linux-kernel - Re: [PATCH v1 1/5] dt-bindings: cpufreq: Add binding for NVIDIA Tegra20/30

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Message-ID: <4b0966fa-c3f1-b7c9-e4bd-24337b8e97fe@gmail.com>
Date:   Wed, 17 Oct 2018 15:42:50 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Jon Hunter <jonathanh@...dia.com>,
        Thierry Reding <thierry.reding@...il.com>,
        Peter De Schrijver <pdeschrijver@...dia.com>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Rob Herring <robh+dt@...nel.org>
Cc:     linux-pm@...r.kernel.org, devicetree@...r.kernel.org,
        linux-tegra@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 1/5] dt-bindings: cpufreq: Add binding for NVIDIA
 Tegra20/30

On 10/17/18 3:37 PM, Dmitry Osipenko wrote:
> On 10/17/18 11:40 AM, Jon Hunter wrote:
>>
>> On 30/08/2018 20:43, Dmitry Osipenko wrote:
>>> Add device-tree binding that describes CPU frequency-scaling hardware
>>> found on NVIDIA Tegra20/30 SoC's.
>>>
>>> Signed-off-by: Dmitry Osipenko <digetx@...il.com>
>>> ---
>>>  .../cpufreq/nvidia,tegra20-cpufreq.txt        | 38 +++++++++++++++++++
>>>  1 file changed, 38 insertions(+)
>>>  create mode 100644 Documentation/devicetree/bindings/cpufreq/nvidia,tegra20-cpufreq.txt
>>>
>>> diff --git a/Documentation/devicetree/bindings/cpufreq/nvidia,tegra20-cpufreq.txt b/Documentation/devicetree/bindings/cpufreq/nvidia,tegra20-cpufreq.txt
>>> new file mode 100644
>>> index 000000000000..2c51f676e958
>>> --- /dev/null
>>> +++ b/Documentation/devicetree/bindings/cpufreq/nvidia,tegra20-cpufreq.txt
>>> @@ -0,0 +1,38 @@
>>> +Binding for NVIDIA Tegra20 CPUFreq
>>> +==================================
>>> +
>>> +Required properties:
>>> +- clocks: Must contain an entry for each entry in clock-names.
>>> +  See ../clocks/clock-bindings.txt for details.
>>> +- clock-names: Must include the following entries:
>>> +  - pll_x: main-parent for CPU clock, must be the first entry
>>> +  - backup: intermediate-parent for CPU clock
>>> +  - cpu: the CPU clock
>>
>> Is it likely that 'backup' will be anything other that pll_p? If not why
>> not just call it pll_p? Personally, I don't 'backup' to descriptive even
>> though I can see what you mean.
>>
>> I can see that you want to make this flexible, but if the likelihood is
>> that we will just use pll_p then I am not sure it is warranted at this
>> point.
> 
> That won't describe HW, but software. And device tree should describe HW.
> 

Though indeed it is unlikely that anything else other than pll_p will be used, so it is a software/firmware description anyway.