From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
	id S932602AbbFIIb0 (ORCPT <rfc822;w@1wt.eu>);
	Tue, 9 Jun 2015 04:31:26 -0400
Received: from bombadil.infradead.org ([198.137.202.9]:43021 "EHLO
	bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
	with ESMTP id S1752512AbbFIIbR (ORCPT
	<rfc822;linux-kernel@vger.kernel.org>);
	Tue, 9 Jun 2015 04:31:17 -0400
Date: Tue, 9 Jun 2015 10:31:03 +0200
From: Peter Zijlstra <peterz@infradead.org>
To: Huang Rui <ray.huang@amd.com>
Cc: Borislav Petkov <bp@suse.de>, Andy Lutomirski <luto@amacapital.net>,
        Thomas Gleixner <tglx@linutronix.de>,
        "Rafael J. Wysocki" <rjw@rjwysocki.net>, Len Brown <lenb@kernel.org>,
        John Stultz <john.stultz@linaro.org>,
        =?iso-8859-1?Q?Fr=E9d=E9ric?= Weisbecker <fweisbec@gmail.com>,
        linux-kernel@vger.kernel.org, x86@kernel.org,
        Fengguang Wu <fengguang.wu@intel.com>, Aaron Lu <aaron.lu@intel.com>,
        Suravee Suthikulanit <suravee.suthikulpanit@amd.com>,
        Tony Li <tony.li@amd.com>, Ken Xue <ken.xue@amd.com>
Subject: Re: [PATCH v2 3/4] x86, mwaitt: introduce mwaix delay with a
 configurable timer
Message-ID: <20150609083103.GO3644@twins.programming.kicks-ass.net>
References: <1433819621-15093-1-git-send-email-ray.huang@amd.com>
 <1433819621-15093-4-git-send-email-ray.huang@amd.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <1433819621-15093-4-git-send-email-ray.huang@amd.com>
User-Agent: Mutt/1.5.21 (2012-12-30)
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On Tue, Jun 09, 2015 at 11:13:40AM +0800, Huang Rui wrote:
> MWAITX can enable a timer and a corresponding timer value specified in SW
> P0 clocks. The SW P0 frequency is the same with TSC. The timer provides an
> upper bound on how long the instruction waits before exiting.
> 
> The implementation of delay function in kernel can lerverage the timer of
> MWAITX. This patch provides a new method (delay_mwaitx) to measure delay
> time.

But does this actually default to mwaitx delay on capable hardware? If
you need to boot with that parameter it means nobody is ever going to
use this.