xref: /openbmc/linux/arch/riscv/kernel/cpufeature.c (revision 86edee97)
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 }
75