linux-kernel - Re: [PATCH] ARM64: dts: meson-gxbb-odroidc2: Disable SCPI DVFS

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Message-ID: <9f508097-f605-ebd8-20af-c3e798c6fdcc@poczta.onet.pl>
Date:   Thu, 5 Jan 2017 20:04:03 +0100
From:   Michał Zegan <webczat_200@...zta.onet.pl>
To:     Neil Armstrong <narmstrong@...libre.com>, khilman@...libre.com,
        carlo@...one.org
Cc:     linux-amlogic@...ts.infradead.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH] ARM64: dts: meson-gxbb-odroidc2: Disable SCPI DVFS

Hello.

The patch causes cpufreq module (scpi-cpufreq) not to detect cpufreq, so
it actually works, but...
Loading the module causes few errors because of not found frequencies or
something, then it is all okay. However after loading scpi-cpufreq you
cannot actually power the cpu off and on. You will power it off
successfully, but when trying to power it on, the cpufreq driver will
error out, and then after it happens, the cpu that was trying to go
online will be offline again, and that is a little... unfortunate. The
question is, and I cannot really test that: will the module actually
autoload after this change?

W dniu 05.01.2017 o 16:02, Neil Armstrong pisze:
> The current hardware is not able to run with all cores enabled at a
> cluster frequency superior at 1536MHz.
> But the currently shipped u-boot for the platform still reports an OPP
> table with possible DVFS frequency up to 2GHz, and will not change since
> the off-tree linux tree supports limiting the OPPs with a kernel parameter.
> A recent u-boot change reports the boot-time DVFS around 100MHz and
> the default performance cpufreq governor sets the maximum frequency.
> Previous version of u-boot reported to be already at the max OPP and
> left the OPP as is.
> Nevertheless, other governors like ondemand could setup the max frequency
> and make the system crash.
> 
> This patch disables the DVFS clock and disables cpufreq.
> 
> Fixes: 70db166a2baa ("ARM64: dts: meson-gxbb: Add SCPI with cpufreq & sensors Nodes")
> Signed-off-by: Neil Armstrong <narmstrong@...libre.com>
> ---
>  arch/arm64/boot/dts/amlogic/meson-gxbb-odroidc2.dts | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/arch/arm64/boot/dts/amlogic/meson-gxbb-odroidc2.dts b/arch/arm64/boot/dts/amlogic/meson-gxbb-odroidc2.dts
> index 238fbea..5e63e3b 100644
> --- a/arch/arm64/boot/dts/amlogic/meson-gxbb-odroidc2.dts
> +++ b/arch/arm64/boot/dts/amlogic/meson-gxbb-odroidc2.dts
> @@ -137,6 +137,10 @@
>  	};
>  };
>  
> +&scpi_dvfs {
> +	status = "disabled";
> +};
> +
>  &uart_AO {
>  	status = "okay";
>  	pinctrl-0 = <&uart_ao_a_pins>;
> 



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