linux-kernel - Re: [PATCH 5/8] OPP: Allow multiple clocks for a device

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Message-ID: <20220630095245.otvo53ezd4avoujw@vireshk-i7>
Date:   Thu, 30 Jun 2022 15:22:45 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     Dmitry Osipenko <dmitry.osipenko@...labora.com>
Cc:     Jon Hunter <jonathanh@...dia.com>,
        Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
        Viresh Kumar <vireshk@...nel.org>, Nishanth Menon <nm@...com>,
        Stephen Boyd <sboyd@...nel.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>, linux-pm@...r.kernel.org,
        Vincent Guittot <vincent.guittot@...aro.org>,
        linux-kernel@...r.kernel.org,
        "linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>
Subject: Re: [PATCH 5/8] OPP: Allow multiple clocks for a device

On 30-06-22, 12:13, Dmitry Osipenko wrote:
> On 6/30/22 03:50, Viresh Kumar wrote:
> > On 29-06-22, 21:33, Dmitry Osipenko wrote:
> >> Today I noticed that tegra30-devfreq driver now fails to probe because
> >> dev_pm_opp_find_freq_ceil() fails with -ERANGE. This patch is guilty for
> >> that. Could you please take a look?
 
> We added memory interconnect support to Tegra and since that time only
> the memory controller can drive the clock rate. All other drivers,
> including the devfreq, now issue memory bandwidth requests using ICC.
> 
> In case of the devfreq driver, it's the OPP core that makes the bw
> request using ICC.
> 
> But it's the set_freq_table() that fails [2], I see
> dev_pm_opp_get_opp_count() returns 17, which is correct, and then
> dev_pm_opp_find_freq_ceil(freq=0) returns freq=1, which shall be
> freq=12750000.

I am confused, you said earlier that it is failing with -ERANGE, but
now it is a bad freq value ?

Which one of these it is ?

The problem I see is here though, because of which I was asking you
the question earlier:

- tegra30-devfreq driver calls devm_pm_opp_of_add_table_noclk(), i.e.
  clk_count == 0.

- _read_rate() (in drivers/opp/of.c) skips reading any opp-hz
  properties if clk_count is 0.

- And so you can get -ERANGE or some other error.

Can you please see where we are failing. Also I don't see how freq can
get set to 1 currently.

-- 
viresh