linux-kernel - Re: [PATCH] arm64: Kconfig: Add SYS_SUPPORTS_APM

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Date:   Wed, 16 Dec 2020 15:58:20 +0000
From:   Catalin Marinas <catalin.marinas@....com>
To:     Lecopzer Chen <lecopzer.chen@...iatek.com>
Cc:     mark.rutland@....com, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, linux-mediatek@...ts.infradead.org,
        matthias.bgg@...il.com, will@...nel.org, yj.chiang@...iatek.com
Subject: Re: [PATCH] arm64: Kconfig: Add SYS_SUPPORTS_APM_EMULATION

On Wed, Nov 25, 2020 at 07:41:30PM +0800, Lecopzer Chen wrote:
> >> In order to select CONFIG_APM_EMULATION, make SYS_SUPPORTS_APM_EMULATION
> >> default is y if ACPI isn't configured.
> >
> >I'm a bit confused why this should be enabled for !ACPI. Which DT
> >platforms need this, and how do they use it? Why should this only be
> >enabled for kernels without ACPI support, and not for kernels that
> >support both ACPI and DT?
> 
> In our internal patch has no !ACPI here,
> the reason I add here is that in kernel document[1] it mention:
> > No, sorry, you cannot have both ACPI and APM enabled and running at once.
> Thus, I try to limit the scope for who don't use the ACPI because I'm not sure
> they could exist at the same time or not.
> 
> But I think it should be fine without !ACPI if APM and APCI
> config won't conflict with each other.
> 
> So if it's better to remove !ACPI I'll send v2 for this.
> 
> BTW, The platform is for our internal kernel drivers, they utilize APM interface,
> /dev/apm_bios to do their works in arm64.

Sorry, I don't think the APM interface makes sense on an arm64 kernel
(and it's also used by an out of tree driver).

-- 
Catalin