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From: "Li, Aubrey" <aubrey.li@linux.intel.com>
To: "Rafael J. Wysocki" <rjw@rjwysocki.net>, Alan Cox <alan@linux.intel.com>
Cc: Borislav Petkov <bp@alien8.de>,
	Arjan van de Ven <arjan@linux.intel.com>,
	Ingo Molnar <mingo@kernel.org>,
	"H. Peter Anvin" <hpa@linux.intel.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>,
	Len.Brown@intel.com, x86@kernel.org,
	LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] x86: Bypass legacy PIC and PIT on ACPI hardware reduced platform
Date: Thu, 05 Mar 2015 19:26:19 +0800	[thread overview]
Message-ID: <54F83D5B.6020109@linux.intel.com> (raw)
In-Reply-To: <8129220.9HmyqjfodP@vostro.rjw.lan>

On 2015/3/5 5:52, Rafael J. Wysocki wrote:
> On Wednesday, March 04, 2015 08:21:01 PM Alan Cox wrote:
>> On Wed, 2015-03-04 at 15:05 +0100, Borislav Petkov wrote:
>>> On Wed, Mar 04, 2015 at 03:16:07PM +0100, Rafael J. Wysocki wrote:
>>>> Sort of.  What we need is a "do not touch PIC/PIT" bit for the code that
>>>> tries to fall back to them in some cases (which may appear to work if
>>>> the hardware is physically there, but it may confuse the platform).
>>>
>>> Can "some cases" detection be nicely put into a x86_platform
>>> platform-specific method?
>>
>> In some cases they don't belong in x86, ACPI is also used for ARM64.
>>
>> However
>>
>> 	if ( has_8259_pic() )
>>
>> is trivally 0, 1 or some platform or acpi provided method.
> 
> And which is how that should have been implemented to start with IMO.
> 
> Besides, the "ACPI reduced hardware" case is kind of a red herring here,
> because it most likely is not the only case when we'll want has_8259_pic()
> to return 0 (quite likely, we'll want that on all BayTrail-based systems,
> for example).
> 
BayTrail-based systems has BayTrail-I, BayTrail-M, BayTrail-D,
BayTrail-T, BayTrail-T/CR. BayTrail-D is a desktop and BayTrail-M is a
mobile/laptop and 8259 exists on both systems and I don't think we want
to bypass it.

ACPI reduced hardware is the best case in my mind unless you want to
enumerate the platform one by one. can we make a global variable

u8 has_8259;

and initialize it by acpi reduced hardware flag? or a wrapper function?

Thanks,
-Aubrey

  reply	other threads:[~2015-03-05 11:26 UTC|newest]

Thread overview: 25+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-03-04  3:23 Li, Aubrey
2015-03-04  5:08 ` Ingo Molnar
2015-03-04  5:26   ` Li, Aubrey
2015-03-04  5:31     ` Ingo Molnar
2015-03-04  6:04       ` Li, Aubrey
2015-03-04  7:37         ` Ingo Molnar
2015-03-04  8:43           ` Arjan van de Ven
2015-03-04  9:50             ` Borislav Petkov
2015-03-04 14:16               ` Rafael J. Wysocki
2015-03-04 14:05                 ` Borislav Petkov
2015-03-04 14:38                   ` Rafael J. Wysocki
2015-03-04 20:21                   ` Alan Cox
2015-03-04 21:52                     ` Rafael J. Wysocki
2015-03-05 11:26                       ` Li, Aubrey [this message]
2015-03-05 16:05                       ` Alan Cox
2015-03-04 14:36               ` Arjan van de Ven
2015-03-04 20:11                 ` Ingo Molnar
2015-03-05 11:13                   ` Li, Aubrey
2015-03-05 11:36                     ` Ingo Molnar
2015-03-05 12:42                       ` Li, Aubrey
2015-03-05 16:06                         ` Alan Cox
2015-03-09 23:26                         ` Li, Aubrey
2015-03-10  8:06                           ` Ingo Molnar
2015-03-11  4:14                             ` Li, Aubrey
2015-03-04 20:18               ` Alan Cox

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