arch/riscv/kernel/cpufeature.c

   1 /*
   2  * Copied from arch/arm64/kernel/cpufeature.c
   3  *
   4  * Copyright (C) 2015 ARM Ltd.
   5  * Copyright (C) 2017 SiFive
   6  *
   7  * This program is free software; you can redistribute it and/or modify
   8  * it under the terms of the GNU General Public License version 2 as
   9  * published by the Free Software Foundation.
  10  *
  11  * This program is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14  * GNU General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU General Public License
  17  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  18  */
  19
  20 #include <linux/of.h>
  21 #include <asm/processor.h>
  22 #include <asm/hwcap.h>
  23
  24 unsigned long elf_hwcap __read_mostly;
  25 #ifdef CONFIG_FPU
  26 bool has_fpu __read_mostly;
  27 #endif
  28
  29 void riscv_fill_hwcap(void)
  30 {
  31         struct device_node *node;
  32         const char *isa;
  33         size_t i;
  34         static unsigned long isa2hwcap[256] = {0};
  35
  36         isa2hwcap['i'] = isa2hwcap['I'] = COMPAT_HWCAP_ISA_I;
  37         isa2hwcap['m'] = isa2hwcap['M'] = COMPAT_HWCAP_ISA_M;
  38         isa2hwcap['a'] = isa2hwcap['A'] = COMPAT_HWCAP_ISA_A;
  39         isa2hwcap['f'] = isa2hwcap['F'] = COMPAT_HWCAP_ISA_F;
  40         isa2hwcap['d'] = isa2hwcap['D'] = COMPAT_HWCAP_ISA_D;
  41         isa2hwcap['c'] = isa2hwcap['C'] = COMPAT_HWCAP_ISA_C;
  42
  43         elf_hwcap = 0;
  44
  45         /*
  46          * We don't support running Linux on hertergenous ISA systems.  For
  47          * now, we just check the ISA of the first processor.
  48          */
  49         node = of_find_node_by_type(NULL, "cpu");
  50         if (!node) {
  51                 pr_warning("Unable to find \"cpu\" devicetree entry");
  52                 return;
  53         }
  54
  55         if (of_property_read_string(node, "riscv,isa", &isa)) {
  56                 pr_warning("Unable to find \"riscv,isa\" devicetree entry");
  57                 return;
  58         }
  59
  60         for (i = 0; i < strlen(isa); ++i)
  61                 elf_hwcap |= isa2hwcap[(unsigned char)(isa[i])];
  62
  63         /* We don't support systems with F but without D, so mask those out
  64          * here. */
  65         if ((elf_hwcap & COMPAT_HWCAP_ISA_F) && !(elf_hwcap & COMPAT_HWCAP_ISA_D)) {
  66                 pr_info("This kernel does not support systems with F but not D");
  67                 elf_hwcap &= ~COMPAT_HWCAP_ISA_F;
  68         }
  69
  70         pr_info("elf_hwcap is 0x%lx", elf_hwcap);
  71
  72 #ifdef CONFIG_FPU
  73         if (elf_hwcap & (COMPAT_HWCAP_ISA_F | COMPAT_HWCAP_ISA_D))
  74                 has_fpu = true;
  75 #endif
  76 }