linux-kernel - Re: [PATCH v1 3/5] ARM: tegra: Create tegra20-cpufreq device on Tegra30

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Date:   Wed, 17 Oct 2018 15:02:25 +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 3/5] ARM: tegra: Create tegra20-cpufreq device on
 Tegra30

On 10/17/18 12:54 PM, Jon Hunter wrote:
> 
> On 17/10/2018 09:49, Jon Hunter wrote:
>>
>> On 30/08/2018 20:43, Dmitry Osipenko wrote:
>>> Tegra20-cpufreq driver require a platform device in order to be loaded,
>>> instantiate a simple platform device for the driver during of the machines
>>> late initialization. Driver now supports Tegra30 SoC's, hence create the
>>> device on Tegra30 machines.
>>>
>>> Signed-off-by: Dmitry Osipenko <digetx@...il.com>
>>> ---
>>>  arch/arm/mach-tegra/tegra.c | 4 ++++
>>>  1 file changed, 4 insertions(+)
>>>
>>> diff --git a/arch/arm/mach-tegra/tegra.c b/arch/arm/mach-tegra/tegra.c
>>> index 67d8ae60ac67..b559e22eab76 100644
>>> --- a/arch/arm/mach-tegra/tegra.c
>>> +++ b/arch/arm/mach-tegra/tegra.c
>>> @@ -111,6 +111,10 @@ static void __init tegra_dt_init_late(void)
>>>  	if (IS_ENABLED(CONFIG_ARCH_TEGRA_2x_SOC) &&
>>>  	    of_machine_is_compatible("nvidia,tegra20"))
>>>  		platform_device_register_simple("tegra20-cpufreq", -1, NULL, 0);
>>> +
>>> +	if (IS_ENABLED(CONFIG_ARCH_TEGRA_3x_SOC) &&
>>> +	    of_machine_is_compatible("nvidia,tegra30"))
>>> +		platform_device_register_simple("tegra20-cpufreq", -1, NULL, 0);
>>>  }
>>>  
>>>  static const char * const tegra_dt_board_compat[] = {
>>
>> Not sure why you would do this if now the driver only works with DT. Am
>> I missing something?
> 
> Actually, not sure why we just don't move this into the actual driver
> itself like we have for tegra124.

Tegra124 has specific HW for the CPUFreq, T20/30 do not. Hence on T20/30 CPUFreq control is implemented purely in software and there is no real HW device for the driver.