[PATCH] arm64: dts: meson: remove CPU opps below 1GHz for G12B/SM1

[Neil Armstrong]

On 09/02/2022 14:55, Christian Hewitt wrote:
> Amlogic G12B and SM1 devices experience CPU stalls and random board
> wedges when the system idles and CPU cores clock down to lower opp
> points. Recent vendor kernels include a change to remove 100-250MHz
> (with no explanation) [0] but other downstream sources also remove
> the 500/667MHz points (also with no explanation). Unless 100-667Mhz
> opps are removed or the CPU governor forced to performance, stalls
> are observed, so let's remove them an improve stability/uptime.
> 
> [0] https://github.com/khadas/linux/commit/20e237a4fe9f0302370e24950cb1416e038eee03
> 
> Signed-off-by: Christian Hewitt <christianshewitt at gmail.com>
> ---
> Numerous people have experienced this issue and I have tested with
> only the low opp-points removed and numerous voltage tweaks: but it
> makes no difference. With the opp points present an Odroid N2 or
> Khadas VIM3 reliably drop off my network after being left idling
> overnight with UART showing a CPU stall splat. With the opp points
> removed I see weeks of uninterupted uptime. It's beyond my skills
> to research what the cause of the stalls might be, but if anyone
> ever figures it out we can always restore things. NB: This issue
> is not too widely reported in forums, but that's largely because
> most of the Amlogic supporting distros have been including this
> change picked from my kernel patchset for some time.
> 
>   .../boot/dts/amlogic/meson-g12b-a311d.dtsi    | 40 -------------------
>   .../boot/dts/amlogic/meson-g12b-s922x.dtsi    | 40 -------------------
>   arch/arm64/boot/dts/amlogic/meson-sm1.dtsi    | 20 ----------
>   3 files changed, 100 deletions(-)
> 
> diff --git a/arch/arm64/boot/dts/amlogic/meson-g12b-a311d.dtsi b/arch/arm64/boot/dts/amlogic/meson-g12b-a311d.dtsi
> index d61f43052a34..8e9ad1e51d66 100644
> --- a/arch/arm64/boot/dts/amlogic/meson-g12b-a311d.dtsi
> +++ b/arch/arm64/boot/dts/amlogic/meson-g12b-a311d.dtsi
> @@ -11,26 +11,6 @@
>   		compatible = "operating-points-v2";
>   		opp-shared;
>   
> -		opp-100000000 {
> -			opp-hz = /bits/ 64 <100000000>;
> -			opp-microvolt = <731000>;
> -		};
> -
> -		opp-250000000 {
> -			opp-hz = /bits/ 64 <250000000>;
> -			opp-microvolt = <731000>;
> -		};
> -
> -		opp-500000000 {
> -			opp-hz = /bits/ 64 <500000000>;
> -			opp-microvolt = <731000>;
> -		};
> -
> -		opp-667000000 {
> -			opp-hz = /bits/ 64 <667000000>;
> -			opp-microvolt = <731000>;
> -		};
> -
>   		opp-1000000000 {
>   			opp-hz = /bits/ 64 <1000000000>;
>   			opp-microvolt = <761000>;
> @@ -71,26 +51,6 @@
>   		compatible = "operating-points-v2";
>   		opp-shared;
>   
> -		opp-100000000 {
> -			opp-hz = /bits/ 64 <100000000>;
> -			opp-microvolt = <731000>;
> -		};
> -
> -		opp-250000000 {
> -			opp-hz = /bits/ 64 <250000000>;
> -			opp-microvolt = <731000>;
> -		};
> -
> -		opp-500000000 {
> -			opp-hz = /bits/ 64 <500000000>;
> -			opp-microvolt = <731000>;
> -		};
> -
> -		opp-667000000 {
> -			opp-hz = /bits/ 64 <667000000>;
> -			opp-microvolt = <731000>;
> -		};
> -
>   		opp-1000000000 {
>   			opp-hz = /bits/ 64 <1000000000>;
>   			opp-microvolt = <731000>;
> diff --git a/arch/arm64/boot/dts/amlogic/meson-g12b-s922x.dtsi b/arch/arm64/boot/dts/amlogic/meson-g12b-s922x.dtsi
> index 1e5d0ee5d541..44c23c984034 100644
> --- a/arch/arm64/boot/dts/amlogic/meson-g12b-s922x.dtsi
> +++ b/arch/arm64/boot/dts/amlogic/meson-g12b-s922x.dtsi
> @@ -11,26 +11,6 @@
>   		compatible = "operating-points-v2";
>   		opp-shared;
>   
> -		opp-100000000 {
> -			opp-hz = /bits/ 64 <100000000>;
> -			opp-microvolt = <731000>;
> -		};
> -
> -		opp-250000000 {
> -			opp-hz = /bits/ 64 <250000000>;
> -			opp-microvolt = <731000>;
> -		};
> -
> -		opp-500000000 {
> -			opp-hz = /bits/ 64 <500000000>;
> -			opp-microvolt = <731000>;
> -		};
> -
> -		opp-667000000 {
> -			opp-hz = /bits/ 64 <667000000>;
> -			opp-microvolt = <731000>;
> -		};
> -
>   		opp-1000000000 {
>   			opp-hz = /bits/ 64 <1000000000>;
>   			opp-microvolt = <731000>;
> @@ -76,26 +56,6 @@
>   		compatible = "operating-points-v2";
>   		opp-shared;
>   
> -		opp-100000000 {
> -			opp-hz = /bits/ 64 <100000000>;
> -			opp-microvolt = <751000>;
> -		};
> -
> -		opp-250000000 {
> -			opp-hz = /bits/ 64 <250000000>;
> -			opp-microvolt = <751000>;
> -		};
> -
> -		opp-500000000 {
> -			opp-hz = /bits/ 64 <500000000>;
> -			opp-microvolt = <751000>;
> -		};
> -
> -		opp-667000000 {
> -			opp-hz = /bits/ 64 <667000000>;
> -			opp-microvolt = <751000>;
> -		};
> -
>   		opp-1000000000 {
>   			opp-hz = /bits/ 64 <1000000000>;
>   			opp-microvolt = <771000>;
> diff --git a/arch/arm64/boot/dts/amlogic/meson-sm1.dtsi b/arch/arm64/boot/dts/amlogic/meson-sm1.dtsi
> index 3c07a89bfd27..80737731af3f 100644
> --- a/arch/arm64/boot/dts/amlogic/meson-sm1.dtsi
> +++ b/arch/arm64/boot/dts/amlogic/meson-sm1.dtsi
> @@ -95,26 +95,6 @@
>   		compatible = "operating-points-v2";
>   		opp-shared;
>   
> -		opp-100000000 {
> -			opp-hz = /bits/ 64 <100000000>;
> -			opp-microvolt = <730000>;
> -		};
> -
> -		opp-250000000 {
> -			opp-hz = /bits/ 64 <250000000>;
> -			opp-microvolt = <730000>;
> -		};
> -
> -		opp-500000000 {
> -			opp-hz = /bits/ 64 <500000000>;
> -			opp-microvolt = <730000>;
> -		};
> -
> -		opp-667000000 {
> -			opp-hz = /bits/ 64 <666666666>;
> -			opp-microvolt = <750000>;
> -		};
> -
>   		opp-1000000000 {
>   			opp-hz = /bits/ 64 <1000000000>;
>   			opp-microvolt = <770000>;

Can you find if an acceptable set of Fixes tag can be added to permit backporting to the current LTS kernels ?

Neil