| Message ID | 1357921058-11322-1-git-send-email-lorenzo.pieralisi@arm.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Fri, Jan 11, 2013 at 04:17:38PM +0000, Lorenzo Pieralisi wrote: > This patch implements a helper function that platforms can call to check > whether DT based cpu map initialization and cores count were completed > successfully. Umm, are you sure this works? Two problems here: - the kernel boot marks the booting CPU (in our case, CPU0) as present, possible and online before arch code gets called. smp_init_cpus() will be called with the maps already initialized per that. - this really needs to be paired with a patch showing how you intend it to be used; merely adding the helper without any sign of it being used means it's just bloat which may not end up being used.
On Fri, Jan 11, 2013 at 04:30:57PM +0000, Russell King - ARM Linux wrote: > On Fri, Jan 11, 2013 at 04:17:38PM +0000, Lorenzo Pieralisi wrote: > > This patch implements a helper function that platforms can call to check > > whether DT based cpu map initialization and cores count were completed > > successfully. > > Umm, are you sure this works? Two problems here: > - the kernel boot marks the booting CPU (in our case, CPU0) as present, > possible and online before arch code gets called. smp_init_cpus() > will be called with the maps already initialized per that. Gah, my bad, you are definitely right. > - this really needs to be paired with a patch showing how you intend it > to be used; merely adding the helper without any sign of it being used > means it's just bloat which may not end up being used. Ok, that's a fair point, I will ask to get it merged with an implementation that relies on it, showing its usage. Thanks for the review, Lorenzo
diff --git a/arch/arm/include/asm/prom.h b/arch/arm/include/asm/prom.h index a219227..a913989 100644 --- a/arch/arm/include/asm/prom.h +++ b/arch/arm/include/asm/prom.h @@ -13,11 +13,21 @@ #define HAVE_ARCH_DEVTREE_FIXUPS +#include <linux/cpumask.h> + #ifdef CONFIG_OF 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) +{ + return !!(num_possible_cpus()); +} #else /* CONFIG_OF */ @@ -28,6 +38,7 @@ 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 */
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 helper function that platforms can call to check whether DT based cpu map initialization and cores count were completed successfully. Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com> --- arch/arm/include/asm/prom.h | 11 +++++++++++ 1 file changed, 11 insertions(+)