--- zzzz-none-000/linux-3.10.107/arch/powerpc/math-emu/math.c	2017-06-27 09:49:32.000000000 +0000
+++ scorpion-7490-727/linux-3.10.107/arch/powerpc/math-emu/math.c	2021-02-04 17:41:59.000000000 +0000
@@ -7,12 +7,27 @@
 
 #include <asm/uaccess.h>
 #include <asm/reg.h>
+#include <asm/switch_to.h>
 
 #include <asm/sfp-machine.h>
 #include <math-emu/double.h>
 
 #define FLOATFUNC(x)	extern int x(void *, void *, void *, void *)
 
+/* The instructions list which may be not implemented by a hardware FPU */
+FLOATFUNC(fre);
+FLOATFUNC(frsqrtes);
+FLOATFUNC(fsqrt);
+FLOATFUNC(fsqrts);
+FLOATFUNC(mtfsf);
+FLOATFUNC(mtfsfi);
+
+#ifdef CONFIG_MATH_EMULATION_HW_UNIMPLEMENTED
+#undef FLOATFUNC(x)
+#define FLOATFUNC(x)	static inline int x(void *op1, void *op2, void *op3, \
+						 void *op4) { }
+#endif
+
 FLOATFUNC(fadd);
 FLOATFUNC(fadds);
 FLOATFUNC(fdiv);
@@ -42,8 +57,6 @@
 FLOATFUNC(mffs);
 FLOATFUNC(mtfsb0);
 FLOATFUNC(mtfsb1);
-FLOATFUNC(mtfsf);
-FLOATFUNC(mtfsfi);
 
 FLOATFUNC(lfd);
 FLOATFUNC(lfs);
@@ -61,8 +74,6 @@
 FLOATFUNC(fres);
 FLOATFUNC(frsqrte);
 FLOATFUNC(fsel);
-FLOATFUNC(fsqrt);
-FLOATFUNC(fsqrts);
 
 
 #define OP31		0x1f		/*   31 */
@@ -97,6 +108,7 @@
 #define FSQRTS		0x016		/*   22 */
 #define FRES		0x018		/*   24 */
 #define FMULS		0x019		/*   25 */
+#define FRSQRTES	0x01a		/*   26 */
 #define FMSUBS		0x01c		/*   28 */
 #define FMADDS		0x01d		/*   29 */
 #define FNMSUBS		0x01e		/*   30 */
@@ -109,6 +121,7 @@
 #define FADD		0x015		/*   21 */
 #define FSQRT		0x016		/*   22 */
 #define FSEL		0x017		/*   23 */
+#define FRE		0x018		/*   24 */
 #define FMUL		0x019		/*   25 */
 #define FRSQRTE		0x01a		/*   26 */
 #define FMSUB		0x01c		/*   28 */
@@ -150,7 +163,6 @@
 #define XEU	15
 #define XFLB	10
 
-#ifdef CONFIG_MATH_EMULATION
 static int
 record_exception(struct pt_regs *regs, int eflag)
 {
@@ -208,7 +220,6 @@
 
 	return (fpscr & FPSCR_FEX) ? 1 : 0;
 }
-#endif /* CONFIG_MATH_EMULATION */
 
 int
 do_mathemu(struct pt_regs *regs)
@@ -218,56 +229,13 @@
 	signed short sdisp;
 	u32 insn = 0;
 	int idx = 0;
-#ifdef CONFIG_MATH_EMULATION
 	int (*func)(void *, void *, void *, void *);
 	int type = 0;
 	int eflag, trap;
-#endif
 
 	if (get_user(insn, (u32 *)pc))
 		return -EFAULT;
 
-#ifndef CONFIG_MATH_EMULATION
-	switch (insn >> 26) {
-	case LFD:
-		idx = (insn >> 16) & 0x1f;
-		sdisp = (insn & 0xffff);
-		op0 = (void *)&current->thread.TS_FPR((insn >> 21) & 0x1f);
-		op1 = (void *)((idx ? regs->gpr[idx] : 0) + sdisp);
-		lfd(op0, op1, op2, op3);
-		break;
-	case LFDU:
-		idx = (insn >> 16) & 0x1f;
-		sdisp = (insn & 0xffff);
-		op0 = (void *)&current->thread.TS_FPR((insn >> 21) & 0x1f);
-		op1 = (void *)((idx ? regs->gpr[idx] : 0) + sdisp);
-		lfd(op0, op1, op2, op3);
-		regs->gpr[idx] = (unsigned long)op1;
-		break;
-	case STFD:
-		idx = (insn >> 16) & 0x1f;
-		sdisp = (insn & 0xffff);
-		op0 = (void *)&current->thread.TS_FPR((insn >> 21) & 0x1f);
-		op1 = (void *)((idx ? regs->gpr[idx] : 0) + sdisp);
-		stfd(op0, op1, op2, op3);
-		break;
-	case STFDU:
-		idx = (insn >> 16) & 0x1f;
-		sdisp = (insn & 0xffff);
-		op0 = (void *)&current->thread.TS_FPR((insn >> 21) & 0x1f);
-		op1 = (void *)((idx ? regs->gpr[idx] : 0) + sdisp);
-		stfd(op0, op1, op2, op3);
-		regs->gpr[idx] = (unsigned long)op1;
-		break;
-	case OP63:
-		op0 = (void *)&current->thread.TS_FPR((insn >> 21) & 0x1f);
-		op1 = (void *)&current->thread.TS_FPR((insn >> 11) & 0x1f);
-		fmr(op0, op1, op2, op3);
-		break;
-	default:
-		goto illegal;
-	}
-#else /* CONFIG_MATH_EMULATION */
 	switch (insn >> 26) {
 	case LFS:	func = lfs;	type = D;	break;
 	case LFSU:	func = lfs;	type = DU;	break;
@@ -299,9 +267,10 @@
 		case FDIVS:	func = fdivs;	type = AB;	break;
 		case FSUBS:	func = fsubs;	type = AB;	break;
 		case FADDS:	func = fadds;	type = AB;	break;
-		case FSQRTS:	func = fsqrts;	type = AB;	break;
-		case FRES:	func = fres;	type = AB;	break;
+		case FSQRTS:	func = fsqrts;	type = XB;	break;
+		case FRES:	func = fres;	type = XB;	break;
 		case FMULS:	func = fmuls;	type = AC;	break;
+		case FRSQRTES:	func = frsqrtes;type = XB;	break;
 		case FMSUBS:	func = fmsubs;	type = ABC;	break;
 		case FMADDS:	func = fmadds;	type = ABC;	break;
 		case FNMSUBS:	func = fnmsubs;	type = ABC;	break;
@@ -317,10 +286,11 @@
 			case FDIV:	func = fdiv;	type = AB;	break;
 			case FSUB:	func = fsub;	type = AB;	break;
 			case FADD:	func = fadd;	type = AB;	break;
-			case FSQRT:	func = fsqrt;	type = AB;	break;
+			case FSQRT:	func = fsqrt;	type = XB;	break;
+			case FRE:	func = fre;	type = XB;	break;
 			case FSEL:	func = fsel;	type = ABC;	break;
 			case FMUL:	func = fmul;	type = AC;	break;
-			case FRSQRTE:	func = frsqrte;	type = AB;	break;
+			case FRSQRTE:	func = frsqrte;	type = XB;	break;
 			case FMSUB:	func = fmsub;	type = ABC;	break;
 			case FMADD:	func = fmadd;	type = ABC;	break;
 			case FNMSUB:	func = fnmsub;	type = ABC;	break;
@@ -410,21 +380,16 @@
 	case XE:
 		idx = (insn >> 16) & 0x1f;
 		op0 = (void *)&current->thread.TS_FPR((insn >> 21) & 0x1f);
-		if (!idx) {
-			if (((insn >> 1) & 0x3ff) == STFIWX)
-				op1 = (void *)(regs->gpr[(insn >> 11) & 0x1f]);
-			else
-				goto illegal;
-		} else {
-			op1 = (void *)(regs->gpr[idx] + regs->gpr[(insn >> 11) & 0x1f]);
-		}
-
+		op1 = (void *)((idx ? regs->gpr[idx] : 0)
+				+ regs->gpr[(insn >> 11) & 0x1f]);
 		break;
 
 	case XEU:
 		idx = (insn >> 16) & 0x1f;
+		if (!idx)
+			goto illegal;
 		op0 = (void *)&current->thread.TS_FPR((insn >> 21) & 0x1f);
-		op1 = (void *)((idx ? regs->gpr[idx] : 0)
+		op1 = (void *)(regs->gpr[idx]
 				+ regs->gpr[(insn >> 11) & 0x1f]);
 		break;
 
@@ -459,6 +424,13 @@
 		goto illegal;
 	}
 
+	/*
+	 * If we support a HW FPU, we need to ensure the FP state
+	 * is flushed into the thread_struct before attempting
+	 * emulation
+	 */
+	flush_fp_to_thread(current);
+
 	eflag = func(op0, op1, op2, op3);
 
 	if (insn & 1) {
@@ -479,7 +451,6 @@
 	default:
 		break;
 	}
-#endif /* CONFIG_MATH_EMULATION */
 
 	regs->nip += 4;
 	return 0;