linux-kernel - Re: [PATCH 5/5] OPP: Remove custom OPP helper support

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Date:   Mon, 27 Jun 2022 12:49:37 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     Dmitry Osipenko <digetx@...il.com>
Cc:     Keerthy <j-keerthy@...com>, Dave Gerlach <d-gerlach@...com>,
        Viresh Kumar <vireshk@...nel.org>, Nishanth Menon <nm@...com>,
        Stephen Boyd <sboyd@...nel.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Thierry Reding <thierry.reding@...il.com>,
        linux-pm@...r.kernel.org,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
        linux-kernel@...r.kernel.org,
        "linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>
Subject: Re: [PATCH 5/5] OPP: Remove custom OPP helper support

On 27-06-22, 10:09, Dmitry Osipenko wrote:
> Yes, I missed that multi-clock OPP patch, thanks.
> 
> Seems _opp_compare_key() won't work properly for the multi-clocks since
> Tegra doesn't have bandwidth nor level for the 3d OPPs. Why does it need
> to check opp_table->clk_count == 1? Shouldn't it be opp_table->clk_count
> > 0?

The problem is that when we have multiple clocks, we can't assume any
of them as primary. Its the combination of the clock frequencies that
make them unique. Otherwise, what will happen if we have same
frequency of the first clock in two OPPs, but different frequency of
the second clock.

Because of this, we won't also support multiple clocks in all freq
finder APIs, like dev_pm_opp_find_freq_exact(). We can't do that from
just one frequency.

Ideally, the drivers should now be calling dev_pm_opp_set_opp() to set
the OPP now.

For your case, I think you can just add levels (like index) in the OPP
table. So we can uniquely identify each OPP.

-- 
viresh