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

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Date:   Fri, 9 Sep 2022 10:49:27 +0300
From:   Serge Semin <fancer.lancer@...il.com>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
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 Tue, Aug 30, 2022 at 06:01:56PM +0300, Krzysztof Kozlowski wrote:
> 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)?

As we agreed my device will have dedicated DT-schema referencing this
one. The DT-bindings in the subject is the generic IP-core bindings.
So some of the lines indeed may be absent depending on the synthesize
parameters or the particular platform specifics. My device DT-schema
will contain more specific clocks/resets/irqs properties constraints.

> 
> > 
> >>
> >>> +
> >>> +  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.

I'll replace the number 4 with the IRQ-level triggered macro and drop
the flag 0 then.

-Sergey

> 
> Best regards,
> Krzysztof