linux-kernel - Re: [PATCH] OPP: Fix support for required OPPs for multiple PM domains

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Message-ID: <20240718030556.dmgzs24d2bk3hmpb@vireshk-i7>
Date: Thu, 18 Jul 2024 08:35:56 +0530
From: Viresh Kumar <viresh.kumar@...aro.org>
To: Ulf Hansson <ulf.hansson@...aro.org>
Cc: Viresh Kumar <vireshk@...nel.org>, Nishanth Menon <nm@...com>,
	Stephen Boyd <sboyd@...nel.org>, Nikunj Kela <nkela@...cinc.com>,
	Prasad Sodagudi <psodagud@...cinc.com>, linux-pm@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	linux-tegra@...r.kernel.org, stable@...r.kernel.org
Subject: Re: [PATCH] OPP: Fix support for required OPPs for multiple PM
 domains

On 11-07-24, 17:25, Ulf Hansson wrote:
> Right, I get your point.
> 
> Although, it seems to me that just limiting required-opps to
> performance-levels, could avoid us from having to enforce the OPPs for
> genpd. In other words, doing something along the lines of $subject
> patch should work fine.

I really don't want to design the code that way. Required OPPs don't
have anything to do with a genpd. Genpd is just one of the possible
use cases and I would like the code to reflect it, even if we don't
have any other users for this kind of stuff for now, but we surely
can. Just that those problems are solved differently for now. For
example, cache DVFS along with CPUs, etc.

And as I said earlier, it is entirely possible that the genpd OPP
table wants to configure few more things apart from just level, and
hence a full fledged set-opp is a better design choice.

> In fact, it looks to me that the required-opps handling for the
> *single* PM domain case, is already limited to solely
> performance-levels (opp-level), as there are no required_devs being
> assigned for it. Or did I get that wrong?

That's why the API for setting required-opps was introduced, to make
it a central point of entry for all use cases where we want to attach
a device.

-- 
viresh