linux-kernel - Re: [Letux-kernel] [RFC PATCH 0/3] Enable 1GHz support on omap36xx

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Message-Id: <D3E8B5DC-AB53-4F46-8ABB-F839A11EB31C@goldelico.com>
Date:   Wed, 11 Sep 2019 19:43:16 +0200
From:   "H. Nikolaus Schaller" <hns@...delico.com>
To:     Adam Ford <aford173@...il.com>
Cc:     Nishanth Menon <nm@...com>,
        Linux-OMAP <linux-omap@...r.kernel.org>,
        Tony Lindgren <tony@...mide.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        André Roth <neolynx@...il.com>,
        Discussions about the Letux Kernel 
        <letux-kernel@...nphoenux.org>
Subject: Re: [Letux-kernel] [RFC PATCH 0/3] Enable 1GHz support on omap36xx

Hi Adam,

> Am 11.09.2019 um 18:01 schrieb H. Nikolaus Schaller <hns@...delico.com>:
> 
>> 
>> Am 11.09.2019 um 17:56 schrieb Adam Ford <aford173@...il.com>:
>> 
>>> There are some subtleties for testing.
>>> 
>>> * I have added turbo-mode; to OPP6 / OPP1G
>>> * which means they are available but not used by the ondemand govenor
>>> * to enable them one has to echo 1 >/sys/devices/system/cpu/cpufreq/boost
>> 
>> Will that be documented somewhere? If not, can we put a comment in the
>> device tree so people know how to enable it?
> 
> It seems to be pretty standard on i86 systems if you google for "turbo mode".
> I have added it to the commit message which adds the vbb regulator.

And, I am not sure if DT maintainers will accept comments about the
Linux /sys implementation in device tree files or bindings. Those
should be independent of Linux.

Basically the turbo-mode property is a hint to the OPP system (which
may or may not use of it).

So I think it is indeed better to have it in the commit message and
not the code.

One more thought: as long as we do not have junction temperature monitoring
we should keep it off by default... We may even remove the turbo-mode
designator if we have the 90°C limit and smart reflex working.

BR,
Nikolaus