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mirror_ubuntu-kernels/arch/mips/kernel/fpu-probe.c

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// 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 <asm/bugs.h>
#include <asm/cpu.h>
#include <asm/cpu-features.h>
#include <asm/cpu-type.h>
#include <asm/elf.h>
#include <asm/fpu.h>
#include <asm/mipsregs.h>
#include "fpu-probe.h"
/*
* Get the FPU Implementation/Revision.
*/
static inline unsigned long cpu_get_fpu_id(void)
{
unsigned long tmp, fpu_id;
tmp = read_c0_status();
__enable_fpu(FPU_AS_IS);
fpu_id = read_32bit_cp1_register(CP1_REVISION);
write_c0_status(tmp);
return fpu_id;
}
/*
* Check if the CPU has an external FPU.
*/
int __cpu_has_fpu(void)
{
return (cpu_get_fpu_id() & FPIR_IMP_MASK) != FPIR_IMP_NONE;
}
/*
* Determine the FCSR mask for FPU hardware.
*/
static inline void cpu_set_fpu_fcsr_mask(struct cpuinfo_mips *c)
{
unsigned long sr, mask, fcsr, fcsr0, fcsr1;
fcsr = c->fpu_csr31;
mask = FPU_CSR_ALL_X | FPU_CSR_ALL_E | FPU_CSR_ALL_S | FPU_CSR_RM;
sr = read_c0_status();
__enable_fpu(FPU_AS_IS);
fcsr0 = fcsr & mask;
write_32bit_cp1_register(CP1_STATUS, fcsr0);
fcsr0 = read_32bit_cp1_register(CP1_STATUS);
fcsr1 = fcsr | ~mask;
write_32bit_cp1_register(CP1_STATUS, fcsr1);
fcsr1 = read_32bit_cp1_register(CP1_STATUS);
write_32bit_cp1_register(CP1_STATUS, fcsr);
write_c0_status(sr);
c->fpu_msk31 = ~(fcsr0 ^ fcsr1) & ~mask;
}
/*
* Determine the IEEE 754 NaN encodings and ABS.fmt/NEG.fmt execution modes
* supported by FPU hardware.
*/
static void cpu_set_fpu_2008(struct cpuinfo_mips *c)
{
if (c->isa_level & (MIPS_CPU_ISA_M32R1 | MIPS_CPU_ISA_M64R1 |
MIPS_CPU_ISA_M32R2 | MIPS_CPU_ISA_M64R2 |
MIPS_CPU_ISA_M32R5 | MIPS_CPU_ISA_M64R5 |
MIPS_CPU_ISA_M32R6 | MIPS_CPU_ISA_M64R6)) {
unsigned long sr, fir, fcsr, fcsr0, fcsr1;
sr = read_c0_status();
__enable_fpu(FPU_AS_IS);
fir = read_32bit_cp1_register(CP1_REVISION);
if (fir & MIPS_FPIR_HAS2008) {
fcsr = read_32bit_cp1_register(CP1_STATUS);
/*
* MAC2008 toolchain never landed in real world, so
* we're only testing whether it can be disabled and
* don't try to enabled it.
*/
fcsr0 = fcsr & ~(FPU_CSR_ABS2008 | FPU_CSR_NAN2008 |
FPU_CSR_MAC2008);
write_32bit_cp1_register(CP1_STATUS, fcsr0);
fcsr0 = read_32bit_cp1_register(CP1_STATUS);
fcsr1 = fcsr | FPU_CSR_ABS2008 | FPU_CSR_NAN2008;
write_32bit_cp1_register(CP1_STATUS, fcsr1);
fcsr1 = read_32bit_cp1_register(CP1_STATUS);
write_32bit_cp1_register(CP1_STATUS, fcsr);
if (c->isa_level & (MIPS_CPU_ISA_M32R2 |
MIPS_CPU_ISA_M64R2)) {
/*
* The bit for MAC2008 might be reused by R6
* in future, so we only test for R2-R5.
*/
if (fcsr0 & FPU_CSR_MAC2008)
c->options |= MIPS_CPU_MAC_2008_ONLY;
}
if (!(fcsr0 & FPU_CSR_NAN2008))
c->options |= MIPS_CPU_NAN_LEGACY;
if (fcsr1 & FPU_CSR_NAN2008)
c->options |= MIPS_CPU_NAN_2008;
if ((fcsr0 ^ fcsr1) & FPU_CSR_ABS2008)
c->fpu_msk31 &= ~FPU_CSR_ABS2008;
else
c->fpu_csr31 |= fcsr & FPU_CSR_ABS2008;
if ((fcsr0 ^ fcsr1) & FPU_CSR_NAN2008)
c->fpu_msk31 &= ~FPU_CSR_NAN2008;
else
c->fpu_csr31 |= fcsr & FPU_CSR_NAN2008;
} else {
c->options |= MIPS_CPU_NAN_LEGACY;
}
write_c0_status(sr);
} else {
c->options |= MIPS_CPU_NAN_LEGACY;
}
}
/*
* IEEE 754 conformance mode to use. Affects the NaN encoding and the
* ABS.fmt/NEG.fmt execution mode.
*/
static enum { STRICT, LEGACY, STD2008, RELAXED } ieee754 = STRICT;
/*
* Set the IEEE 754 NaN encodings and the ABS.fmt/NEG.fmt execution modes
* to support by the FPU emulator according to the IEEE 754 conformance
* mode selected. Note that "relaxed" straps the emulator so that it
* allows 2008-NaN binaries even for legacy processors.
*/
static void cpu_set_nofpu_2008(struct cpuinfo_mips *c)
{
c->options &= ~(MIPS_CPU_NAN_2008 | MIPS_CPU_NAN_LEGACY);
c->fpu_csr31 &= ~(FPU_CSR_ABS2008 | FPU_CSR_NAN2008);
c->fpu_msk31 &= ~(FPU_CSR_ABS2008 | FPU_CSR_NAN2008);
switch (ieee754) {
case STRICT:
if (c->isa_level & (MIPS_CPU_ISA_M32R1 | MIPS_CPU_ISA_M64R1 |
MIPS_CPU_ISA_M32R2 | MIPS_CPU_ISA_M64R2 |
MIPS_CPU_ISA_M32R5 | MIPS_CPU_ISA_M64R5 |
MIPS_CPU_ISA_M32R6 | MIPS_CPU_ISA_M64R6)) {
c->options |= MIPS_CPU_NAN_2008 | MIPS_CPU_NAN_LEGACY;
} else {
c->options |= MIPS_CPU_NAN_LEGACY;
c->fpu_msk31 |= FPU_CSR_ABS2008 | FPU_CSR_NAN2008;
}
break;
case LEGACY:
c->options |= MIPS_CPU_NAN_LEGACY;
c->fpu_msk31 |= FPU_CSR_ABS2008 | FPU_CSR_NAN2008;
break;
case STD2008:
c->options |= MIPS_CPU_NAN_2008;
c->fpu_csr31 |= FPU_CSR_ABS2008 | FPU_CSR_NAN2008;
c->fpu_msk31 |= FPU_CSR_ABS2008 | FPU_CSR_NAN2008;
break;
case RELAXED:
c->options |= MIPS_CPU_NAN_2008 | MIPS_CPU_NAN_LEGACY;
break;
}
}
/*
* Override the IEEE 754 NaN encoding and ABS.fmt/NEG.fmt execution mode
* according to the "ieee754=" parameter.
*/
static void cpu_set_nan_2008(struct cpuinfo_mips *c)
{
switch (ieee754) {
case STRICT:
mips_use_nan_legacy = !!cpu_has_nan_legacy;
mips_use_nan_2008 = !!cpu_has_nan_2008;
break;
case LEGACY:
mips_use_nan_legacy = !!cpu_has_nan_legacy;
mips_use_nan_2008 = !cpu_has_nan_legacy;
break;
case STD2008:
mips_use_nan_legacy = !cpu_has_nan_2008;
mips_use_nan_2008 = !!cpu_has_nan_2008;
break;
case RELAXED:
mips_use_nan_legacy = true;
mips_use_nan_2008 = true;
break;
}
}
/*
* IEEE 754 NaN encoding and ABS.fmt/NEG.fmt execution mode override
* settings:
*
* strict: accept binaries that request a NaN encoding supported by the FPU
* legacy: only accept legacy-NaN binaries
* 2008: only accept 2008-NaN binaries
* relaxed: accept any binaries regardless of whether supported by the FPU
*/
static int __init ieee754_setup(char *s)
{
if (!s)
return -1;
else if (!strcmp(s, "strict"))
ieee754 = STRICT;
else if (!strcmp(s, "legacy"))
ieee754 = LEGACY;
else if (!strcmp(s, "2008"))
ieee754 = STD2008;
else if (!strcmp(s, "relaxed"))
ieee754 = RELAXED;
else
return -1;
if (!(boot_cpu_data.options & MIPS_CPU_FPU))
cpu_set_nofpu_2008(&boot_cpu_data);
cpu_set_nan_2008(&boot_cpu_data);
return 0;
}
early_param("ieee754", ieee754_setup);
/*
* Set the FIR feature flags for the FPU emulator.
*/
static void cpu_set_nofpu_id(struct cpuinfo_mips *c)
{
u32 value;
value = 0;
if (c->isa_level & (MIPS_CPU_ISA_M32R1 | MIPS_CPU_ISA_M64R1 |
MIPS_CPU_ISA_M32R2 | MIPS_CPU_ISA_M64R2 |
MIPS_CPU_ISA_M32R5 | MIPS_CPU_ISA_M64R5 |
MIPS_CPU_ISA_M32R6 | MIPS_CPU_ISA_M64R6))
value |= MIPS_FPIR_D | MIPS_FPIR_S;
if (c->isa_level & (MIPS_CPU_ISA_M32R2 | MIPS_CPU_ISA_M64R2 |
MIPS_CPU_ISA_M32R5 | MIPS_CPU_ISA_M64R5 |
MIPS_CPU_ISA_M32R6 | MIPS_CPU_ISA_M64R6))
value |= MIPS_FPIR_F64 | MIPS_FPIR_L | MIPS_FPIR_W;
if (c->options & MIPS_CPU_NAN_2008)
value |= MIPS_FPIR_HAS2008;
c->fpu_id = value;
}
/* Determined FPU emulator mask to use for the boot CPU with "nofpu". */
static unsigned int mips_nofpu_msk31;
/*
* Set options for FPU hardware.
*/
void cpu_set_fpu_opts(struct cpuinfo_mips *c)
{
c->fpu_id = cpu_get_fpu_id();
mips_nofpu_msk31 = c->fpu_msk31;
if (c->isa_level & (MIPS_CPU_ISA_M32R1 | MIPS_CPU_ISA_M64R1 |
MIPS_CPU_ISA_M32R2 | MIPS_CPU_ISA_M64R2 |
MIPS_CPU_ISA_M32R5 | MIPS_CPU_ISA_M64R5 |
MIPS_CPU_ISA_M32R6 | MIPS_CPU_ISA_M64R6)) {
if (c->fpu_id & MIPS_FPIR_3D)
c->ases |= MIPS_ASE_MIPS3D;
if (c->fpu_id & MIPS_FPIR_UFRP)
c->options |= MIPS_CPU_UFR;
if (c->fpu_id & MIPS_FPIR_FREP)
c->options |= MIPS_CPU_FRE;
}
cpu_set_fpu_fcsr_mask(c);
cpu_set_fpu_2008(c);
cpu_set_nan_2008(c);
}
/*
* Set options for the FPU emulator.
*/
void cpu_set_nofpu_opts(struct cpuinfo_mips *c)
{
c->options &= ~MIPS_CPU_FPU;
c->fpu_msk31 = mips_nofpu_msk31;
cpu_set_nofpu_2008(c);
cpu_set_nan_2008(c);
cpu_set_nofpu_id(c);
}
int mips_fpu_disabled;
static int __init fpu_disable(char *s)
{
cpu_set_nofpu_opts(&boot_cpu_data);
mips_fpu_disabled = 1;
return 1;
}
__setup("nofpu", fpu_disable);
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