linux-kernel - Re: [PATCH v3 2/2] ARM: dts: sun8i-r40: Add "cpu-supply" node for sun8i-r40 based board

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Date:   Fri, 13 May 2022 15:48:50 +0800
From:   qianfan <qianfanguijin@....com>
To:     Maxime Ripard <maxime@...no.tech>
Cc:     linux-sunxi@...ts.linux.dev, Rob Herring <robh+dt@...nel.org>,
        Chen-Yu Tsai <wens@...e.org>,
        Jernej Skrabec <jernej.skrabec@...il.com>,
        "Rafael J . Wysocki" <rafael@...nel.org>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org
Subject: Re: [PATCH v3 2/2] ARM: dts: sun8i-r40: Add "cpu-supply" node for
 sun8i-r40 based board



在 2022/5/13 15:38, Maxime Ripard 写道:
> Hi,
>
> On Thu, May 12, 2022 at 03:18:58PM +0800, qianfanguijin@....com wrote:
>> From: qianfan Zhao <qianfanguijin@....com>
>>
>> sun8i-r40 actived cpufreq feature now, let's add "cpu-supply" node on
>> board.
>>
>> Signed-off-by: qianfan Zhao <qianfanguijin@....com>
>> ---
>>   arch/arm/boot/dts/sun8i-r40-bananapi-m2-ultra.dts | 4 ++++
>>   arch/arm/boot/dts/sun8i-r40-feta40i.dtsi          | 4 ++++
>>   arch/arm/boot/dts/sun8i-t3-cqa3t-bv3.dts          | 4 ++++
>>   arch/arm/boot/dts/sun8i-v40-bananapi-m2-berry.dts | 4 ++++
>>   4 files changed, 16 insertions(+)
>>
>> diff --git a/arch/arm/boot/dts/sun8i-r40-bananapi-m2-ultra.dts b/arch/arm/boot/dts/sun8i-r40-bananapi-m2-ultra.dts
>> index a6a1087a0c9b..4f30018ec4a2 100644
>> --- a/arch/arm/boot/dts/sun8i-r40-bananapi-m2-ultra.dts
>> +++ b/arch/arm/boot/dts/sun8i-r40-bananapi-m2-ultra.dts
>> @@ -113,6 +113,10 @@ &ahci {
>>   	status = "okay";
>>   };
>>   
>> +&cpu0 {
>> +	cpu-supply = <&reg_dcdc2>;
>> +};
>> +
> This will break bisection on those boards. Indeed, you added the OPPs on
> the first patch, and if you only apply that patch, the boards in the
> second patch will be missing their CPU regulator. The kernel will then
> ramp up the frequency to the highest OPP, but will not change the
> voltage, resulting in a crash.
This is a good point and I will merge those two patch.
>
> There's a similar issue for all the boards that don't have a regulator
> in the first place.
>
> The way we worked around this for the other SoCs is to have a DTSI with
> the OPPs with a frequency higher than what U-Boot boots with (1008MHz?),
> and only include that DTSI on boards that have a CPU regulator hooked in.
Is this really necessary? It seems like every board based on sun8i-r40
have a cpu regulator.
>
> Maxime