Re: [PATCH v3 3/4] LoongArch: Save and restore PERCPU_BASE_KS for ACPI S3 state

[Tiezhu Yang]

On 04/12/2024 12:18 PM, Huacai Chen wrote:
> Hi, Tiezhu,
>
> On Thu, Apr 11, 2024 at 9:05 AM Tiezhu Yang <yangtiezhu@xxxxxxxxxxx> wrote:
> > Currently, per_cpu_offset(x) is defined as __per_cpu_offset[x])
> > only under CONFIG_SMP in include/asm-generic/percpu.h, that is
> > to say, the implementation of loongarch_common_resume() which
> > calls per_cpu_offset(0) is not suitable for the case of non-SMP,
> > so do not write per_cpu_offset(0) to PERCPU_BASE_KS when resume,
> > just save the value of PERCPU_BASE_KS when suspend and restore
> > it when resume to make it work well for both SMP and non-SMP.
> For non-SMP you need PERCPU_BASE_KS to do what?

The initial aim is to avoid build error under !CONFIG_SMP
and it works well on both !CONFIG_SMP and CONFIG_SMP, the
changes are similar with the code in hibernate.c.

An alternative way is to do the following simple change,
but it seems a little ugly due to the ifdef, let me know
what is your preference.

diff --git a/arch/loongarch/power/suspend.c b/arch/loongarch/power/suspend.c
index 166d9e06a64b..35191afefcda 100644
--- a/arch/loongarch/power/suspend.c
+++ b/arch/loongarch/power/suspend.c
@@ -44,7 +44,9 @@ void loongarch_common_resume(void)
 {
        sync_counter();
        local_flush_tlb_all();
+#ifdef
        csr_write64(per_cpu_offset(0), PERCPU_BASE_KS);
+#endif
        csr_write64(eentry, LOONGARCH_CSR_EENTRY);
        csr_write64(eentry, LOONGARCH_CSR_MERRENTRY);
        csr_write64(tlbrentry, LOONGARCH_CSR_TLBRENTRY);

Thanks,
Tiezhu