linux-kernel - Re: Nokia N900: Proper C-states

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Message-ID: <56BA1C92.4040202@linaro.org>
Date:	Tue, 9 Feb 2016 18:06:26 +0100
From:	Daniel Lezcano <daniel.lezcano@...aro.org>
To:	Tony Lindgren <tony@...mide.com>
Cc:	Pali Rohár <pali.rohar@...il.com>,
	Jean Pihet <j-pihet@...com>,
	Santosh Shilimkar <santosh.shilimkar@...com>,
	Kevin Hilman <khilman@...com>, Nishanth Menon <nm@...com>,
	Pavel Machel <pavel@....cz>,
	Aaro Koskinen <aaro.koskinen@....fi>,
	Sebastian Reichel <sre@...nel.org>,
	Ivaylo Dimitrov <ivo.g.dimitrov.75@...il.com>,
	linux-omap@...r.kernel.org, linux-kernel@...r.kernel.org,
	Lorenzo Pieralisi <Lorenzo.Pieralisi@....com>
Subject: Re: Nokia N900: Proper C-states

On 02/09/2016 04:56 PM, Tony Lindgren wrote:
> * Daniel Lezcano <daniel.lezcano@...aro.org> [160102 14:01]:
>> On 01/02/2016 03:26 PM, Pali Rohár wrote:
>>> Hello,
>>>
>>> due to this Daniel Lezcano commit (ARM: OMAP3: cpuidle - remove rx51
>>> cpuidle parameters table)
>>>
>>> https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=231900afba52d6faddfb480cde4132d4edc089bc
>>>
>>> we need patch cpuidle34xx.c code to fix commit for Nokia N900. See:
>>>
>>> https://github.com/pali/linux-n900/commit/e147fd4b678f1f3d7a5235287910960bd41e04dc
>>>
>>> As Nokia N900 code is converting from legacy board code to DST, I would
>>> like to know how to patch correctly omap3_idle_driver in DTS with
>>> correct values measured for Nokia N900. Thanks!
>
> I'm almost certain those values are not n900 specific but should be
> used for omap3430 in general.
>
>> the conversion to the DT based arm cpuidle driver could be a bit complex
>> with one issue (index 0 != cpu_do_idle()) and one performance regression
>> (cpu_pm_enter/exit will be called in retention mode, even if this is not
>> needed).
>>
>> It will result in a PM code only on one side and on the other side, the
>> generic cpuidle-arm.c driver will be used instead with the DT definition. It
>> is worth to the conversion because the result will be nice IMO.
>>
>> Added Lorenzo who is initially author of the arm generic driver. We already
>> discussed in the past about those two issues above and I think this is
>> something we should improve.
>
> While this conversion process is going on, we could just add
> omap3430_idle_driver and set that based on cpu_is_omap3430()
> in omap3_idle_init().

Yes, that could be a temporary alternative.




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