linux-kernel - Re: [PATCH] DT: rockchip: Fix stability issues with the 'performance' governor on rock960

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Message-ID: <20181016142138.GA24727@mani>
Date:   Tue, 16 Oct 2018 19:51:38 +0530
From:   Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
To:     Daniel Lezcano <daniel.lezcano@...aro.org>
Cc:     heiko@...ech.de, linux-kernel@...r.kernel.org,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Vicente Bergas <vicencb@...il.com>,
        Shawn Lin <shawn.lin@...k-chips.com>,
        Ezequiel Garcia <ezequiel@...labora.com>,
        Enric Balletbo i Serra <enric.balletbo@...labora.com>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        "moderated list:ARM/Rockchip SoC support" 
        <linux-arm-kernel@...ts.infradead.org>,
        "open list:ARM/Rockchip SoC support" 
        <linux-rockchip@...ts.infradead.org>
Subject: Re: [PATCH] DT: rockchip: Fix stability issues with the
 'performance' governor on rock960

On Tue, Oct 16, 2018 at 04:00:20PM +0200, Daniel Lezcano wrote:
> When the performance governor is set as default, the rock960 hangs
> around one minute after booting, whatever the activity is (idle, key
> pressed, loaded, ...).
> 
> Based on the commit log found at https://patchwork.kernel.org/patch/10092377/
> 
> "vdd_log has no consumer and therefore will not be set to a specific
> voltage. Still the PWM output pin gets configured and thence the vdd_log
> output voltage will changed from it's default. Depending on the idle
> state of the PWM this will slightly over or undervoltage the logic supply
> of the RK3399 and cause instability with GbE (undervoltage) and PCIe
> (overvoltage). Since the default value set by a voltage divider is the
> correct supply voltage and we don't need to change it during runtime we
> remove the rail from the devicetree completely so the PWM pin will not
> be configured."
> 
> After removing the vdd-log from the rock960's specific DT, the board
> does no longer hang and shows a stable behavior.
> 
> Apply the same change for the rock960 by removing the vdd-log from the
> DT.
> 
> Signed-off-by: Daniel Lezcano <daniel.lezcano@...aro.org>

Tested on Rock960 v1.2 board, hence

Tested-by: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>

Thanks a ton!

Regards,
Mani

> ---
>  arch/arm64/boot/dts/rockchip/rk3399-rock960.dtsi | 12 ------------
>  1 file changed, 12 deletions(-)
> 
> diff --git a/arch/arm64/boot/dts/rockchip/rk3399-rock960.dtsi b/arch/arm64/boot/dts/rockchip/rk3399-rock960.dtsi
> index 6c8c4ab..56abbb0 100644
> --- a/arch/arm64/boot/dts/rockchip/rk3399-rock960.dtsi
> +++ b/arch/arm64/boot/dts/rockchip/rk3399-rock960.dtsi
> @@ -57,18 +57,6 @@
>  		regulator-always-on;
>  		vin-supply = <&vcc_sys>;
>  	};
> -
> -	vdd_log: vdd-log {
> -		compatible = "pwm-regulator";
> -		pwms = <&pwm2 0 25000 0>;
> -		regulator-name = "vdd_log";
> -		regulator-min-microvolt = <800000>;
> -		regulator-max-microvolt = <1400000>;
> -		regulator-always-on;
> -		regulator-boot-on;
> -		vin-supply = <&vcc_sys>;
> -	};
> -
>  };
>  
>  &cpu_l0 {
> -- 
> 2.7.4
>