Re: [PATCH 2/5] LoongArch: Probe more CPU features from CPUCFG

[Huacai Chen]

Hi, Jiaxun,

On Sat, Sep 7, 2024 at 6:17 PM Jiaxun Yang <jiaxun.yang@xxxxxxxxxxx> wrote:
>
> Probe ISA level, TLB, IOCSR information from CPUCFG to
> improve kernel resilience to different core implementations.
>
> Signed-off-by: Jiaxun Yang <jiaxun.yang@xxxxxxxxxxx>
> ---
>  arch/loongarch/include/asm/cpu.h  |  2 +-
>  arch/loongarch/kernel/cpu-probe.c | 47 ++++++++++++++++++++++++++-------------
>  2 files changed, 32 insertions(+), 17 deletions(-)
>
> diff --git a/arch/loongarch/include/asm/cpu.h b/arch/loongarch/include/asm/cpu.h
> index 7c44f4ede3a2..31a2de821236 100644
> --- a/arch/loongarch/include/asm/cpu.h
> +++ b/arch/loongarch/include/asm/cpu.h
> @@ -86,7 +86,7 @@ enum cpu_type_enum {
>  #define CPU_FEATURE_LBT_ARM            11      /* CPU has ARM Binary Translation */
>  #define CPU_FEATURE_LBT_MIPS           12      /* CPU has MIPS Binary Translation */
>  #define CPU_FEATURE_TLB                        13      /* CPU has TLB */
> -#define CPU_FEATURE_CSR                        14      /* CPU has CSR */
> +#define CPU_FEATURE_IOCSR              14      /* CPU has IOCSR */
>  #define CPU_FEATURE_WATCH              15      /* CPU has watchpoint registers */
>  #define CPU_FEATURE_VINT               16      /* CPU has vectored interrupts */
>  #define CPU_FEATURE_CSRIPI             17      /* CPU has CSR-IPI */
> diff --git a/arch/loongarch/kernel/cpu-probe.c b/arch/loongarch/kernel/cpu-probe.c
> index 4446616d497c..6a82ceb6e321 100644
> --- a/arch/loongarch/kernel/cpu-probe.c
> +++ b/arch/loongarch/kernel/cpu-probe.c
> @@ -91,12 +91,23 @@ static void cpu_probe_common(struct cpuinfo_loongarch *c)
>         unsigned int config;
>         unsigned long asid_mask;
>
> -       c->options = LOONGARCH_CPU_CPUCFG | LOONGARCH_CPU_IOCSR |
> -                    LOONGARCH_CPU_TLB | LOONGARCH_CPU_VINT | LOONGARCH_CPU_WATCH;
> +       c->options = LOONGARCH_CPU_CPUCFG | LOONGARCH_CPU_VINT |
> +                    LOONGARCH_CPU_WATCH;
>
>         elf_hwcap = HWCAP_LOONGARCH_CPUCFG;
>
>         config = read_cpucfg(LOONGARCH_CPUCFG1);
> +
> +       if (config & CPUCFG1_ISGR64)
> +               set_isa(c, LOONGARCH_CPU_ISA_LA64);
> +       else if (config & CPUCFG1_ISGR32)
> +               set_isa(c, LOONGARCH_CPU_ISA_LA32S);
> +       else
> +               set_isa(c, LOONGARCH_CPU_ISA_LA32R);
Switch-case is better than if-else here.

> +       if (config & CPUCFG1_PAGING)
> +               c->options |= LOONGARCH_CPU_TLB;
> +       if (config & CPUCFG1_IOCSR)
> +               c->options |= LOONGARCH_CPU_IOCSR;
>         if (config & CPUCFG1_UAL) {
>                 c->options |= LOONGARCH_CPU_UAL;
>                 elf_hwcap |= HWCAP_LOONGARCH_UAL;
> @@ -222,6 +233,7 @@ static inline void cpu_probe_loongson(struct cpuinfo_loongarch *c, unsigned int
>  {
>         uint64_t *vendor = (void *)(&cpu_full_name[VENDOR_OFFSET]);
>         uint64_t *cpuname = (void *)(&cpu_full_name[CPUNAME_OFFSET]);
> +       const char *core_name = "Unknown";
>
>         if (!__cpu_full_name[cpu])
>                 __cpu_full_name[cpu] = cpu_full_name;
> @@ -232,40 +244,43 @@ static inline void cpu_probe_loongson(struct cpuinfo_loongarch *c, unsigned int
>         switch (c->processor_id & PRID_SERIES_MASK) {
>         case PRID_SERIES_LA132:
>                 c->cputype = CPU_LOONGSON32;
> -               set_isa(c, LOONGARCH_CPU_ISA_LA32S);
>                 __cpu_family[cpu] = "Loongson-32bit";
> -               pr_info("32-bit Loongson Processor probed (LA132 Core)\n");
> +               core_name = "LA132";
>                 break;
>         case PRID_SERIES_LA264:
>                 c->cputype = CPU_LOONGSON64;
> -               set_isa(c, LOONGARCH_CPU_ISA_LA64);
>                 __cpu_family[cpu] = "Loongson-64bit";
> -               pr_info("64-bit Loongson Processor probed (LA264 Core)\n");
> +               core_name = "LA264";
>                 break;
>         case PRID_SERIES_LA364:
>                 c->cputype = CPU_LOONGSON64;
> -               set_isa(c, LOONGARCH_CPU_ISA_LA64);
>                 __cpu_family[cpu] = "Loongson-64bit";
> -               pr_info("64-bit Loongson Processor probed (LA364 Core)\n");
> +               core_name = "LA364";
>                 break;
>         case PRID_SERIES_LA464:
>                 c->cputype = CPU_LOONGSON64;
> -               set_isa(c, LOONGARCH_CPU_ISA_LA64);
>                 __cpu_family[cpu] = "Loongson-64bit";
> -               pr_info("64-bit Loongson Processor probed (LA464 Core)\n");
> +               core_name = "LA464";
>                 break;
>         case PRID_SERIES_LA664:
>                 c->cputype = CPU_LOONGSON64;
> -               set_isa(c, LOONGARCH_CPU_ISA_LA64);
>                 __cpu_family[cpu] = "Loongson-64bit";
> -               pr_info("64-bit Loongson Processor probed (LA664 Core)\n");
> +               core_name = "LA664";
>                 break;
>         default: /* Default to 64 bit */
> -               c->cputype = CPU_LOONGSON64;
> -               set_isa(c, LOONGARCH_CPU_ISA_LA64);
> -               __cpu_family[cpu] = "Loongson-64bit";
> -               pr_info("64-bit Loongson Processor probed (Unknown Core)\n");
> +               if (c->isa_level & LOONGARCH_CPU_ISA_LA64) {
> +                       c->cputype = CPU_LOONGSON64;
> +                       __cpu_family[cpu] = "Loongson-64bit";
> +               } else if (c->isa_level & LOONGARCH_CPU_ISA_LA32S) {
> +                       c->cputype = CPU_LOONGSON32;
> +                       __cpu_family[cpu] = "Loongson-32bit";
Change the name to "Loongson-32bit Standard".

Huacai
> +               } else if (c->isa_level & LOONGARCH_CPU_ISA_LA32R) {
> +                       c->cputype = CPU_LOONGSON32;
> +                       __cpu_family[cpu] = "Loongson-32bit Reduced";
> +               }
>         }
> +
> +       pr_info("%s Processor probed (%s Core)\n", __cpu_family[cpu], core_name);
>  }
>
>  #ifdef CONFIG_64BIT
>
> --
> 2.46.0
>