linux-kernel - Re: [PATCH v6 51/52] PM / devfreq: tegra30: Support interconnect and OPPs from device-tree

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Message-ID: <d8803971-1af7-0934-3f4c-8a9222623957@gmail.com>
Date:   Mon, 2 Nov 2020 22:58:18 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     cwchoi00@...il.com
Cc:     Thierry Reding <thierry.reding@...il.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Georgi Djakov <georgi.djakov@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>,
        Peter De Schrijver <pdeschrijver@...dia.com>,
        MyungJoo Ham <myungjoo.ham@...sung.com>,
        Kyungmin Park <kyungmin.park@...sung.com>,
        Chanwoo Choi <cw00.choi@...sung.com>,
        Mikko Perttunen <cyndis@...si.fi>,
        Viresh Kumar <vireshk@...nel.org>,
        Peter Geis <pgwipeout@...il.com>,
        Nicolas Chauvet <kwizart@...il.com>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        linux-tegra@...r.kernel.org,
        Linux PM list <linux-pm@...r.kernel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        devicetree <devicetree@...r.kernel.org>
Subject: Re: [PATCH v6 51/52] PM / devfreq: tegra30: Support interconnect and
 OPPs from device-tree

01.11.2020 18:57, Chanwoo Choi пишет:
> On Mon, Nov 2, 2020 at 12:49 AM Dmitry Osipenko <digetx@...il.com> wrote:
>>
>> 01.11.2020 18:44, Chanwoo Choi пишет:
>>>> OPP core will try to grab the clock reference for the table and it may
>>>> cause EPROBE_DEFER. Although, it shouldn't happen here because we have
>>>> devm_clk_get() before the get_opp_table(), hence seems the deferred
>>>> probe indeed shouldn't happen in this case.
>>> It is my missing point. If there, you're right.
>>> Could you provide the code point to check the clock reference on the OPP core?
>>
>> Please see it here:
>>
>> https://elixir.bootlin.com/linux/v5.10-rc1/source/drivers/opp/core.c#L1101
> 
> Thanks. It seems that if device tree node contains the any node,
> it is not EPROBE_DEFER because of just using "clk_get(dev, NULL)".
> 
> The patch[1] used the 'dev_err_probe' for getting the "emc" clock.
> Do you need to check it more?
> 
> [1] https://git.kernel.org/pub/scm/linux/kernel/git/chanwoo/linux.git/commit/?h=devfreq-next&id=09d56d92ad25b58113f4ec677e9b1ac1e2c3072b

It should be safe to assume that the EPROBE_DEFER won't happen for
dev_pm_opp_get_opp_table(). I'll improve it in v7, thanks.