@...nel.org,
 conor+dt@...nel.org, linux-spi@...r.kernel.org, devicetree@...r.kernel.org,
 paul.walmsley@...ive.com, palmer@...belt.com, aou@...s.berkeley.edu,
 alex@...ti.fr, p.zabel@...gutronix.de, spacemit@...ts.linux.dev,
 linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/3] dt-bindings: spi: add SpacemiT K1 SPI support

On 9/17/25 6:15 PM, Yixun Lan wrote:
> Hi Alex,
> 
> On 17:07 Wed 17 Sep     , Alex Elder wrote:
>> Add support for the SPI controller implemented by the SpacemiT K1 SoC.
>>
>> Signed-off-by: Alex Elder <elder@...cstar.com>
>> ---
>>   .../bindings/spi/spacemit,k1-spi.yaml         | 94 +++++++++++++++++++
>>   1 file changed, 94 insertions(+)
>>   create mode 100644 Documentation/devicetree/bindings/spi/spacemit,k1-spi.yaml
>>
>> diff --git a/Documentation/devicetree/bindings/spi/spacemit,k1-spi.yaml b/Documentation/devicetree/bindings/spi/spacemit,k1-spi.yaml
>> new file mode 100644
>> index 0000000000000..5abd4fe268da9
>> --- /dev/null
>> +++ b/Documentation/devicetree/bindings/spi/spacemit,k1-spi.yaml
>> @@ -0,0 +1,94 @@
>> +# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
>> +%YAML 1.2
>> +---
>> +$id: http://devicetree.org/schemas/spi/spacemit,k1-spi.yaml#
>> +$schema: http://devicetree.org/meta-schemas/core.yaml#
>> +
>> +title: SpacemiT K1 SoC Serial Peripheral Interface (SPI)
>> +
>> +maintainers:
>> +  - Alex Elder <elder@...nel.org>
>> +
>> +description:
>> +  The SpacemiT K1 SoC implements a SPI controller that has two 32-entry
>> +  FIFOs, for transmit and receive.  Details are currently available in
>> +  section 18.2.1 of the K1 User Manual, found in the SpacemiT Keystone
>> +  K1 Documentation[1].  The controller transfers words using PIO.  DMA
>> +  transfers are supported as well, if both TX and RX DMA channels are
>> +  specified,
>> +
>> +  [1] https://developer.spacemit.com/documentation
>> +
>> +allOf:
>> +  - $ref: /schemas/spi/spi-controller.yaml#
>> +
>> +properties:
>> +  compatible:
>> +    enum:
>> +      - spacemit,k1-spi
> one enum is effectively equal to const..

OK.  That's an easy fix.

>> +
>> +  reg:
>> +    maxItems: 1
>> +
>> +  clocks:
>> +    items:
>> +      - description: Core clock
>> +      - description: Bus clock
>> +
>> +  clock-names:
>> +    items:
>> +      - const: core
>> +      - const: bus
>> +
>> +  resets:
>> +    maxItems: 1
>> +
>> +  interrupts:
>> +    maxItems: 1
>> +
>> +  dmas:
>> +    items:
>> +      - description: RX DMA channel
>> +      - description: TX DMA channel
>> +
>> +  dma-names:
>> +    items:
>> +      - const: rx
>> +      - const: tx
>> +
>> +  spacemit,k1-ssp-id:
>> +    description: SPI controller number
>> +    $ref: /schemas/types.yaml#/definitions/uint32
> could you explain a little bit why this vendor specific property should
> be introduced? I took a look at the code, and didn't get the reason
> behind.. or what's the problem of simply using "pdev->id"?

This property was carried over from the vendor code.  It is
optional, and if it isn't specified, the platform device ID (-1)
will be used.  It's just intended to provide a well-defined ID
for a particular SPI controller.

> we should really be careful to introduce vendor specific property..

If there were a standard way of doing this I'd love to use it.

And if it isn't necessary, please just explain to me why.  I
have no problem removing it.

>> +required:
>> +  - compatible
>> +  - reg
>> +  - clocks
>> +  - clock-names
>> +  - resets
>> +  - interrupts
>> +
>> +unevaluatedProperties: false
>> +
>> +examples:
>> +  - |
>> +
>> +    #include <dt-bindings/clock/spacemit,k1-syscon.h>
>> +    spi3: spi@...1c000 {
> label not needed for DT example

OK.

>> +        compatible = "spacemit,k1-spi";
>> +        reg = <0xd401c000 0x30>;
>> +        #address-cells = <1>;
>> +        #size-cells = <0>;
>> +        clocks = <&syscon_apbc CLK_SSP3>,
>> +                 <&syscon_apbc CLK_SSP3_BUS>;
>> +        clock-names = "core",
>> +                      "bus";
>> +        resets = <&syscon_apbc RESET_SSP3>;
>> +        interrupts-extended = <&plic 55>;
>> +        spacemit,k1-ssp-id = <3>;
>> +        dmas = <&pdma 20>,
>> +               <&pdma 19>;
>> +        dma-names = "rx",
>> +                    "tx";
> ..
>> +        status = "disabled";
> ditto, drop it

OK.  Thanks a lot for your quick review.  I'll wait a bit
(probably until Monday) before I send an update.

					-Alex

>> +    };
>> -- 
>> 2.48.1
>>
>