linux-kernel - Re: [PATCH V2 00/13] OPP: Add support for multiple clocks*

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Date:   Tue, 12 Jul 2022 13:22:40 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     Johan Hovold <johan@...nel.org>
Cc:     Bjorn Andersson <bjorn.andersson@...aro.org>,
        Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>,
        Chanwoo Choi <cw00.choi@...sung.com>,
        Dmitry Osipenko <digetx@...il.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Kyungmin Park <kyungmin.park@...sung.com>,
        MyungJoo Ham <myungjoo.ham@...sung.com>,
        Nishanth Menon <nm@...com>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Stephen Boyd <sboyd@...nel.org>,
        Thierry Reding <thierry.reding@...il.com>,
        Viresh Kumar <vireshk@...nel.org>, linux-pm@...r.kernel.org,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
        devicetree@...r.kernel.org,
        Dmitry Osipenko <dmitry.osipenko@...labora.com>,
        linux-kernel@...r.kernel.org, linux-tegra@...r.kernel.org,
        Rob Herring <robh@...nel.org>
Subject: Re: [PATCH V2 00/13] OPP: Add support for multiple clocks*

On 11-07-22, 18:40, Johan Hovold wrote:
> This break OPP parsing on SC8280XP and hence cpufreq and other things:
> 
> [  +0.010890] cpu cpu0: _opp_add_static_v2: opp key field not found
> [  +0.000019] cpu cpu0: _of_add_opp_table_v2: Failed to add OPP, -19
> [  +0.000060] cpu cpu0: _opp_is_duplicate: duplicate OPPs detected. Existing: freq: 300000000, volt: 576000, enabled: 1. New: freq: 403200000, volt: 576000, enabled: 1
> [  +0.000030] cpu cpu0: _opp_is_duplicate: duplicate OPPs detected. Existing: freq: 300000000, volt: 576000, enabled: 1. New: freq: 499200000, volt: 576000, enabled: 1
> ...
> 
> I just did a rebase on next-20220708 and hit this.
> 
> I've narrowed it down to _read_rate() now returning -ENODEV since
> opp_table->clk_count is zero.
> 
> Similar to what was reported for tegra for v1:
> 
> 	https://lore.kernel.org/all/58cc8e3c-74d4-e432-8502-299312a1f15e@collabora.com/
> 
> I don't have time to look at this any more today, but it would we nice
> if you could unbreak linux-next.
> 
> Perhaps Bjorn or Mani can help with further details, but this doesn't
> look like something that is specific to SC8280XP.

It is actually. This is yet another corner case, Tegra had one as
well.

I have tried to understand the Qcom code / setup to best of my
abilities, and the problem as per me is that qcom-cpufreq-hw doesn't
provide a clk to the OPP core, which breaks it after the new updates
to the OPP core. I believe following will solve it. Can someone please
try this ? I will then merge it with the right commit.

diff --git a/drivers/opp/core.c b/drivers/opp/core.c
index 666e1ebf91d1..4f4a285886fa 100644
--- a/drivers/opp/core.c
+++ b/drivers/opp/core.c
@@ -1384,6 +1384,20 @@ static struct opp_table *_update_opp_table_clk(struct device *dev,
        }

        if (ret == -ENOENT) {
+               /*
+                * There are few platforms which don't want the OPP core to
+                * manage device's clock settings. In such cases neither the
+                * platform provides the clks explicitly to us, nor the DT
+                * contains a valid clk entry. The OPP nodes in DT may still
+                * contain "opp-hz" property though, which we need to parse and
+                * allow the platform to find an OPP based on freq later on.
+                *
+                * This is a simple solution to take care of such corner cases,
+                * i.e. make the clk_count 1, which lets us allocate space for
+                * frequency in opp->rates and also parse the entries in DT.
+                */
+               opp_table->clk_count = 1;
+
                dev_dbg(dev, "%s: Couldn't find clock: %d\n", __func__, ret);
                return opp_table;
        }

-- 
viresh