linux-kernel - Re: [PATCH 1/3] dt-bindings: spi: Add realtek,rtl9300-snand

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Message-ID: <0eea6407-9477-4fe6-a37a-c7996ccaf706@kernel.org>
Date: Mon, 14 Oct 2024 10:37:46 +0200
From: Krzysztof Kozlowski <krzk@...nel.org>
To: Chris Packham <chris.packham@...iedtelesis.co.nz>
Cc: broonie@...nel.org, robh@...nel.org, krzk+dt@...nel.org,
 conor+dt@...nel.org, tsbogend@...ha.franken.de, linux-spi@...r.kernel.org,
 devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-mips@...r.kernel.org
Subject: Re: [PATCH 1/3] dt-bindings: spi: Add realtek,rtl9300-snand

On 07/10/2024 22:49, Chris Packham wrote:
> 
> On 8/10/24 08:58, Chris Packham wrote:
>>
>> On 7/10/24 19:40, Krzysztof Kozlowski wrote:
>>> On Mon, Oct 07, 2024 at 12:33:45PM +1300, Chris Packham wrote:
>>>> Add a dtschema for the SPI-NAND controller on the RTL9300 SoCs. The
>>>> controller supports
>>>>   * Serial/Dual/Quad data with
>>>>   * PIO and DMA data read/write operation
>>>>   * Configurable flash access timing
>>>>
>>>> Signed-off-by: Chris Packham <chris.packham@...iedtelesis.co.nz>
>>>> ---
>>>>   .../bindings/spi/realtek,rtl9300-snand.yaml   | 58 
>>>> +++++++++++++++++++
>>>>   1 file changed, 58 insertions(+)
>>>>   create mode 100644 
>>>> Documentation/devicetree/bindings/spi/realtek,rtl9300-snand.yaml
>>>>
>>>> diff --git 
>>>> a/Documentation/devicetree/bindings/spi/realtek,rtl9300-snand.yaml 
>>>> b/Documentation/devicetree/bindings/spi/realtek,rtl9300-snand.yaml
>>>> new file mode 100644
>>>> index 000000000000..c66aea24cb35
>>>> --- /dev/null
>>>> +++ b/Documentation/devicetree/bindings/spi/realtek,rtl9300-snand.yaml
>>>> @@ -0,0 +1,58 @@
>>>> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
>>>> +%YAML 1.2
>>>> +---
>>>> +$id: http://devicetree.org/schemas/spi/realtek,rtl9300-snand.yaml#
>>>> +$schema: http://devicetree.org/meta-schemas/core.yaml#
>>>> +
>>>> +title: SPI-NAND Flash Controller for Realtek RTL9300 SoCs
>>>> +
>>>> +maintainers:
>>>> +  - Chris Packham <chris.packham@...iedtelesis.co.nz>
>>>> +
>>>> +description:
>>>> +  The Realtek RTL9300 SoCs have a built in SPI-NAND controller. It 
>>>> supports
>>>> +  typical SPI-NAND page cache operations in single, dual or quad IO 
>>>> mode.
>>>> +
>>>> +properties:
>>>> +  compatible:
>>>> +    items:
>>> Why 9300 cannot be alone? What does 9300 mean even? Wildcards and family
>>> models are not allowed in general.
>>
>> The main thing about the RTL9300 is that that is what all the Realtek 
>> documents use to refer to these chips and the specific numbers are 
>> akin to the manufacturing part number that you'd actually order (maybe 
>> that's a bit of a stretch).
>>
>> The SoC/CPU block probably does exist as a separate silicon die that 
>> they connect to the different switch blocks in the chips that they 
>> sell but I don't think you can get "just" the SoC. There is every 
>> chance that we'll see that same SoC/CPU block pop up in new chips (I 
>> see references to a RTL9302D in some documents). I'd like to be able 
>> to support these chips using "rtl9300" but if that's violating the 
>> wildcard rule I can drop it.
>>
> Maybe it's helpful to think of the RTL9300 as the IP block that is 
> integrated into the RTL9301, RTL9302B, etc.

Yeah, it could work but we discourage this pattern. New devices from
930x might not be compatible with 9300 and then it is unclear what
"9300" actually mean.

The generic recommendation: please go with specific compatibles and use
one specific compatible as fallback for others.

Best regards,
Krzysztof