From mboxrd@z Thu Jan 1 00:00:00 1970 From: tony@atomide.com (Tony Lindgren) Date: Wed, 31 May 2017 07:39:15 -0700 Subject: [CFT] Always enable SMP mode on MP capable CPUs In-Reply-To: <20170527132237.GX23750@n2100.armlinux.org.uk> References: <20170519171526.GW22219@n2100.armlinux.org.uk> <20170524153847.GY10472@atomide.com> <20170525144800.GV23750@n2100.armlinux.org.uk> <20170525151103.GC10472@atomide.com> <20170525180540.GW23750@n2100.armlinux.org.uk> <20170525221332.GE10472@atomide.com> <20170526112210.GA3354@afzalpc> <20170527132237.GX23750@n2100.armlinux.org.uk> Message-ID: <20170531143914.GD3730@atomide.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org * Russell King - ARM Linux [170527 06:26]: > On Fri, May 26, 2017 at 04:52:10PM +0530, afzal mohammed wrote: > > Hi, > > > > On Thu, May 25, 2017 at 03:13:33PM -0700, Tony Lindgren wrote: > > > > > OK so got my am437x-idk back > > > > > > And as suspected it won't boot with these changes. > > > > Tested here too with your additional changes included & seeing same > > behavior here as well on AM437x. > > > > As an aside, when Russell posted this patch a week back itself was > > suspecting this. i had a certain view on AM437x w.r.t SMP issue back > > while officially working on it & since now not officially involved > > with the issue at hand, i was uncomfortable dealing with this. But as > > Russell's patch was not noticed by others w.r.t AM437x, upon being > > able to confirm it yesterday, i at least wanted to bring it to notice > > & runaway from the scene. > > Right, so I think the summary is: the kernel can't set the SMP bit > correctly - it doesn't have the information at this point in time > to know definitively whether the bit needs to be set or not. > > So, those who are suffering issues with their SMP cores in uniprocessor > systems need to ensure that their boot loader correctly configures the > CPU cores. Russell, current Linux next still has commit e7cf836e9757 ("ARM: always enable SMP mode on SMP cores"). You're planning to drop it, right? It causes a regression on am437x to not boot as we can't set the SMP bit on it. Regards, Tony