[PATCH 3.16 099/254] MIPS: math-emu: Define IEEE 754-2008 feature control bits

[Ben Hutchings]

3.16.55-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: "Maciej W. Rozycki" <macro@xxxxxxxxxxxxxx>

commit f1f3b7ebac08161761c352fd070cfa07b7b94c54 upstream.

Define IEEE 754-2008 feature control bits: FIR.HAS2008, FCSR.ABS2008 and
FCSR.NAN2008, and update the `_ieee754_csr' structure accordingly.

For completeness define FIR.UFRP too.

Signed-off-by: Maciej W. Rozycki <macro@xxxxxxxxxxxxxx>
Cc: linux-mips@xxxxxxxxxxxxxx
Patchwork: https://patchwork.linux-mips.org/patch/9709/
Signed-off-by: Ralf Baechle <ralf@xxxxxxxxxxxxxx>
[bwh: Backported to 3.16: In cop1Emulate(), keep converting the rounding mode]
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
--- a/arch/mips/include/asm/mipsregs.h
+++ b/arch/mips/include/asm/mipsregs.h
@@ -136,10 +136,13 @@
 #define FPU_CSR_COND7	0x80000000	/* $fcc7 */
 
 /*
- * Bits 18 - 20 of the FPU Status Register will be read as 0,
+ * Bits 22:20 of the FPU Status Register will be read as 0,
  * and should be written as zero.
  */
-#define FPU_CSR_RSVD	0x001c0000
+#define FPU_CSR_RSVD	(_ULCAST_(7) << 20)
+
+#define FPU_CSR_ABS2008	(_ULCAST_(1) << 19)
+#define FPU_CSR_NAN2008	(_ULCAST_(1) << 18)
 
 /*
  * X the exception cause indicator
@@ -687,6 +690,8 @@
 #define MIPS_FPIR_W		(_ULCAST_(1) << 20)
 #define MIPS_FPIR_L		(_ULCAST_(1) << 21)
 #define MIPS_FPIR_F64		(_ULCAST_(1) << 22)
+#define MIPS_FPIR_HAS2008	(_ULCAST_(1) << 23)
+#define MIPS_FPIR_UFRP		(_ULCAST_(1) << 28)
 
 /*
  * Bits in the MIPS32 Memory Segmentation registers.
--- a/arch/mips/math-emu/cp1emu.c
+++ b/arch/mips/math-emu/cp1emu.c
@@ -929,10 +929,12 @@ emul:
 					 MIPSInst_RT(ir), value);
 
 				/*
-				 * Don't write reserved bits,
+				 * Don't write unsupported bits,
 				 * and convert to ieee library modes
 				 */
-				ctx->fcr31 = (value & ~(FPU_CSR_RSVD | FPU_CSR_RM)) |
+				ctx->fcr31 = (value &
+					      ~(FPU_CSR_RSVD | FPU_CSR_ABS2008 |
+						FPU_CSR_NAN2008 | FPU_CSR_RM)) |
 					     modeindex(value);
 			}
 			if ((ctx->fcr31 >> 5) & ctx->fcr31 & FPU_CSR_ALL_E) {
--- a/arch/mips/math-emu/ieee754.h
+++ b/arch/mips/math-emu/ieee754.h
@@ -195,15 +195,17 @@ static inline int ieee754dp_ge(union iee
  * The control status register
  */
 struct _ieee754_csr {
-	__BITFIELD_FIELD(unsigned pad0:7,
-	__BITFIELD_FIELD(unsigned nod:1,	/* set 1 for no denormalised numbers */
-	__BITFIELD_FIELD(unsigned c:1,		/* condition */
-	__BITFIELD_FIELD(unsigned pad1:5,
+	__BITFIELD_FIELD(unsigned fcc:7,	/* condition[7:1] */
+	__BITFIELD_FIELD(unsigned nod:1,	/* set 1 for no denormals */
+	__BITFIELD_FIELD(unsigned c:1,		/* condition[0] */
+	__BITFIELD_FIELD(unsigned pad0:3,
+	__BITFIELD_FIELD(unsigned abs2008:1,	/* IEEE 754-2008 ABS/NEG.fmt */
+	__BITFIELD_FIELD(unsigned nan2008:1,	/* IEEE 754-2008 NaN mode */
 	__BITFIELD_FIELD(unsigned cx:6,		/* exceptions this operation */
 	__BITFIELD_FIELD(unsigned mx:5,		/* exception enable  mask */
 	__BITFIELD_FIELD(unsigned sx:5,		/* exceptions total */
 	__BITFIELD_FIELD(unsigned rm:2,		/* current rounding mode */
-	;))))))))
+	;))))))))))
 };
 #define ieee754_csr (*(struct _ieee754_csr *)(&current->thread.fpu.fcr31))