On Thu, Jan 10, 2013 at 02:03:50PM +0000, Hiroshi Doyu wrote:
> Lorenzo Pieralisi <lorenzo.pieralisi@xxxxxxx> wrote @ Thu, 10 Jan 2013 14:47:23 +0100:
[...]
> > > +static int __init smp_detect_ncores(void)
> > > +{
> > > + unsigned int ncores, mpidr;
> > > + u32 l2ctlr;
> > > + phys_addr_t pa;
> > > +
> > > + mpidr = read_cpuid_mpidr();
> > > + switch (mpidr) {
> > > + case ARM_CPU_PART_CORTEX_A15:
> > > + asm("mrc p15, 1, %0, c9, c0, 2\n" : "=r" (l2ctlr));
> > > + ncores = ((l2ctlr >> 24) & 3) + 1;
> > > + break;
> >
> > I do not want to see the case above merged. We keep the existing legacy
> > methods there for legacy reasons and as a fall-back mechanism but I am not
> > keen on adding new HW probing code to detect the number of cores.
> >
> > From A15/A7 onwards DT-only cpu map initialization is the way to go.
>
> Ok, then, smp_detect_ncores(void) could be...
>
> static int __init smp_detect_ncores(void)
> {
> unsigned int ncores, mpidr;
> phys_addr_t pa;
>
> mpidr = read_cpuid_mpidr();
Careful, MPIDR is not at all what you want. MIDR is.
> switch (mpidr) {
> case ARM_CPU_PART_CORTEX_A9:
> /* Get SCU physical base */
> asm("mrc p15, 4, %0, c15, c0, 0" : "=r" (pa));
> scu_base = IO_ADDRESS(pa);
> ncores = scu_get_core_count(scu_base);
> break;
> case ARM_CPU_PART_CORTEX_A15:
Remove the ARM_CPU_PART_CORTEX_A15 case, I do not see how it helps.
And be careful with the case matching, if I am not mistaken read_cpuid_id()
(which is the function you have to use) will return the full MIDR, you need
to mask the return value.
> default:
> pr_warn("Unsupported MPIDR %x\n", mpidr);
> ncores = 1;
> break;
This is reasonable.
Lorenzo
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