From mboxrd@z Thu Jan 1 00:00:00 1970 From: dirk.behme@de.bosch.com (Dirk Behme) Date: Thu, 14 Feb 2013 15:47:50 +0100 Subject: i.MX6 Solo: maxcpus=1 vs. nosmp: Warning from smp_twd.c? In-Reply-To: References: <511CF063.3010200@de.bosch.com> Message-ID: <511CF916.2060705@de.bosch.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On 14.02.2013 15:40, Fabio Estevam wrote: > Hi Dirk, > > On Thu, Feb 14, 2013 at 12:10 PM, Dirk Behme wrote: >> Hi, >> >> working on a i.MX6 Solo SoC (one Cortex A9 core) we are usually booting with >> maxcpus=1 a kernel built with CONFIG_NR_CPUS=4. This is done to be able to >> boot the same kernel on the Solo and Quad version of that SoC. >> >> Now, we tried to switch from 'maxcpus=1' to 'nosmp'. With 'nosmp' we get the >> warning [1] in the boot messages. This isn't there with 'maxcpus=1'. > > maxcpus=1 and nosmp are not equivalent as per the comment from kernel/smp.c: > > /* > * Setup routine for controlling SMP activation > * > * Command-line option of "nosmp" or "maxcpus=0" will disable SMP > * activation entirely (the MPS table probe still happens, though). > * > * Command-line option of "maxcpus=", where is an integer > * greater than 0, limits the maximum number of CPUs activated in > * SMP mode to . > */ Yes, understood that both options are not equal. But should both options work on a single ARM Cortex A9 SoC without a warning? Or should one of the both options be preferred on a single ARM Cortex A9 SoC? Thanks Dirk