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 #include <asm/switch_to.h>
  14
  15 unsigned long elf_hwcap __read_mostly;
  16 #ifdef CONFIG_FPU
  17 bool has_fpu __read_mostly;
  18 #endif
  19
  20 void riscv_fill_hwcap(void)
  21 {
  22         struct device_node *node;
  23         const char *isa;
  24         size_t i;
  25         static unsigned long isa2hwcap[256] = {0};
  26
  27         isa2hwcap['i'] = isa2hwcap['I'] = COMPAT_HWCAP_ISA_I;
  28         isa2hwcap['m'] = isa2hwcap['M'] = COMPAT_HWCAP_ISA_M;
  29         isa2hwcap['a'] = isa2hwcap['A'] = COMPAT_HWCAP_ISA_A;
  30         isa2hwcap['f'] = isa2hwcap['F'] = COMPAT_HWCAP_ISA_F;
  31         isa2hwcap['d'] = isa2hwcap['D'] = COMPAT_HWCAP_ISA_D;
  32         isa2hwcap['c'] = isa2hwcap['C'] = COMPAT_HWCAP_ISA_C;
  33
  34         elf_hwcap = 0;
  35
  36         for_each_of_cpu_node(node) {
  37                 unsigned long this_hwcap = 0;
  38
  39                 if (riscv_of_processor_hartid(node) < 0)
  40                         continue;
  41
  42                 if (of_property_read_string(node, "riscv,isa", &isa)) {
  43                         pr_warn("Unable to find \"riscv,isa\" devicetree entry\n");
  44                         continue;
  45                 }
  46
  47                 for (i = 0; i < strlen(isa); ++i)
  48                         this_hwcap |= isa2hwcap[(unsigned char)(isa[i])];
  49
  50                 /*
  51                  * All "okay" hart should have same isa. Set HWCAP based on
  52                  * common capabilities of every "okay" hart, in case they don't
  53                  * have.
  54                  */
  55                 if (elf_hwcap)
  56                         elf_hwcap &= this_hwcap;
  57                 else
  58                         elf_hwcap = this_hwcap;
  59         }
  60
  61         /* We don't support systems with F but without D, so mask those out
  62          * here. */
  63         if ((elf_hwcap & COMPAT_HWCAP_ISA_F) && !(elf_hwcap & COMPAT_HWCAP_ISA_D)) {
  64                 pr_info("This kernel does not support systems with F but not D\n");
  65                 elf_hwcap &= ~COMPAT_HWCAP_ISA_F;
  66         }
  67
  68         pr_info("elf_hwcap is 0x%lx\n", elf_hwcap);
  69
  70 #ifdef CONFIG_FPU
  71         if (elf_hwcap & (COMPAT_HWCAP_ISA_F | COMPAT_HWCAP_ISA_D))
  72                 has_fpu = true;
  73 #endif
  74 }