1 files changed, 41 insertions, 8 deletions

diff --git a/arch/mips/include/asm/fpu.h b/arch/mips/include/asm/fpu.h
index dd562414cd5e..994d21939676 100644
--- a/arch/mips/include/asm/fpu.h
+++ b/arch/mips/include/asm/fpu.h
@@ -36,14 +36,16 @@ extern void _restore_fp(struct task_struct *);
 
 /*
  * This enum specifies a mode in which we want the FPU to operate, for cores
- * which implement the Status.FR bit. Note that FPU_32BIT & FPU_64BIT
- * purposefully have the values 0 & 1 respectively, so that an integer value
- * of Status.FR can be trivially casted to the corresponding enum fpu_mode.
+ * which implement the Status.FR bit. Note that the bottom bit of the value
+ * purposefully matches the desired value of the Status.FR bit.
  */
 enum fpu_mode {
 	FPU_32BIT = 0,		/* FR = 0 */
-	FPU_64BIT,		/* FR = 1 */
+	FPU_64BIT,		/* FR = 1, FRE = 0 */
 	FPU_AS_IS,
+	FPU_HYBRID,		/* FR = 1, FRE = 1 */
+
+#define FPU_FR_MASK		0x1
 };
 
 static inline int __enable_fpu(enum fpu_mode mode)
@@ -57,6 +59,14 @@ static inline int __enable_fpu(enum fpu_mode mode)
 		enable_fpu_hazard();
 		return 0;
 
+	case FPU_HYBRID:
+		if (!cpu_has_fre)
+			return SIGFPE;
+
+		/* set FRE */
+		write_c0_config5(read_c0_config5() | MIPS_CONF5_FRE);
+		goto fr_common;
+
 	case FPU_64BIT:
 #if !(defined(CONFIG_CPU_MIPS32_R2) || defined(CONFIG_64BIT))
 		/* we only have a 32-bit FPU */
@@ -64,8 +74,11 @@ static inline int __enable_fpu(enum fpu_mode mode)
 #endif
 		/* fall through */
 	case FPU_32BIT:
+		/* clear FRE */
+		write_c0_config5(read_c0_config5() & ~MIPS_CONF5_FRE);
+fr_common:
 		/* set CU1 & change FR appropriately */
-		fr = (int)mode;
+		fr = (int)mode & FPU_FR_MASK;
 		change_c0_status(ST0_CU1 | ST0_FR, ST0_CU1 | (fr ? ST0_FR : 0));
 		enable_fpu_hazard();
 
@@ -102,13 +115,17 @@ static inline int __own_fpu(void)
 	enum fpu_mode mode;
 	int ret;
 
-	mode = !test_thread_flag(TIF_32BIT_FPREGS);
+	if (test_thread_flag(TIF_HYBRID_FPREGS))
+		mode = FPU_HYBRID;
+	else
+		mode = !test_thread_flag(TIF_32BIT_FPREGS);
+
 	ret = __enable_fpu(mode);
 	if (ret)
 		return ret;
 
 	KSTK_STATUS(current) |= ST0_CU1;
-	if (mode == FPU_64BIT)
+	if (mode == FPU_64BIT || mode == FPU_HYBRID)
 		KSTK_STATUS(current) |= ST0_FR;
 	else /* mode == FPU_32BIT */
 		KSTK_STATUS(current) &= ~ST0_FR;
@@ -166,8 +183,24 @@ static inline int init_fpu(void)
 
 	if (cpu_has_fpu) {
 		ret = __own_fpu();
-		if (!ret)
+		if (!ret) {
+			unsigned int config5 = read_c0_config5();
+
+			/*
+			 * Ensure FRE is clear whilst running _init_fpu, since
+			 * single precision FP instructions are used. If FRE
+			 * was set then we'll just end up initialising all 32
+			 * 64b registers.
+			 */
+			write_c0_config5(config5 & ~MIPS_CONF5_FRE);
+			enable_fpu_hazard();
+
 			_init_fpu();
+
+			/* Restore FRE */
+			write_c0_config5(config5);
+			enable_fpu_hazard();
+		}
 	} else
 		fpu_emulator_init_fpu();