Re: [PATCH] LoongArch: Give chance to build under !CONFIG_SMP

[Tiezhu Yang]

Hi Bibo,

On 3/26/24 20:58, maobibo wrote:
> On 2024/3/26 下午2:21, Tiezhu Yang wrote:
> > In the current code, SMP is selected in Kconfig for LoongArch, the users
> > can not unset it, this is reasonable for a multiprocessor machine. But as
> > the help info of config SMP said, if you have a system with only one CPU,
> > say N. On a uniprocessor machine, the kernel will run faster if you say N
> > here.
> >
> > The Loongson-2K0500 is a single-core CPU for applications like industrial
> > control, printing terminals, and BMC (Baseboard Management Controller),
> > there are many development boards, products and solutions on the market,
> > so it is better and necessary to give a chance to build under !CONFIG_SMP
> > for a uniprocessor machine.

..

> > +++ b/arch/loongarch/include/asm/smp.h
> > @@ -6,6 +6,7 @@
> >   #ifndef __ASM_SMP_H
> >   #define __ASM_SMP_H
> > +#ifdef CONFIG_SMP
> >   #include <linux/atomic.h>
> >   #include <linux/bitops.h>
> >   #include <linux/linkage.h>
> > @@ -101,4 +102,8 @@ static inline void __cpu_die(unsigned int cpu)
> >   }
> >   #endif
> > +#else /* !CONFIG_SMP */
> > +#define cpu_logical_map(cpu)    0
> It is unsafe here though physical cpuid of BSP is 0 always.
> It is better to use __cpu_logical_map[cpu] or read_csr_cpuid()
>
> > +#endif

..

> > +++ b/arch/loongarch/power/suspend.c
> > @@ -44,7 +44,9 @@ void loongarch_common_resume(void)
> >   {
> >       sync_counter();
> >       local_flush_tlb_all();
> > +#ifdef CONFIG_HAVE_SETUP_PER_CPU_AREA
> >       csr_write64(per_cpu_offset(0), PERCPU_BASE_KS);
> > +#endif
> It is another issue, CONFIG_HAVE_SETUP_PER_CPU_AREA should not depend on 
> NUMA. PERCPU_BASE_KS should be set even for UP.

Thanks for your review and suggestions.

Let me wait for some days, if no more comments, I will address in v3 
since the v2 has been sent.

Thanks,
Tiezhu