arch/riscv/kernel/cpufeature.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * Copied from arch/arm64/kernel/cpufeature.c
   4  *
   5  * Copyright (C) 2015 ARM Ltd.
   6  * Copyright (C) 2017 SiFive
   7  */
   8
   9 #include <linux/of.h>
  10 #include <asm/processor.h>
  11 #include <asm/hwcap.h>
  12 #include <asm/smp.h>
  13
  14 unsigned long elf_hwcap __read_mostly;
  15 #ifdef CONFIG_FPU
  16 bool has_fpu __read_mostly;
  17 #endif
  18
  19 void riscv_fill_hwcap(void)
  20 {
  21         struct device_node *node;
  22         const char *isa;
  23         size_t i;
  24         static unsigned long isa2hwcap[256] = {0};
  25
  26         isa2hwcap['i'] = isa2hwcap['I'] = COMPAT_HWCAP_ISA_I;
  27         isa2hwcap['m'] = isa2hwcap['M'] = COMPAT_HWCAP_ISA_M;
  28         isa2hwcap['a'] = isa2hwcap['A'] = COMPAT_HWCAP_ISA_A;
  29         isa2hwcap['f'] = isa2hwcap['F'] = COMPAT_HWCAP_ISA_F;
  30         isa2hwcap['d'] = isa2hwcap['D'] = COMPAT_HWCAP_ISA_D;
  31         isa2hwcap['c'] = isa2hwcap['C'] = COMPAT_HWCAP_ISA_C;
  32
  33         elf_hwcap = 0;
  34
  35         for_each_of_cpu_node(node) {
  36                 unsigned long this_hwcap = 0;
  37
  38                 if (riscv_of_processor_hartid(node) < 0)
  39                         continue;
  40
  41                 if (of_property_read_string(node, "riscv,isa", &isa)) {
  42                         pr_warn("Unable to find \"riscv,isa\" devicetree entry\n");
  43                         continue;
  44                 }
  45
  46                 for (i = 0; i < strlen(isa); ++i)
  47                         this_hwcap |= isa2hwcap[(unsigned char)(isa[i])];
  48
  49                 /*
  50                  * All "okay" hart should have same isa. Set HWCAP based on
  51                  * common capabilities of every "okay" hart, in case they don't
  52                  * have.
  53                  */
  54                 if (elf_hwcap)
  55                         elf_hwcap &= this_hwcap;
  56                 else
  57                         elf_hwcap = this_hwcap;
  58         }
  59
  60         /* We don't support systems with F but without D, so mask those out
  61          * here. */
  62         if ((elf_hwcap & COMPAT_HWCAP_ISA_F) && !(elf_hwcap & COMPAT_HWCAP_ISA_D)) {
  63                 pr_info("This kernel does not support systems with F but not D\n");
  64                 elf_hwcap &= ~COMPAT_HWCAP_ISA_F;
  65         }
  66
  67         pr_info("elf_hwcap is 0x%lx\n", elf_hwcap);
  68
  69 #ifdef CONFIG_FPU
  70         if (elf_hwcap & (COMPAT_HWCAP_ISA_F | COMPAT_HWCAP_ISA_D))
  71                 has_fpu = true;
  72 #endif
  73 }