linux-kernel - Re: [PATCH 1/2] dt-bindings: cpufreq: Introduce QCOM CPUFREQ Firmware bindings

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Date:   Thu, 25 Oct 2018 15:43:39 -0700
From:   Matthias Kaehlcke <mka@...omium.org>
To:     Amit Kucheria <amit.kucheria@...aro.org>
Cc:     Taniya Das <tdas@...eaurora.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux PM list <linux-pm@...r.kernel.org>,
        Stephen Boyd <sboyd@...nel.org>,
        Rajendra Nayak <rnayak@...eaurora.org>,
        DTML <devicetree@...r.kernel.org>, Rob Herring <robh@...nel.org>,
        Saravana Kannan <skannan@...eaurora.org>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>, evgreen@...gle.com
Subject: Re: [PATCH 1/2] dt-bindings: cpufreq: Introduce QCOM CPUFREQ
 Firmware bindings

Hi,

On Tue, Oct 23, 2018 at 05:23:34PM +0530, Amit Kucheria wrote:
> Hi Taniya,
> 
> Both the patches are missing v9 in their subject line - this threw off
> patchwork when trying to download the patches.
> 
> On Thu, Oct 11, 2018 at 5:06 PM Taniya Das <tdas@...eaurora.org> wrote:
> >
> > Add QCOM cpufreq firmware device bindings for Qualcomm Technology Inc's
> > SoCs. This is required for managing the cpu frequency transitions which are
> > controlled by the hardware engine.
> 
> I tested these patches on the sdm845-mtp against 4.19 and found that
> the frequency gets stuck at the highest opp (the boost frequency)
> after running a couple of 'yes > /dev/null &' instances. Have you
> tested these against a mainline kernel?
> 
> See cpufreq statistics below:
> 
> linaro-test [rc=0]# cat policy?/scaling_cur_freq
> 300000
> 2803200
> 
> linaro-test [rc=0]# cat policy?/stats/time_in_state
> 300000 100840
> 403200 388
> 480000 71
> 576000 54
> 652800 22
> 748800 11
> 825600 5
> 902400 5
> 979200 9
> 1056000 3
> 1132800 2
> 1228800 5
> 1324800 8
> 1420800 2
> 1516800 1
> 1612800 0
> 1689600 0
> 1766400 392
> 825600 22048
> 902400 21
> 979200 4
> 1056000 15
> 1209600 6
> 1286400 0
> 1363200 1
> 1459200 0
> 1536000 0
> 1612800 1
> 1689600 0
> 1766400 0
> 1843200 2
> 1920000 2
> 1996800 0
> 2092800 0
> 2169600 0
> 2246400 0
> 2323200 0
> 2400000 0
> 2476800 0
> 2553600 0
> 2649600 0
> 2707200 0
> 2764800 0
> 2784000 0
> 2803200 79718

I can repro this on SDM845 with a v4.19 kernel.

Since the little cores don't have a boost frequency I think maxing out
can be expected with a high workload and no thermal throttling.
However the big cores have a boost frequency (2.803 MHz), so the
driver shouldn't be stuck at it. Though in practice I also wonder if
the ~1% 'boost' makes a big difference in terms of performance or CPU
overload ...

Cheers

Matthias