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Date: Mon, 15 Apr 2024 16:08:42 +0200
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Subject: Re: [RFC PATCH v2 30/31] kvx: Add power controller driver
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To: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>, Yann Sionneau
 <ysionneau@kalray.eu>, Arnd Bergmann <arnd@arndb.de>, Jonathan Corbet
 <corbet@lwn.net>, Thomas Gleixner <tglx@linutronix.de>, Marc Zyngier
 <maz@kernel.org>, Rob Herring <robh+dt@kernel.org>, Krzysztof Kozlowski
 <krzysztof.kozlowski+dt@linaro.org>, Will Deacon <will@kernel.org>, Peter
 Zijlstra <peterz@infradead.org>, Boqun Feng <boqun.feng@gmail.com>, Mark
 Rutland <mark.rutland@arm.com>, Eric Biederman <ebiederm@xmission.com>, Kees
 Cook <keescook@chromium.org>, Oleg Nesterov <oleg@redhat.com>, Ingo Molnar
 <mingo@redhat.com>, Waiman Long <longman@redhat.com>, "Aneesh Kumar K.V"
 <aneesh.kumar@linux.ibm.com>, Andrew Morton <akpm@linux-foundation.org>,
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 Albert Ou <aou@eecs.berkeley.edu>, Jules Maselbas <jmaselbas@kalray.eu>,
 Guillaume Thouvenin <gthouvenin@kalray.eu>, Clement Leger
 <clement@clement-leger.fr>, Vincent Chardon
 <vincent.chardon@elsys-design.com>, Marc =?utf-8?b?UG91bGhpw6hz?=
 <dkm@kataplop.net>, Julian Vetter <jvetter@kalray.eu>, Samuel Jones
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 <lmichel@kalray.eu>, Louis Morhet <lmorhet@kalray.eu>, Julien Hascoet
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 Bibo Mao <maobibo@loongson.cn>, Atish Patra <atishp@atishpatra.org>, "Jason
 A. Donenfeld" <Jason@zx2c4.com>, Qi Liu <liuqi115@huawei.com>, Jiaxun Yang
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 Brown <broonie@kernel.org>, Janosch Frank <frankja@linux.ibm.com>, Alexey
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Cc: Benjamin Mugnier <mugnier.benjamin@gmail.com>,
 linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org,
 devicetree@vger.kernel.org, linux-mm@kvack.org, linux-arch@vger.kernel.org,
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References: <20230120141002.2442-1-ysionneau@kalray.eu>
 <20230120141002.2442-31-ysionneau@kalray.eu>
 <f69adaf2-6582-c134-5671-4d6fd100fcf1@linaro.org>
From: Yann Sionneau <ysionneau@kalrayinc.com>
In-Reply-To: <f69adaf2-6582-c134-5671-4d6fd100fcf1@linaro.org>
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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@kalray.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