linux-kernel - Re: [PATCH 01/13] dt-bindings: memory: snps: Extend schema with IRQs/resets/clocks props

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Message-ID: <3bb4b2c9-de07-f981-14bd-02c58c9fad35@linaro.org>
Date:   Tue, 30 Aug 2022 18:01:56 +0300
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To:     Serge Semin <fancer.lancer@...il.com>
Cc:     Serge Semin <Sergey.Semin@...kalelectronics.ru>,
        Michal Simek <michal.simek@...inx.com>,
        Borislav Petkov <bp@...en8.de>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Tony Luck <tony.luck@...el.com>,
        Rob Herring <robh+dt@...nel.org>,
        Manish Narani <manish.narani@...inx.com>,
        Alexey Malahov <Alexey.Malahov@...kalelectronics.ru>,
        Michail Ivanov <Michail.Ivanov@...kalelectronics.ru>,
        Pavel Parkhomenko <Pavel.Parkhomenko@...kalelectronics.ru>,
        Punnaiah Choudary Kalluri 
        <punnaiah.choudary.kalluri@...inx.com>,
        Dinh Nguyen <dinguyen@...nel.org>,
        James Morse <james.morse@....com>,
        Robert Richter <rric@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-edac@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 01/13] dt-bindings: memory: snps: Extend schema with
 IRQs/resets/clocks props

On 26/08/2022 11:47, Serge Semin wrote:

>>
>>> +
>>> +  interrupt-names:
>>> +    minItems: 1
>>> +    maxItems: 5
>>> +    oneOf:
>>> +      - description: Common ECC CE/UE/Scrubber/DFI Errors IRQ
>>> +        items:
>>> +          - const: ecc
>>> +      - description: Individual ECC CE/UE/Scrubber/DFI Errors IRQs
>>> +        items:
>>> +          enum: [ ecc_ce, ecc_ue, ecc_ap, ecc_sbr, dfi_e ]
>>>  
>>>    reg:
>>>      maxItems: 1
>>>  
>>> +  clocks:
>>> +    description:
>>> +      A standard set of the clock sources contains CSRs bus clock, AXI-ports
>>> +      reference clock, DDRC core clock, Scrubber standalone clock
>>> +      (synchronous to the DDRC clock).
>>> +    minItems: 1
>>> +    maxItems: 4
>>
> 
>> I expect list to be strictly defined, not flexible.
> 
> Some of the clock sources might be absent or tied up to another one
> (for instance pclk, aclk and sbr can be clocked from a single core
> clock source). It depends on the IP-core synthesize parameters.

Yet still your device has clock lines - clock inputs, right? Therefore
still 4 clocks will be going there or you want to say that the pin is
not connected (or pulled down)?

> 
>>
>>> +
>>> +  clock-names:
>>> +    minItems: 1
>>> +    maxItems: 4
>>> +    items:
>>> +      enum: [ pclk, aclk, core, sbr ]
>>> +
>>> +  resets:
>>> +    description:
>>> +      Each clock domain can have separate reset signal.
>>> +    minItems: 1
>>> +    maxItems: 4
>>> +
>>> +  reset-names:
>>> +    minItems: 1
>>> +    maxItems: 4
>>> +    items:
>>> +      enum: [ prst, arst, core, sbr ]
>>
> 
>> The same.
> 
> The same as for the clock.
> 
>>
>>> +
>>>  required:
>>>    - compatible
>>>    - reg
>>> @@ -48,4 +92,15 @@ examples:
>>>        interrupt-parent = <&gic>;
>>>        interrupts = <0 112 4>;
>>>      };
>>> +  - |
>>> +    memory-controller@...70000 {
>>> +      compatible = "snps,ddrc-3.80a";
>>> +      reg = <0x3d400000 0x400000>;
>>> +
>>> +      interrupts = <0 147 4>, <0 148 4>, <0 149 4>, <0 150 4>;
>>
> 
>> Use proper defines.
> 
> What do you mean? Which defines do you think would be proper? If you
> meant the IRQ DT-bindings macros, then what difference does it make
> for a generic device in the DT-binding example? 

The macros/defines representing these numbers.


> Note since the device
> is defined as generic it can be placed on different platforms with
> different interrupt controller requirements. So what do you mean by
> "proper" in this case?

Proper means text instead of hard-coded number. This piece of code has
meaning in a specific context, because you used interrupts matching some
specific interrupt controllers. In that controller context, the "4" has
a meaning. Just like "0". You cannot say that this piece of code is
interrupt-controller-independent, because it is not. 4 has meaning.

If you want it to be independent, drop all the flags... If you use flags
from a specific implementation, then use proper defines matching them,
not hard-coded numbers.

Best regards,
Krzysztof