Re: [PATCH] arm64: Kconfig: Add SYS_SUPPORTS_APM_EMULATION

From: Lecopzer Chen <lecopzer.chen@mediatek.com>
To: <mark.rutland@arm.com>
Cc: <catalin.marinas@arm.com>, <lecopzer.chen@mediatek.com>,
	<linux-arm-kernel@lists.infradead.org>,
	<linux-kernel@vger.kernel.org>,
	<linux-mediatek@lists.infradead.org>, <matthias.bgg@gmail.com>,
	<will@kernel.org>, <yj.chiang@mediatek.com>
Subject: Re: [PATCH] arm64: Kconfig: Add SYS_SUPPORTS_APM_EMULATION
Date: Wed, 25 Nov 2020 19:41:30 +0800	[thread overview]
Message-ID: <20201125114130.507-1-lecopzer.chen@mediatek.com> (raw)
In-Reply-To: <20201125103637.GC70906@C02TD0UTHF1T.local>

>> From: "Lecopzer Chen" <lecopzer.chen@mediatek.com>
>> 
>> Although most of modern devices use ACPI, there still has combination
>> of APM + ARM64.
>> 
>> 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?
>
>Thanks,
>Mark.

Hi Mark,

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.

[1] APM or ACPI?:
https://www.kernel.org/doc/html/latest/power/apm-acpi.html

Thanks,
Lecopzer

>> 
>> Signed-off-by: Lecopzer Chen <lecopzer.chen@mediatek.com>
>> Suggested-by: YJ Chiang <yj.chiang@mediatek.com>
>> ---
>>  arch/arm64/Kconfig | 3 +++
>>  1 file changed, 3 insertions(+)
>> 
>> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
>> index 1515f6f153a0..5e9e3694015a 100644
>> --- a/arch/arm64/Kconfig
>> +++ b/arch/arm64/Kconfig
>> @@ -260,6 +260,9 @@ config NO_IOPORT_MAP
>>  config STACKTRACE_SUPPORT
>>  	def_bool y
>>  
>> +config SYS_SUPPORTS_APM_EMULATION
>> +	def_bool y if !ACPI
>> +
>>  config ILLEGAL_POINTER_VALUE
>>  	hex
>>  	default 0xdead000000000000
>> -- 
>> 2.18.0
>> 