linux-kernel - Re: [PATCH v2] x86: hpet: Don't default CONFIG_HPET_TIMER to be y for X86

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Message-ID: <20140328071716.GC30107@gmail.com>
Date:	Fri, 28 Mar 2014 08:17:16 +0100
From:	Ingo Molnar <mingo@...nel.org>
To:	Feng Tang <feng.tang@...el.com>
Cc:	tglx@...utronix.de, mingo@...e.hu, hpa@...or.com,
	linux-kernel@...r.kernel.org, John Stultz <john.stultz@...aro.org>,
	Clemens Ladisch <clemens@...isch.de>,
	Andy Lutomirski <luto@...capital.net>
Subject: Re: [PATCH v2] x86: hpet: Don't default CONFIG_HPET_TIMER to be y
 for X86_64


* Feng Tang <feng.tang@...el.com> wrote:

> On many new phone/tablet platforms like Baytrail/Merrifield etc, the 
> HPET are either defeatured or has some problem to be used as a 
> reliable timer. As these platforms also have X86_64, we should not 
> make HPET_TIMER default y for all X86_64.

NAK!

If the HPET is unreliable on a specific platform then any of the 
following solutions would address the problem (in order of 
preference):

 - the hardware should not expose it. Why waste silicon on something 
   that does not work?

 - or the firmware should not expose it. Why expose something that 
   does not work?

 - or the kernel should have a quirk to reliably disable it. Why 
   should we crash or misbehave if a driver is built into the
   kernel?

tweaking a default is _NOT_ a solution for an unreliable hpet.

Thanks,

	Ingo
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