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Subject: Re: [PATCH 4/5] arm64: dts: allwinner: Add sun4i MMIO timer nodes
To:     =?UTF-8?Q?Jernej_=c5=a0krabec?= <jernej.skrabec@siol.net>,
        Daniel Lezcano <daniel.lezcano@linaro.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Rob Herring <robh+dt@kernel.org>,
        Maxime Ripard <mripard@kernel.org>,
        Chen-Yu Tsai <wens@csie.org>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Will Deacon <will@kernel.org>
Cc:     devicetree@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
        linux-kernel@vger.kernel.org
References: <20210315043250.45095-1-samuel@sholland.org>
 <20210315043250.45095-5-samuel@sholland.org>
 <1897259.uecf0MpyRy@jernej-laptop>
From:   Samuel Holland <samuel@sholland.org>
Message-ID: <43b4d9e5-55c8-c844-069f-c8f8290c20e2@sholland.org>
Date:   Mon, 15 Mar 2021 23:35:24 -0500
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On 3/15/21 1:32 PM, Jernej Škrabec wrote:
> 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@sholland.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@1c20c00 {
>> +			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@1c20ca0 {
>>  			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@3009000 {
>> +			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@30090a0 {
>>  			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.

Right. I will remove this section for v2.

Cheers,
Samuel

> Best regards,
> Jernej
> 
>> @@ -128,6 +128,15 @@ ccu: clock@3001000 {
>>  			#reset-cells = <1>;
>>  		};
>>
>> +		timer@3009000 {
>> +			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@30090a0 {
>>  			compatible = "allwinner,sun50i-h616-wdt",
>>  				     "allwinner,sun6i-a31-wdt";
> 
> 
> 
>