linux-kernel - Re: [PATCH v2 2/4] firmware: arm_scmi: Add machine_allowlist and machine

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Message-ID: <20250212062542.GA15796@localhost.localdomain>
Date: Wed, 12 Feb 2025 14:25:42 +0800
From: Peng Fan <peng.fan@....nxp.com>
To: Sudeep Holla <sudeep.holla@....com>
Cc: Peng Fan <peng.fan@....com>,
	Cristian Marussi <cristian.marussi@....com>,
	Saravana Kannan <saravanak@...gle.com>,
	Linus Walleij <linus.walleij@...aro.org>,
	Aisheng Dong <aisheng.dong@....com>,
	Fabio Estevam <festevam@...il.com>, Shawn Guo <shawnguo@...nel.org>,
	Jacky Bai <ping.bai@....com>,
	Pengutronix Kernel Team <kernel@...gutronix.de>,
	Sascha Hauer <s.hauer@...gutronix.de>,
	"arm-scmi@...r.kernel.org" <arm-scmi@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" <linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
	"imx@...ts.linux.dev" <imx@...ts.linux.dev>
Subject: Re: [PATCH v2 2/4] firmware: arm_scmi: Add machine_allowlist and
 machine_blocklist

On Tue, Feb 11, 2025 at 03:46:36PM +0000, Sudeep Holla wrote:
>On Mon, Feb 10, 2025 at 01:19:14PM +0000, Peng Fan wrote:
>> 
>> I just have a prototype and tested on i.MX95.
>
>You didn't answer me @[1]. How can we disable it for perf/cpufreq if there
>are users already. I will look at the code once I am convince we can do that.
>For now, I am not. I am worried we may break some platform.

The only user in upstream kernel with using the dummy clock is juno-scmi.dtsi.

SCMI_PROTOCOL_PERF is used by two drivers cpufreq-scmi.c, scmi_perf_domain.c.

In cpufreq-scmi.c a dummy clock proviver is created, the gpu node in juno-scmi.dtsi
takes "<&scmi_dvfs 2>" into clocks property. I think this is wrong.

Why not use scmi_clk node? cpufreq created clk provider should only be limited
for cpu device which will not be impacted by fwdevlink.

If wanna to tune gpu performance, the power-domains property should be used,
not clocks property.

It is the juno-scmi.dtsi should be fixed.

If juno-scmi.dtsi will keep as it is, please suggest possible solution
on fixing the issue.

Regards,
Peng

>
>-- 
>Regards,
>Sudeep
>
>[1] https://lore.kernel.org/all/20241227151306.jh2oabc64xd54dms@bogus