1 files changed, 321 insertions, 0 deletions
diff --git a/arch/mips/kernel/fpu-probe.c b/arch/mips/kernel/fpu-probe.c
new file mode 100644
index 000000000..e689d6a83
--- /dev/null
+++ b/arch/mips/kernel/fpu-probe.c
@@ -0,0 +1,321 @@
+// 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);
+