linux-kernel - Re: [PATCH v3 04/17] dt-bindings: soc: mobileye: add EyeQ5 OLB system controller

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Message-ID: <9a5f017c-530c-482b-9cbf-a07281e92589@ti.com>
Date: Thu, 25 Jan 2024 08:33:53 -0600
From: Andrew Davis <afd@...com>
To: Théo Lebrun <theo.lebrun@...tlin.com>,
        Krzysztof
 Kozlowski <krzysztof.kozlowski@...aro.org>,
        Rob Herring <robh@...nel.org>
CC: Gregory CLEMENT <gregory.clement@...tlin.com>,
        Michael Turquette
	<mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>,
        Krzysztof
 Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley
	<conor+dt@...nel.org>,
        Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        Linus
 Walleij <linus.walleij@...aro.org>,
        Rafał Miłecki
	<rafal@...ecki.pl>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Vladimir
 Kondratiev <vladimir.kondratiev@...ileye.com>,
        <linux-mips@...r.kernel.org>, <linux-clk@...r.kernel.org>,
        <devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        Thomas Petazzoni
	<thomas.petazzoni@...tlin.com>,
        Tawfik Bayouk <tawfik.bayouk@...ileye.com>,
        <linux-gpio@...r.kernel.org>
Subject: Re: [PATCH v3 04/17] dt-bindings: soc: mobileye: add EyeQ5 OLB system
 controller

On 1/25/24 5:01 AM, Théo Lebrun wrote:
> Hello,
> 
> On Thu Jan 25, 2024 at 8:51 AM CET, Krzysztof Kozlowski wrote:
>> On 24/01/2024 16:14, Rob Herring wrote:
>>>> +
>>>> +      pinctrl-b {
>>>> +        compatible = "mobileye,eyeq5-b-pinctrl";
>>>> +        #pinctrl-cells = <1>;
>>>> +      };
>>>> +    };
>>>
>>> This can all be simplified to:
>>>
>>> system-controller@...000 {
>>>      compatible = "mobileye,eyeq5-olb", "syscon";
>>>      reg = <0xe00000 0x400>;
>>>      #reset-cells = <2>;
>>>      #clock-cells = <1>;
>>>      clocks = <&xtal>;
>>>      clock-names = "ref";
>>>
>>>      pins { ... };
>>> };
>>>
>>> There is no need for sub nodes unless you have reusable blocks or each
>>> block has its own resources in DT.
>>
>> Yes, however I believe there should be resources here: each subnode
>> should get its address space. This is a bit tied to implementation,
>> which currently assumes "everyone can fiddle with everything" in this block.
>>
>> Theo, can you draw memory map?
> 
> It would be a mess. I've counted things up. The first 147 registers are
> used in this 0x400 block. There are 31 individual blocks, with 7
> registers unused (holes to align next block).
> 
> Functions are reset, clocks, LBIST, MBIST, DDR control, GPIO,
> accelerator control, CPU entrypoint, PDTrace, IRQs, chip info & ID
> stuff, control registers for PCIe / eMMC / Eth / SGMII / DMA / etc.
> 
> Some will never get used from Linux, others might. Maybe a moderate
> approach would be to create ressources for major blocks and make it
> evolve organically, without imposing that all uses lead to a new
> ressource creation.
> 

That is usually how nodes are added to DT. If you modeled this
system-controller space as a "simple-bus" instead of a "syscon"
device, you could add nodes as you implement them. Rather than
all at once as you have to by treating this space as one large
blob device.

Andrew

> Thanks,
> 
> --
> Théo Lebrun, Bootlin
> Embedded Linux and Kernel engineering
> https://bootlin.com
>