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Date: Thu, 02 Apr 2015 22:35:15 +0300
From: Adrian Hunter <adrian.hunter@intel.com>
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To: Len Brown <lenb@kernel.org>
CC: Ulf Hansson <ulf.hansson@linaro.org>,
        linux-mmc <linux-mmc@vger.kernel.org>,
        "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>,
        Len Brown <len.brown@intel.com>, Pavel Machek <pavel@ucw.cz>,
        Kevin Hilman <khilman@linaro.org>,
        Tomeu Vizoso <tomeu.vizoso@collabora.com>,
        Linux PM list <linux-pm@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [RFC PATCH 0/4] mmc: sdhci: Support maximum DMA latency request
 via PM QoS
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On 1/04/2015 10:59 p.m., Len Brown wrote:
>> Ad hoc testing with Lenovo Thinkpad 10 showed a stress
>> test could run for at least 24 hours with the patches,
>> compared to less than an hour without.
>
> There is a patch in linux-next to delete C1E from BYT,
> since it is problematic on multiple platforms.
> I don't suppose that just disabling that state without disabling C6
> is sufficient to fix the Thinkpad 10?  (I'm betting not, but
> it can't hurt to try -- you can use the "disable" attribute for the state
> in /sys/devices/system/cpu/cpu*/cpuidle/stateN)
>
> I think your choice of the PM_QOS sub-system here is the right one,
> and that your selection of 20usec threshold is also a good choice
> for what you want to do -- though on non-intel_idle machine somplace,
> there may be some ACPI BIOS _CST with random number for C6 latency.
>
> It would be interesting to see how your C6 residency (turbostat
> --debug will show this to you)
> and your battery life are changed by disabling C6 during MMC activity.

I will do some more testing as you suggest, although it will have to
wait until next week due to Easter holidays here.