linux-kernel - Re: [PATCH v7 04/17] ARM64 / ACPI: Introduce early_param for "acpi" and pass acpi=force to enable ACPI

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Date:	Mon, 19 Jan 2015 11:55:32 +0000
From:	Ard Biesheuvel <ard.biesheuvel@...aro.org>
To:	Catalin Marinas <catalin.marinas@....com>
Cc:	"hanjun.guo@...aro.org" <hanjun.guo@...aro.org>,
	Mark Rutland <Mark.Rutland@....com>,
	"linaro-acpi@...ts.linaro.org" <linaro-acpi@...ts.linaro.org>,
	Will Deacon <Will.Deacon@....com>,
	"wangyijing@...wei.com" <wangyijing@...wei.com>,
	Rob Herring <robh@...nel.org>,
	Lorenzo Pieralisi <Lorenzo.Pieralisi@....com>,
	Al Stone <al.stone@...aro.org>,
	Timur Tabi <timur@...eaurora.org>,
	"linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>,
	"grant.likely@...aro.org" <grant.likely@...aro.org>,
	Charles Garcia-Tobin <Charles.Garcia-Tobin@....com>,
	"phoenix.liyi@...wei.com" <phoenix.liyi@...wei.com>,
	Robert Richter <rric@...nel.org>,
	Jason Cooper <jason@...edaemon.net>,
	Arnd Bergmann <arnd@...db.de>,
	Marc Zyngier <Marc.Zyngier@....com>,
	"jcm@...hat.com" <jcm@...hat.com>, Mark Brown <broonie@...nel.org>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"graeme.gregory@...aro.org" <graeme.gregory@...aro.org>,
	Randy Dunlap <rdunlap@...radead.org>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"suravee.suthikulpanit@....com" <suravee.suthikulpanit@....com>,
	Sudeep Holla <Sudeep.Holla@....com>,
	Olof Johansson <olof@...om.net>
Subject: Re: [PATCH v7 04/17] ARM64 / ACPI: Introduce early_param for "acpi"
 and pass acpi=force to enable ACPI

On 19 January 2015 at 11:42, Catalin Marinas <catalin.marinas@....com> wrote:
> On Wed, Jan 14, 2015 at 03:04:52PM +0000, Hanjun Guo wrote:
>> From: Al Stone <al.stone@...aro.org>
>>
>> Introduce one early parameters "off" and "force" for "acpi", acpi=off
>> will be the default behavior for ARM64, so introduce acpi=force to
>> enable ACPI on ARM64.
>>
>> Disable ACPI before early parameters parsed, and enable it to pass
>> "acpi=force" if people want use ACPI on ARM64. This ensures DT be
>> the prefer one if ACPI table and DT both are provided at this moment.
> [...]
>> --- a/arch/arm64/kernel/setup.c
>> +++ b/arch/arm64/kernel/setup.c
>> @@ -62,6 +62,7 @@
>>  #include <asm/memblock.h>
>>  #include <asm/psci.h>
>>  #include <asm/efi.h>
>> +#include <asm/acpi.h>
>>
>>  unsigned int processor_id;
>>  EXPORT_SYMBOL(processor_id);
>> @@ -388,6 +389,8 @@ void __init setup_arch(char **cmdline_p)
>>       early_fixmap_init();
>>       early_ioremap_init();
>>
>> +     disable_acpi();
>> +
>>       parse_early_param();
>>
>>       /*
>
> Did we get to any conclusion here? DT being the preferred one is fine
> when both DT and ACPI are present but do we still want the kernel to
> ignore ACPI altogether if DT is not present? It's a bit harder to detect
> the presence of DT at this point since the EFI_STUB added one already. I
> guess we could move the "acpi=force" argument passing to EFI_STUB if no
> DT is present at boot.
>

Since the EFI stub populates the /chosen node in DT, I would prefer
for it to add a property there to indicate whether it created the DT
from scratch rather than adding ACPI specific stuff in there (even if
it is just a string to concatenate)

-- 
Ard.
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