From mboxrd@z Thu Jan 1 00:00:00 1970 From: Paul Mundt Subject: Re: [PATCH] arm: platsmp: Allow secondary cpu hotplug with maxcpus=1 Date: Thu, 30 Jun 2011 14:38:52 +0900 Message-ID: <20110630053851.GC22023@linux-sh.org> References: <1309372300-28911-1-git-send-email-sboyd@codeaurora.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <1309372300-28911-1-git-send-email-sboyd@codeaurora.org> Sender: linux-sh-owner@vger.kernel.org To: Stephen Boyd Cc: Russell King , linux-kernel@vger.kernel.org, linux-arm-msm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-samsung-soc@vger.kernel.org, linux-omap@vger.kernel.org, linux-sh@vger.kernel.org, linux-tegra@vger.kernel.org, Kukjin Kim , David Brown , Tony Lindgren , Srinidhi Kasagar , Linus Walleij List-Id: linux-tegra@vger.kernel.org On Wed, Jun 29, 2011 at 11:31:39AM -0700, Stephen Boyd wrote: > If an ARM system has multiple cpus in the same socket and the > kernel is booted with maxcpus=1, secondary cpus are possible but > not present due to how platform_smp_prepare_cpus() is called. > Fix this by always calling platform_smp_prepare_cpus() as long as > max_cpus is non-zero (0 means no SMP) to allow platform code to > decide if any non-boot cpus are present in the system. Since > all current platform code doesn't support physical hotplug we > have a situation where possible == present and thus we can > simply copy the possible map to the present map. > > With this patch it's possible to boot an ARM system with > maxcpus=1 on the command line and then hotplug in secondary cpus > via sysfs. This is more in line with how x86 works with maxcpus=1 > on the command line. > > Signed-off-by: Stephen Boyd Acked-by: Paul Mundt