Message-ID: <626a079e-9640-b358-a452-6b226a619f34@microchip.com>
Date:   Mon, 27 Jun 2022 11:03:02 +0000
From:   <Conor.Dooley@...rochip.com>
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        <damien.lemoal@...nsource.wdc.com>, <robh+dt@...nel.org>,
        <krzysztof.kozlowski+dt@...aro.org>
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Subject: Re: [PATCH 07/14] riscv: dts: canaan: fix the k210's memory node

On 27/06/2022 10:24, Krzysztof Kozlowski wrote:
> EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
> 
> On 27/06/2022 09:06, Conor.Dooley@...rochip.com wrote:
>>
>>
>> On 27/06/2022 07:55, Krzysztof Kozlowski wrote:
>>> On 21/06/2022 11:49, Conor.Dooley@...rochip.com wrote:
>>>> On 20/06/2022 01:25, Damien Le Moal wrote:
>>>>> EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
>>>>>
>>>>> On 6/20/22 08:54, Conor.Dooley@...rochip.com wrote:
>>>>>> On 20/06/2022 00:38, Damien Le Moal wrote:
>>>>>>> EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
>>>>>>>
>>>>>>> On 6/18/22 21:30, Conor Dooley wrote:
>>>>>>>> From: Conor Dooley <conor.dooley@...rochip.com>
>>>>>>>>
>>>>>>>> The k210 memory node has a compatible string that does not match with
>>>>>>>> any driver or dt-binding & has several non standard properties.
>>>>>>>> Replace the reg names with a comment and delete the rest.
>>>>>>>>
>>>>>>>> Signed-off-by: Conor Dooley <conor.dooley@...rochip.com>
>>>>>>>> ---
>>>>>>>> ---
>>>>>>>>     arch/riscv/boot/dts/canaan/k210.dtsi | 6 ------
>>>>>>>>     1 file changed, 6 deletions(-)
>>>>>>>>
>>>>>>>> diff --git a/arch/riscv/boot/dts/canaan/k210.dtsi b/arch/riscv/boot/dts/canaan/k210.dtsi
>>>>>>>> index 44d338514761..287ea6eebe47 100644
>>>>>>>> --- a/arch/riscv/boot/dts/canaan/k210.dtsi
>>>>>>>> +++ b/arch/riscv/boot/dts/canaan/k210.dtsi
>>>>>>>> @@ -69,15 +69,9 @@ cpu1_intc: interrupt-controller {
>>>>>>>>
>>>>>>>>          sram: memory@...00000 {
>>>>>>>>                  device_type = "memory";
>>>>>>>> -             compatible = "canaan,k210-sram";
>>>>>>>>                  reg = <0x80000000 0x400000>,
>>>>>>>>                        <0x80400000 0x200000>,
>>>>>>>>                        <0x80600000 0x200000>;
>>>>>>>> -             reg-names = "sram0", "sram1", "aisram";
>>>>>>>> -             clocks = <&sysclk K210_CLK_SRAM0>,
>>>>>>>> -                      <&sysclk K210_CLK_SRAM1>,
>>>>>>>> -                      <&sysclk K210_CLK_AI>;
>>>>>>>> -             clock-names = "sram0", "sram1", "aisram";
>>>>>>>>          };
>>>>>>>
>>>>>>> These are used by u-boot to setup the memory clocks and initialize the
>>>>>>> aisram. Sure the kernel actually does not use this, but to be in sync with
>>>>>>> u-boot DT, I would prefer keeping this as is. Right now, u-boot *and* the
>>>>>>> kernel work fine with both u-boot internal DT and the kernel DT.
>>>>>>
>>>>>> Right, but unfortunately that desire alone doesn't do anything about
>>>>>> the dtbs_check complaints.
>>>>>>
>>>>>> I guess the alternative approach of actually documenting the compatible
>>>>>> would be more palatable?
>>>>>
>>>>> Yes, I think so. That would allow keeping the fields without the DTB build
>>>>> warnings.
>>>>
>>>> Hmm looks like that approach contradicts the dt-schema;
>>>> https://github.com/devicetree-org/dt-schema/blob/main/dtschema/schemas/memory.yaml
>>>>
>>>> @Rob,Krzysztof what is one meant to do here?
>>>
>>> Why do you think it contradict bindings? Bindings for memory allow
>>
>> Because when I tried to write the binding, the memory node complained
>> about the clock properties etc and referenced the dt-schema (which
>> for memory@foo nodes has additionalProperties: false.
> 
> Ah, I see, I looked at wrong level. Indeed memory node cannot have
> anything else.
> 
>>
>>> additional properties, so you just need to create binding for this one.
>>> And make it a correct binding, IOW, be sure that these clocks are real etc.
>>>
>>> Although usually we had separate bindings (and device drivers) for
>>> memory controllers, instead of including them in the "memory" node.
>>
>> I guess changing to that format would probably require some changes on
>> the U-Boot side of things. Taking "calxeda,hb-ddr-ctrl" as an example,
>> looks like the clocks etc go in a controller node, which seems like a
>> "better" way of doing it -
> 
> Yes, because I think memory node is kind of special. It describes the
> physical memory layout for the system, not the memory controller or
> memory characteristics (like timings).
> 
> What U-Boot needs is indeed memory controller node. It's not only
> calxeda but also few others using JEDEC LPDDR bindings.
> 
>> but would break existing dts in U-Boot
>> without changes to handle both methods there.
> 
> Yes, that's a bit inconvenient but also a price someone has to pay for
> introducing DTS properties without bindings.
> 

Alright so, I'll make it a memory controller and conjure up a v2.
As always, thanks for your help Krzysztof!

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