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

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Date:   Thu, 17 Dec 2020 00:41:47 +0800
From:   Lecopzer Chen <lecopzer.chen@...iatek.com>
To:     <catalin.marinas@....com>
CC:     <lecopzer.chen@...iatek.com>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>,
        <linux-mediatek@...ts.infradead.org>, <mark.rutland@....com>,
        <matthias.bgg@...il.com>, <will@...nel.org>,
        <yj.chiang@...iatek.com>
Subject: Re: [PATCH] arm64: Kconfig: Add SYS_SUPPORTS_APM_EMULATION

Hi Catalin,

Thanks for your reply.

so there is two points
1. out-of-tree function can't be approved
    I totally agree with this :) so we may have a driver upstream in the future.
2. APM not make sense on arm64
Could you please let me konw the reason why APM on ARM64 doesn't make sense?


thanks!
BRs,
Lecopzer


> 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).