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References: <20191101143126.2549-1-linux.amoon@gmail.com> <7hfthtrvvv.fsf@baylibre.com>
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From:   Anand Moon <linux.amoon@gmail.com>
Date:   Tue, 10 Dec 2019 20:20:05 +0530
Message-ID: <CANAwSgQx3LjQe60TGgKyk6B5BD5y1caS2tA+O+GFES7=qCFeKg@mail.gmail.com>
Subject: Re: [RFC-next 0/1] Odroid C2: Enable DVFS for cpu
To:     Neil Armstrong <narmstrong@baylibre.com>
Cc:     Kevin Hilman <khilman@baylibre.com>,
        Rob Herring <robh+dt@kernel.org>,
        Martin Blumenstingl <martin.blumenstingl@googlemail.com>,
        Jerome Brunet <jbrunet@baylibre.com>,
        devicetree <devicetree@vger.kernel.org>,
        linux-arm-kernel <linux-arm-kernel@lists.infradead.org>,
        linux-amlogic@lists.infradead.org,
        Linux Kernel <linux-kernel@vger.kernel.org>
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Hi Neil / Kevin,

On Tue, 10 Dec 2019 at 14:13, Neil Armstrong <narmstrong@baylibre.com> wrote:
>
> On 09/12/2019 23:12, Kevin Hilman wrote:
> > Anand Moon <linux.amoon@gmail.com> writes:
> >
> >> Some how this patch got lost, so resend this again.
> >>
> >> [0] https://patchwork.kernel.org/patch/11136545/
> >>
> >> This patch enable DVFS on GXBB Odroid C2.
> >>
> >> DVFS has been tested by running the arm64 cpuburn
> >> [1] https://github.com/ssvb/cpuburn-arm/blob/master/cpuburn-a53.S
> >> PM-QA testing
> >> [2] https://git.linaro.org/power/pm-qa.git [cpufreq testcase]
> >>
> >> Tested on latest U-Boot 2019.07-1 (Aug 01 2019 - 23:58:01 +0000) Arch Linux ARM
> >
> > Have you tested with the Harkernel u-boot?
> >
> > Last I remember, enabling CPUfreq will cause system hangs with the
> > Hardkernel u-boot because of improperly enabled frequencies, so I'm not
> > terribly inclined to merge this patch.

HK u-boot have many issue with loading the kernel, with load address
*it's really hard to build the kernel for HK u-boot*,
to get the configuration correctly.

Well I have tested with mainline u-boot with latest ATF .
I would prefer mainline u-boot for all the Amlogic SBC, since
they sync with latest driver changes.

>
> Same, since the bootloader boots with the max supported freq of the board,
> there is not real need of DVFS except for specific low-power use-cases.
>
> And still, some early boards still use the bad SCPI freq table, we can't break them.
>
> Neil
>
I will leave this to your expert domain knowledge if you want to
enable this now.

Here is output of on the latest kernel.
*cpupower*
#  cpupower frequency-info
analyzing CPU 0:
  driver: scpi-cpufreq
  CPUs which run at the same hardware frequency: 0 1 2 3
  CPUs which need to have their frequency coordinated by software: 0 1 2 3
  maximum transition latency: 200 us
  hardware limits: 100.0 MHz - 1.54 GHz
  available frequency steps:  100.0 MHz, 250 MHz, 500 MHz, 1000 MHz,
1.30 GHz, 1.54 GHz
  available cpufreq governors: conservative ondemand userspace
powersave performance schedutil
  current policy: frequency should be within 100.0 MHz and 100.0 MHz.
                  The governor "ondemand" may decide which speed to use
                  within this range.
  current CPU frequency: 100.0 MHz (asserted by call to hardware)

*powertop*
# powertop
            Package |            CPU 0
 100 MHz    47.1%   |  100 MHz    41.5%
 250 MHz     0.0%   |  250 MHz     0.0%
 500 MHz     0.0%   |  500 MHz     0.0%
1000 MHz     0.0%   | 1000 MHz     0.0%
1296 MHz     0.0%   | 1296 MHz     0.0%
1.54 GHz     0.0%   | 1.54 GHz     0.0%
Idle        52.9%   | Idle        58.5%

> >
> >> Patch based on my next-20191031 for 5.5.x kernel.
> >> Hope this is not late entry.
> >
> > Re: "too late".  FYI... when you post things as RFC, it means you're
> > looking for comments (Request For Comment) but that it's not intended
> > for merging.

Ok  thanks for this input.

> >
> > I didn't see any comments on this, but I also didn't see a non-RFC
> > follow-up, so I didn't queue it for v5.5.
No problem.
> >
> > Kevin
> >
>
-Anand