linux/linux-5.18.11/arch/mips/kernel/cpu-r3k-probe.c

// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * Processor capabilities determination functions.
 *
 * Copyright (C) xxxx  the Anonymous
 * Copyright (C) 1994 - 2006 Ralf Baechle
 * Copyright (C) 2003, 2004  Maciej W. Rozycki
 * Copyright (C) 2001, 2004, 2011, 2012	 MIPS Technologies, Inc.
 */
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/ptrace.h>
#include <linux/smp.h>
#include <linux/stddef.h>
#include <linux/export.h>

#include <asm/bugs.h>
#include <asm/cpu.h>
#include <asm/cpu-features.h>
#include <asm/cpu-type.h>
#include <asm/fpu.h>
#include <asm/mipsregs.h>
#include <asm/elf.h>
#include <asm/traps.h>

#include "fpu-probe.h"

/* Hardware capabilities */
unsigned int elf_hwcap __read_mostly;
EXPORT_SYMBOL_GPL(elf_hwcap);

void __init check_bugs32(void)
{

}

/*
 * Probe whether cpu has config register by trying to play with
 * alternate cache bit and see whether it matters.
 * It's used by cpu_probe to distinguish between R3000A and R3081.
 */
static inline int cpu_has_confreg(void)
{
#ifdef CONFIG_CPU_R3000
	extern unsigned long r3k_cache_size(unsigned long);
	unsigned long size1, size2;
	unsigned long cfg = read_c0_conf();

	size1 = r3k_cache_size(ST0_ISC);
	write_c0_conf(cfg ^ R30XX_CONF_AC);
	size2 = r3k_cache_size(ST0_ISC);
	write_c0_conf(cfg);
	return size1 != size2;
#else
	return 0;
#endif
}

static inline void set_elf_platform(int cpu, const char *plat)
{
	if (cpu == 0)
		__elf_platform = plat;
}

const char *__cpu_name[NR_CPUS];
const char *__elf_platform;
const char *__elf_base_platform;

void cpu_probe(void)
{
	struct cpuinfo_mips *c = &current_cpu_data;
	unsigned int cpu = smp_processor_id();

	/*
	 * Set a default elf platform, cpu probe may later
	 * overwrite it with a more precise value
	 */
	set_elf_platform(cpu, "mips");

	c->processor_id = PRID_IMP_UNKNOWN;
	c->fpu_id	= FPIR_IMP_NONE;
	c->cputype	= CPU_UNKNOWN;
	c->writecombine = _CACHE_UNCACHED;

	c->fpu_csr31	= FPU_CSR_RN;
	c->fpu_msk31	= FPU_CSR_RSVD | FPU_CSR_ABS2008 | FPU_CSR_NAN2008 |
			  FPU_CSR_CONDX | FPU_CSR_FS;

	c->srsets = 1;

	c->processor_id = read_c0_prid();
	switch (c->processor_id & (PRID_COMP_MASK | PRID_IMP_MASK)) {
	case PRID_COMP_LEGACY | PRID_IMP_R2000:
		c->cputype = CPU_R2000;
		__cpu_name[cpu] = "R2000";
		c->options = MIPS_CPU_TLB | MIPS_CPU_3K_CACHE |
			     MIPS_CPU_NOFPUEX;
		if (__cpu_has_fpu())
			c->options |= MIPS_CPU_FPU;
		c->tlbsize = 64;
		break;
	case PRID_COMP_LEGACY | PRID_IMP_R3000:
		if ((c->processor_id & PRID_REV_MASK) == PRID_REV_R3000A) {
			if (cpu_has_confreg()) {
				c->cputype = CPU_R3081E;
				__cpu_name[cpu] = "R3081";
			} else {
				c->cputype = CPU_R3000A;
				__cpu_name[cpu] = "R3000A";
			}
		} else {
			c->cputype = CPU_R3000;
			__cpu_name[cpu] = "R3000";
		}
		c->options = MIPS_CPU_TLB | MIPS_CPU_3K_CACHE |
			     MIPS_CPU_NOFPUEX;
		if (__cpu_has_fpu())
			c->options |= MIPS_CPU_FPU;
		c->tlbsize = 64;
		break;
	}

	BUG_ON(!__cpu_name[cpu]);
	BUG_ON(c->cputype == CPU_UNKNOWN);

	/*
	 * Platform code can force the cpu type to optimize code
	 * generation. In that case be sure the cpu type is correctly
	 * manually setup otherwise it could trigger some nasty bugs.
	 */
	BUG_ON(current_cpu_type() != c->cputype);

	if (mips_fpu_disabled)
		c->options &= ~MIPS_CPU_FPU;

	if (c->options & MIPS_CPU_FPU)
		cpu_set_fpu_opts(c);
	else
		cpu_set_nofpu_opts(c);

	reserve_exception_space(0, 0x400);
}

void cpu_report(void)
{
	struct cpuinfo_mips *c = &current_cpu_data;

	pr_info("CPU%d revision is: %08x (%s)\n",
		smp_processor_id(), c->processor_id, cpu_name_string());
	if (c->options & MIPS_CPU_FPU)
		pr_info("FPU revision is: %08x\n", c->fpu_id);
}