From mboxrd@z Thu Jan 1 00:00:00 1970 From: Lorenzo Pieralisi Subject: Re: [PATCH] ARM: kernel: DT cpu map validity check helper function Date: Thu, 10 Jan 2013 12:33:21 +0000 Message-ID: <20130110123321.GD4728@e102568-lin.cambridge.arm.com> References: <1357818507-8716-1-git-send-email-lorenzo.pieralisi@arm.com> <20130110121514.GD29952@linaro.org> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20130110121514.GD29952@linaro.org> Content-Disposition: inline List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: linux-arm-kernel-bounces@lists.infradead.org Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=m.gmane.org@lists.infradead.org To: Dave Martin Cc: Mark Rutland , Nicolas Pitre , Kukjin Kim , Russell King , Pawel Moll , Stephen Warren , Tony Lindgren , "devicetree-discuss@lists.ozlabs.org" , Magnus Damm , "rob.herring@calxeda.com" , Grant Likely , David Brown , "linux-arm-kernel@lists.infradead.org" , Hiroshi Doyu List-Id: devicetree@vger.kernel.org On Thu, Jan 10, 2013 at 12:15:14PM +0000, Dave Martin wrote: > On Thu, Jan 10, 2013 at 11:48:27AM +0000, Lorenzo Pieralisi wrote: > > Since the introduction of /cpu nodes bindings for ARM and the > > corresponding parse function arm_dt_init_cpu_maps(), the cpu_logical_map > > and the number of possible CPUs are set according to the DT /cpu > > nodes entries. Currently most of the existing ARM SMP platforms detect the > > number of cores through HW probing in their .smp_init_cpus functions and set > > the possible CPU mask accordingly. > > This method should be upgraded so that the CPU counting mechanism will be > > based on DT, keeping legacy HW probing mechanism as a fall back solution. > > > > In order to implement this fall back solution mechanism, the ARM DT code > > should provide a helper function to platforms to check if the cpu map > > has been properly initialized through DT. If the check fails the > > platform will resort to legacy HW based cores counting mechanism. > > > > This patch implements a trivial flag and a helper function that platform > > can call to check whether DT based cpu map initialization and cores count > > were completed successfully. > > > > Signed-off-by: Lorenzo Pieralisi > > --- > > arch/arm/include/asm/prom.h | 10 ++++++++++ > > arch/arm/kernel/devtree.c | 5 +++++ > > 2 files changed, 15 insertions(+) > > > > diff --git a/arch/arm/include/asm/prom.h b/arch/arm/include/asm/prom.h > > index a219227..487614a 100644 > > --- a/arch/arm/include/asm/prom.h > > +++ b/arch/arm/include/asm/prom.h > > @@ -18,6 +18,15 @@ > > extern struct machine_desc *setup_machine_fdt(unsigned int dt_phys); > > extern void arm_dt_memblock_reserve(void); > > extern void __init arm_dt_init_cpu_maps(void); > > +/* > > + * Return true if cpu map initialization has been > > + * carried out correctly from DT > > + */ > > +static inline bool __init arm_dt_cpu_map_valid(void) > > +{ > > + extern bool valid_dt_cpu_map; > > + return valid_dt_cpu_map; > > +} > > > > #else /* CONFIG_OF */ > > > > @@ -28,6 +37,7 @@ static inline struct machine_desc *setup_machine_fdt(unsigned int dt_phys) > > > > static inline void arm_dt_memblock_reserve(void) { } > > static inline void arm_dt_init_cpu_maps(void) { } > > +static inline bool __init arm_dt_cpu_map_valid(void) { return false; } > > > > #endif /* CONFIG_OF */ > > #endif /* ASMARM_PROM_H */ > > diff --git a/arch/arm/kernel/devtree.c b/arch/arm/kernel/devtree.c > > index 70f1bde..c82af3b 100644 > > --- a/arch/arm/kernel/devtree.c > > +++ b/arch/arm/kernel/devtree.c > > @@ -62,6 +62,10 @@ void __init arm_dt_memblock_reserve(void) > > memblock_reserve(base, size); > > } > > } > > +/* > > + * Export DT cpu map validity flag to platforms > > + */ > > +bool valid_dt_cpu_map __initdata; > > Is there any possibility of this being useful after boot? > Hopefully not, but maybe there's something I haven't considered. I do not think so, at least for the use cases I have envisaged at the moment, but it is certainly something I should consider. Thanks, Lorenzo