linux-kernel - Re: [PATCH v7 2/4] dt-bindings: clock: sophgo: support SG2042

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Date: Sat, 13 Jan 2024 09:15:41 +0800
From: Chen Wang <unicorn_wang@...look.com>
To: Samuel Holland <samuel.holland@...ive.com>,
 Conor Dooley <conor@...nel.org>
Cc: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
 Chen Wang <unicornxw@...il.com>, aou@...s.berkeley.edu, chao.wei@...hgo.com,
 krzysztof.kozlowski+dt@...aro.org, mturquette@...libre.com,
 palmer@...belt.com, paul.walmsley@...ive.com, richardcochran@...il.com,
 robh+dt@...nel.org, sboyd@...nel.org, devicetree@...r.kernel.org,
 linux-clk@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-riscv@...ts.infradead.org, haijiao.liu@...hgo.com,
 xiaoguang.xing@...hgo.com, guoren@...nel.org, jszhang@...nel.org,
 inochiama@...look.com, Conor Dooley <conor.dooley@...rochip.com>
Subject: Re: [PATCH v7 2/4] dt-bindings: clock: sophgo: support SG2042


On 2024/1/13 3:35, Samuel Holland wrote:
> Hi Conor, Chen,
>
> On 2024-01-11 10:58 AM, Conor Dooley wrote:
>> On Thu, Jan 11, 2024 at 04:00:04PM +0800, Chen Wang wrote:
>>> With this change, we describe the plls defined in system control as pllclk,
>>> as a child node of system controller. clkgen will use pllclk as "input"
>>> because pll clocks are parent of div clocks .
>>>
>>> But there is another remaining question about the gate clock. For those gate
>>> clocks controlled by CLOCK, no problem we will provide then in clkgen, but
>>> for those gate clocks controlled by registers in SYS_CTRL, they are child
>>> gate of the "clk_gate_rp_cpu_normal", which is a gate clock provided by
>>> clkgen. If I extracted those SYS_CTRL gate clocks and define them in system
>>> controller dts node, I may have to use "clk_gate_rp_cpu_normal" as their
>>> input, it looks a bit wierd becasue there are cases where each other serves
>>> as input. I try to draft below DTS to explan what I meant. I'm not sure if
>>> it can work and I'd love to hear your guidance.
>> I'm not sure how this sort of circular relationship works for probing
>> works either. Stephen etc would know more than me here.
> It generally works fine. The common clock framework can handle the child clock
> being registered before its parent, even when using a DT (fw_name) reference.
> See for example clk_core_fill_parent_index() and
> clk_core_reparent_orphans_nolock() in drivers/clk/clk.c
Learned and thank you.
>
> Regards,
> Samuel
>