Re: [RFC PATCH v4 1/4] cpuidle: Add time keeping and irq enabling

From: Colin Cross <ccross@google.com>
To: "Turquette, Mike" <mturquette@ti.com>
Cc: Robert Lee <rob.lee@linaro.org>,
	nicolas.pitre@linaro.org, linaro-dev@lists.linaro.org,
	nicolas.ferre@atmel.com, linux@arm.linux.org.uk, khilman@ti.com,
	kgene.kim@samsung.com, daniel.lezcano@linaro.org,
	magnus.damm@gmail.com, linux-acpi@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org, patches@linaro.org,
	arnd.bergmann@linaro.org, len.brown@intel.com,
	linux-pm@vger.kernel.org, nsekhar@ti.com, s.hauer@pengutronix.de,
	Baohua.Song@csr.com, vincent.guittot@linaro.org,
	linux@maxim.org.za, shawn.guo@freescale.com,
	deepthi@linux.vnet.ibm.com, broonie@opensource.wolfsonmicro.com,
	amit.kucheria@linaro.org, amit.kachhap@linaro.org
Subject: Re: [RFC PATCH v4 1/4] cpuidle: Add time keeping and irq enabling
Date: Sat, 4 Feb 2012 17:36:05 -0800	[thread overview]
Message-ID: <CAMbhsRR2Zsv7d+_iganMhz5WxDiUYd-zOCoVehz4yjzyH2q+wA@mail.gmail.com> (raw)
In-Reply-To: <CAJOA=zOhKtt5GohHfYp6=xVTODR2a_RGkDNTwozbusrBSsqE+w@mail.gmail.com>

On Sat, Feb 4, 2012 at 2:06 PM, Turquette, Mike <mturquette@ti.com> wrote:
> On Sat, Feb 4, 2012 at 11:02 AM, Colin Cross <ccross@google.com> wrote:
>> What's the point of the pre_enter call?  This seems very similar to
>> the prepare call that was removed in 3.2.  Drivers can already demote
>
> Hi Colin,
>
> I asked Rob to re-introduce the .prepare callback (not .pre_enter).
>
> The short version of why I requested this is so that I can experiment
> with modifying wake-up latency and theshold values dynamically based
> on PM QoS constraints.  For an OMAP-specific example, I'd like to see
> our C-states no longer model both MPU and CORE power domains, and
> instead only model the MPU.  Then when entering idle the PM QoS
> constraints against the CORE power domain's wake-up latency can be
> considered in the .prepare callback which will affect the C-state
> parameters as well as program the CORE low power target state.

prepare makes sense to adjust latencies, as long as it is not used for
state demotion as well.

> .pre_enter isn't really right for the above case so I'm happy for it
> to be dropped, but I'll probably re-introduce something like .prepare
> in the future...
>
> Regards,
> Mike
>
>> the target state in their enter call.  The only thing you do between
>> pre_enter and enter is trace and account for the time.  Is there some
>> long call you don't want included in the idle time?  Some
>> documentation would help, and you need to very clearly define the
>> semantics of when post_enter gets called when pre_enter or enter
>> return errors.
>>
>> _______________________________________________
>> linux-arm-kernel mailing list
>> linux-arm-kernel@lists.infradead.org
>> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
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