From mboxrd@z Thu Jan 1 00:00:00 1970 From: catalin.marinas@arm.com (Catalin Marinas) Date: Thu, 02 Dec 2010 16:28:40 +0000 Subject: [PATCH 1/8] ARM: SCU: Add common routines for secondary CPU bootup In-Reply-To: <20101202152428.GD10461@n2100.arm.linux.org.uk> References: <20101130171626.GA6165@oksana.dev.rtsoft.ru> <20101130171658.GA24034@oksana.dev.rtsoft.ru> <20101130233204.GB14383@n2100.arm.linux.org.uk> <20101201002527.GC14383@n2100.arm.linux.org.uk> <20101202152428.GD10461@n2100.arm.linux.org.uk> Message-ID: <1291307320.11271.51.camel@e102109-lin.cambridge.arm.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Thu, 2010-12-02 at 15:24 +0000, Russell King - ARM Linux wrote: > On Thu, Dec 02, 2010 at 03:19:05PM +0000, Catalin Marinas wrote: > > On 1 December 2010 00:25, Russell King - ARM Linux > > wrote: > > > On Tue, Nov 30, 2010 at 11:32:04PM +0000, Russell King - ARM Linux wrote: > > >> Note that I'll go with factoring this out into arch/arm/kernel/smp_scu.c > > >> for the time being, but I'm not convinced about the other parts yet. > > > > > > IOW, something like the attached. I've gone a little further and removed > > > the now unnecessary scu_enable() and scu_get_core_count() global functions, > > > making scu_enable() static, and eliminating scu_get_core_count() entirely. > > > > There is some benefit in leaving get_core_count() in the platform > > code. For example, the SCU on Cortex-A15 doesn't expose the core count > > register and we have to get it from somewhere else (for now from some > > L2 cache controller register but in the future it may be hardcoded, > > passed via FDT or simply trying to boot maxcpus). > > I notice that there's no way to tell what revision of SCU is implemented > on _any_ mpcore platform. C-A15 doesn't have any SCU registers exposed (and it's enabled by default). > In light of that, I think there's no point what so ever trying to > consolidate this code - even the control register bits vary in > unpredictable ways between different MPcore implementations. The SCU is part of the core TRM, so I don't expect it to be the same across various MP cores (and A15 is an example). You may want to consolidate functions like scu_prepare_cpus (maybe call it smp_prepare_cpus) and something that calls set_cpu_possible() but with platform callbacks for getting the number of calls and initialising the SMP (SCU for most platforms). Whether this is worth, I don't know. -- Catalin