linux-kernel - Re: [PATCH 4/5] arm64: dts: allwinner: Add sun4i MMIO timer nodes

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Date:   Mon, 15 Mar 2021 19:32:20 +0100
From:   Jernej Škrabec <jernej.skrabec@...l.net>
To:     Daniel Lezcano <daniel.lezcano@...aro.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Rob Herring <robh+dt@...nel.org>,
        Maxime Ripard <mripard@...nel.org>,
        Chen-Yu Tsai <wens@...e.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Samuel Holland <samuel@...lland.org>
Cc:     devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, Samuel Holland <samuel@...lland.org>
Subject: Re: [PATCH 4/5] arm64: dts: allwinner: Add sun4i MMIO timer nodes

Hi!

Dne ponedeljek, 15. marec 2021 ob 05:32:49 CET je Samuel Holland napisal(a):
> For a CPU to enter an idle state, there must be some timer which can
> trigger an IRQ to wake it back up. The local ARM architectural timer is
> not sufficient, because that timer stops when the CPU is powered down.
> Some other CPU's ARM architectural timer can be used, but this prevents
> that other CPU from entering an idle state. So to allow all CPUs to
> enter an idle state at the same time, some MMIO timer must be available
> that is not tied to any CPU.
> 
> The basic "sun4i" timer seems most appropriate for this purpose due to
> its moderate rate, balancing precision and power consumption.
> 
> Signed-off-by: Samuel Holland <samuel@...lland.org>
> ---
>  arch/arm64/boot/dts/allwinner/sun50i-a64.dtsi  | 9 +++++++++
>  arch/arm64/boot/dts/allwinner/sun50i-h6.dtsi   | 9 +++++++++
>  arch/arm64/boot/dts/allwinner/sun50i-h616.dtsi | 9 +++++++++
>  3 files changed, 27 insertions(+)
> 
> diff --git a/arch/arm64/boot/dts/allwinner/sun50i-a64.dtsi
> b/arch/arm64/boot/dts/allwinner/sun50i-a64.dtsi index
> 33df866f6ea9..64e8b4a372cc 100644
> --- a/arch/arm64/boot/dts/allwinner/sun50i-a64.dtsi
> +++ b/arch/arm64/boot/dts/allwinner/sun50i-a64.dtsi
> @@ -905,6 +905,15 @@ uart4_rts_cts_pins: uart4-rts-cts-pins {
>  			};
>  		};
> 
> +		timer@...0c00 {
> +			compatible = "allwinner,sun50i-a64-timer",
> +				     "allwinner,sun8i-a23-timer";
> +			reg = <0x01c20c00 0xa0>;
> +			interrupts = <GIC_SPI 18 
IRQ_TYPE_LEVEL_HIGH>,
> +				     <GIC_SPI 19 
IRQ_TYPE_LEVEL_HIGH>;
> +			clocks = <&osc24M>;
> +		};
> +
>  		wdt0: watchdog@...0ca0 {
>  			compatible = "allwinner,sun50i-a64-wdt",
>  				     "allwinner,sun6i-a31-wdt";
> diff --git a/arch/arm64/boot/dts/allwinner/sun50i-h6.dtsi
> b/arch/arm64/boot/dts/allwinner/sun50i-h6.dtsi index
> 62334054c710..9ba3b30e11fa 100644
> --- a/arch/arm64/boot/dts/allwinner/sun50i-h6.dtsi
> +++ b/arch/arm64/boot/dts/allwinner/sun50i-h6.dtsi
> @@ -332,6 +332,15 @@ cpu_speed_grade: cpu-speed-grade@1c {
>  			};
>  		};
> 
> +		timer@...9000 {
> +			compatible = "allwinner,sun50i-h6-timer",
> +				     "allwinner,sun8i-a23-timer";
> +			reg = <0x03009000 0xa0>;
> +			interrupts = <GIC_SPI 48 
IRQ_TYPE_LEVEL_HIGH>,
> +				     <GIC_SPI 49 
IRQ_TYPE_LEVEL_HIGH>;
> +			clocks = <&osc24M>;
> +		};
> +
>  		watchdog: watchdog@...90a0 {
>  			compatible = "allwinner,sun50i-h6-wdt",
>  				     "allwinner,sun6i-a31-wdt";
> diff --git a/arch/arm64/boot/dts/allwinner/sun50i-h616.dtsi
> b/arch/arm64/boot/dts/allwinner/sun50i-h616.dtsi index
> c277b53f94ea..ff55712ce96e 100644
> --- a/arch/arm64/boot/dts/allwinner/sun50i-h616.dtsi
> +++ b/arch/arm64/boot/dts/allwinner/sun50i-h616.dtsi

This file does not exist yet upstream.

Best regards,
Jernej

> @@ -128,6 +128,15 @@ ccu: clock@...1000 {
>  			#reset-cells = <1>;
>  		};
> 
> +		timer@...9000 {
> +			compatible = "allwinner,sun50i-h616-timer",
> +				     "allwinner,sun8i-a23-timer";
> +			reg = <0x03009000 0xa0>;
> +			interrupts = <GIC_SPI 48 
IRQ_TYPE_LEVEL_HIGH>,
> +				     <GIC_SPI 49 
IRQ_TYPE_LEVEL_HIGH>;
> +			clocks = <&osc24M>;
> +		};
> +
>  		watchdog: watchdog@...90a0 {
>  			compatible = "allwinner,sun50i-h616-wdt",
>  				     "allwinner,sun6i-a31-wdt";