linux-kernel - Re: [RFC PATCH v2 30/31] kvx: Add power controller driver

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Date: Mon, 15 Apr 2024 16:08:42 +0200
From: Yann Sionneau <ysionneau@...rayinc.com>
To: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>, Yann Sionneau
 <ysionneau@...ray.eu>, Arnd Bergmann <arnd@...db.de>, Jonathan Corbet
 <corbet@....net>, Thomas Gleixner <tglx@...utronix.de>, Marc Zyngier
 <maz@...nel.org>, Rob Herring <robh+dt@...nel.org>, Krzysztof Kozlowski
 <krzysztof.kozlowski+dt@...aro.org>, Will Deacon <will@...nel.org>, Peter
 Zijlstra <peterz@...radead.org>, Boqun Feng <boqun.feng@...il.com>, Mark
 Rutland <mark.rutland@....com>, Eric Biederman <ebiederm@...ssion.com>, Kees
 Cook <keescook@...omium.org>, Oleg Nesterov <oleg@...hat.com>, Ingo Molnar
 <mingo@...hat.com>, Waiman Long <longman@...hat.com>, "Aneesh Kumar K.V"
 <aneesh.kumar@...ux.ibm.com>, Andrew Morton <akpm@...ux-foundation.org>,
 Nick Piggin <npiggin@...il.com>, Paul Moore <paul@...l-moore.com>, Eric
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 Walmsley <paul.walmsley@...ive.com>, Palmer Dabbelt <palmer@...belt.com>,
 Albert Ou <aou@...s.berkeley.edu>, Jules Maselbas <jmaselbas@...ray.eu>,
 Guillaume Thouvenin <gthouvenin@...ray.eu>, Clement Leger
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 <dkm@...aplop.net>, Julian Vetter <jvetter@...ray.eu>, Samuel Jones
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Cc: Benjamin Mugnier <mugnier.benjamin@...il.com>,
 linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
 devicetree@...r.kernel.org, linux-mm@...ck.org, linux-arch@...r.kernel.org,
 linux-audit@...hat.com, linux-riscv@...ts.infradead.org, bpf@...r.kernel.org
Subject: Re: [RFC PATCH v2 30/31] kvx: Add power controller driver

Hello Krzysztof, Arnd, all,

On 1/22/23 12:54, Krzysztof Kozlowski wrote:
> On 20/01/2023 15:10, Yann Sionneau wrote:
>> From: Jules Maselbas <jmaselbas@...ray.eu>
>>
>> The Power Controller (pwr-ctrl) control cores reset and wake-up
>> procedure.
>> +
>> +int __init kvx_pwr_ctrl_probe(void)
>> +{
>> +	struct device_node *ctrl;
>> +
>> +	ctrl = get_pwr_ctrl_node();
>> +	if (!ctrl) {
>> +		pr_err("Failed to get power controller node\n");
>> +		return -EINVAL;
>> +	}
>> +
>> +	if (!of_device_is_compatible(ctrl, "kalray,kvx-pwr-ctrl")) {
>> +		pr_err("Failed to get power controller node\n");
> No. Drivers go to drivers, not to arch directory. This should be a
> proper driver instead of some fake stub doing its own driver matching.
> You need to rework this.

I am working on a v3 patchset, therefore I am working on a solution for 
this "pwr-ctrl" driver that needs to go somewhere else than arch/kvx/.

The purpose of this "driver" is just to expose a void 
kvx_pwr_ctrl_cpu_poweron(unsigned int cpu) function, used by 
kernel/smpboot.c function __cpu_up() in order to start secondary CPUs in 
SMP config.

Doing this, on our SoC, requires writing 3 registers in a memory-mapped 
device named "power controller".

I made some researches in drivers/ but I am not sure yet what's a good 
place that fits what our device is doing (booting secondary CPUs).

* drivers/power/reset seems to be for resetting the entire SoC

* drivers/power/supply seems to be to control power supplies ICs/periph.

* drivers/reset seems to be for device reset

* drivers/pmdomain maybe ?

* drivers/soc ?

* drivers/platform ?

* drivers/misc ?

What do you think?

Thanks.

Regards,

-- 

Yann