Marc Zyngier <marc.zyngier@xxxxxxx> wrote @ Thu, 20 Dec 2012 12:17:08 +0100: > On 20/12/12 09:44, Hiroshi Doyu wrote: > > The method to detect the number of CPU cores on Cortex-A9 MPCore and > > Cortex-A15 MPCore is different. On Cortex-A9 MPCore we can get this > > information from the Snoop Control Unit(SCU). On Cortex-A15 MPCore we > > have to read it from the system coprocessor(CP15), because the SCU on > > Cortex-A15 MPCore does not have software readable registers. This > > patch selects the correct method at runtime based on the CPU ID. > > > > Signed-off-by: Hiroshi Doyu <hdoyu@xxxxxxxxxx> > > --- > > arch/arm/mach-tegra/platsmp.c | 31 ++++++++++++++++++++++++++++--- > > 1 file changed, 28 insertions(+), 3 deletions(-) > > > > diff --git a/arch/arm/mach-tegra/platsmp.c b/arch/arm/mach-tegra/platsmp.c > > index 1b926df..68e76ef 100644 > > --- a/arch/arm/mach-tegra/platsmp.c > > +++ b/arch/arm/mach-tegra/platsmp.c > > @@ -23,6 +23,7 @@ > > #include <asm/hardware/gic.h> > > #include <asm/mach-types.h> > > #include <asm/smp_scu.h> > > +#include <asm/cputype.h> > > > > #include <mach/powergate.h> > > > > @@ -34,9 +35,13 @@ > > #include "common.h" > > #include "iomap.h" > > > > +#define CPU_MASK 0xff0ffff0 > > +#define CPU_CORTEX_A9 0x410fc090 > > +#define CPU_CORTEX_A15 0x410fc0f0 > > + > > extern void tegra_secondary_startup(void); > > > > -static void __iomem *scu_base = IO_ADDRESS(TEGRA_ARM_PERIF_BASE); > > +static void __iomem *scu_base; > > > > #define EVP_CPU_RESET_VECTOR \ > > (IO_ADDRESS(TEGRA_EXCEPTION_VECTORS_BASE) + 0x100) > > @@ -149,7 +154,26 @@ done: > > */ > > static void __init tegra_smp_init_cpus(void) > > { > > - unsigned int i, ncores = scu_get_core_count(scu_base); > > + unsigned int i, cpu_id, ncores; > > + u32 l2ctlr; > > + phys_addr_t pa; > > + > > + cpu_id = read_cpuid(CPUID_ID) & CPU_MASK; > > + switch (cpu_id) { > > + case CPU_CORTEX_A15: > > + asm("mrc p15, 1, %0, c9, c0, 2\n" : "=r" (l2ctlr)); > > + ncores = ((l2ctlr >> 24) & 3) + 1; > > Please, do not do that. It doesn't scale to multiple clusters. Instead, > you can now rely on arm_dt_init_cpu_maps() to do the right thing as long > as your device tree exposes all the cpu nodes. Ok, this could be the answer why DT for cpu is necessary even when it's got from CP15? http://lists.infradead.org/pipermail/linux-arm-kernel/2012-December/137989.html -- To unsubscribe from this list: send the line "unsubscribe linux-doc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html