MIPS: Add MAC2008 Support

MAC2008 means the processor implemented IEEE754 style Fused MADD
instruction. It was introduced in Release3 but removed in Release5.

The toolchain support of MAC2008 have never landed except for Loongson
processors.

This patch aimed to disabled the MAC2008 if it's optional. For
MAC2008 only processors, we corrected math-emu behavior to align
with actual hardware behavior.

Signed-off-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
[paulburton@kernel.org: Fixup MIPSr2-r5 check in cpu_set_fpu_2008.]
Signed-off-by: Paul Burton <paulburton@kernel.org>
Cc: linux-mips@vger.kernel.org
Cc: chenhc@lemote.com
Cc: paul.burton@mips.com
Cc: linux-kernel@vger.kernel.org

diff --git a/arch/mips/include/asm/cpu-features.h b/arch/mips/include/asm/cpu-features.h
index 983a6a7f43a111a3d2de88a36e6747301f23b8c2..de44c92b1c1fece58f296bfaa3b6f2a736ae8690 100644 (file)
--- a/arch/mips/include/asm/cpu-features.h
+++ b/arch/mips/include/asm/cpu-features.h
@@ -555,6 +555,10 @@
 # define cpu_has_perf          __opt(MIPS_CPU_PERF)
 #endif
 
+#ifndef cpu_has_mac2008_only
+# define cpu_has_mac2008_only  __opt(MIPS_CPU_MAC_2008_ONLY)
+#endif
+
 #ifdef CONFIG_SMP
 /*
  * Some systems share FTLB RAMs between threads within a core (siblings in

diff --git a/arch/mips/include/asm/cpu.h b/arch/mips/include/asm/cpu.h
index 0e10ffcf0c1b40ccacfedc31c9040b5c946295ac..216a229167404bf5acb2e018a8b0ec51feab2e1b 100644 (file)
--- a/arch/mips/include/asm/cpu.h
+++ b/arch/mips/include/asm/cpu.h
@@ -416,6 +416,7 @@ enum cpu_type_enum {
 #define MIPS_CPU_MT_PER_TC_PERF_COUNTERS \
                                BIT_ULL(56)     /* CPU has perf counters implemented per TC (MIPSMT ASE) */
 #define MIPS_CPU_MMID          BIT_ULL(57)     /* CPU supports MemoryMapIDs */
+#define MIPS_CPU_MAC_2008_ONLY BIT_ULL(58)     /* CPU Only support MAC2008 Fused multiply-add instruction */
 
 /*
  * CPU ASE encodings

diff --git a/arch/mips/include/asm/mipsregs.h b/arch/mips/include/asm/mipsregs.h
index 0d5a3098869799bbce9021536532731cb0353645..796fe47cfd1737994923aecff019c0bfea09274a 100644 (file)
--- a/arch/mips/include/asm/mipsregs.h
+++ b/arch/mips/include/asm/mipsregs.h
@@ -1101,9 +1101,12 @@
 /*
  * Bits 22:20 of the FPU Status Register will be read as 0,
  * and should be written as zero.
+ * MAC2008 was removed in Release 5 so we still treat it as
+ * reserved.
  */
 #define FPU_CSR_RSVD   (_ULCAST_(7) << 20)
 
+#define FPU_CSR_MAC2008        (_ULCAST_(1) << 20)
 #define FPU_CSR_ABS2008        (_ULCAST_(1) << 19)
 #define FPU_CSR_NAN2008        (_ULCAST_(1) << 18)
 

diff --git a/arch/mips/kernel/cpu-probe.c b/arch/mips/kernel/cpu-probe.c
index c06365404a8e72172329218f2c3fad7738b29c7a..6ab6b03d35ba7c0b58a4027830aaa2d629f30dfb 100644 (file)
--- a/arch/mips/kernel/cpu-probe.c
+++ b/arch/mips/kernel/cpu-probe.c
@@ -102,7 +102,12 @@ static void cpu_set_fpu_2008(struct cpuinfo_mips *c)
                if (fir & MIPS_FPIR_HAS2008) {
                        fcsr = read_32bit_cp1_register(CP1_STATUS);
 
-                       fcsr0 = fcsr & ~(FPU_CSR_ABS2008 | FPU_CSR_NAN2008);
+                       /*
+                        * MAC2008 toolchain never landed in real world, so we're only
+                        * testing wether 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);
 
@@ -112,6 +117,15 @@ static void cpu_set_fpu_2008(struct cpuinfo_mips *c)
 
                        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)

diff --git a/arch/mips/math-emu/cp1emu.c b/arch/mips/math-emu/cp1emu.c
index 710e1f804a54bd0bdd03c67a85255b3efdfb73b8..9701c89e7e148fff4a6dd3f5c2ae93951baad547 100644 (file)
--- a/arch/mips/math-emu/cp1emu.c
+++ b/arch/mips/math-emu/cp1emu.c
@@ -1514,16 +1514,28 @@ static int fpux_emu(struct pt_regs *xcp, struct mips_fpu_struct *ctx,
                        break;
 
                case madd_s_op:
-                       handler = fpemu_sp_madd;
+                       if (cpu_has_mac2008_only)
+                               handler = ieee754sp_madd;
+                       else
+                               handler = fpemu_sp_madd;
                        goto scoptop;
                case msub_s_op:
-                       handler = fpemu_sp_msub;
+                       if (cpu_has_mac2008_only)
+                               handler = ieee754sp_msub;
+                       else
+                               handler = fpemu_sp_msub;
                        goto scoptop;
                case nmadd_s_op:
-                       handler = fpemu_sp_nmadd;
+                       if (cpu_has_mac2008_only)
+                               handler = ieee754sp_nmadd;
+                       else
+                               handler = fpemu_sp_nmadd;
                        goto scoptop;
                case nmsub_s_op:
-                       handler = fpemu_sp_nmsub;
+                       if (cpu_has_mac2008_only)
+                               handler = ieee754sp_nmsub;
+                       else
+                               handler = fpemu_sp_nmsub;
                        goto scoptop;
 
                      scoptop:
@@ -1610,15 +1622,27 @@ static int fpux_emu(struct pt_regs *xcp, struct mips_fpu_struct *ctx,
                        break;
 
                case madd_d_op:
-                       handler = fpemu_dp_madd;
+                       if (cpu_has_mac2008_only)
+                               handler = ieee754dp_madd;
+                       else
+                               handler = fpemu_dp_madd;
                        goto dcoptop;
                case msub_d_op:
-                       handler = fpemu_dp_msub;
+                       if (cpu_has_mac2008_only)
+                               handler = ieee754dp_msub;
+                       else
+                               handler = fpemu_dp_msub;
                        goto dcoptop;
                case nmadd_d_op:
-                       handler = fpemu_dp_nmadd;
+                       if (cpu_has_mac2008_only)
+                               handler = ieee754dp_nmadd;
+                       else
+                               handler = fpemu_dp_nmadd;
                        goto dcoptop;
                case nmsub_d_op:
+                       if (cpu_has_mac2008_only)
+                               handler = ieee754dp_nmsub;
+                       else
                        handler = fpemu_dp_nmsub;
                        goto dcoptop;
 

diff --git a/arch/mips/math-emu/dp_maddf.c b/arch/mips/math-emu/dp_maddf.c
index 3da0ce44cdef4fd4636e25673be1be5ab7172508..e24ef374d828e200e2ae84ad1fded29b399b7606 100644 (file)
--- a/arch/mips/math-emu/dp_maddf.c
+++ b/arch/mips/math-emu/dp_maddf.c
@@ -68,6 +68,12 @@ static union ieee754dp _dp_maddf(union ieee754dp z, union ieee754dp x,
 
        ieee754_clearcx();
 
+       rs = xs ^ ys;
+       if (flags & MADDF_NEGATE_PRODUCT)
+               rs ^= 1;
+       if (flags & MADDF_NEGATE_ADDITION)
+               zs ^= 1;
+
        /*
         * Handle the cases when at least one of x, y or z is a NaN.
         * Order of precedence is sNaN, qNaN and z, x, y.
@@ -104,9 +110,7 @@ static union ieee754dp _dp_maddf(union ieee754dp z, union ieee754dp x,
        case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_NORM):
        case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_DNORM):
        case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_INF):
-               if ((zc == IEEE754_CLASS_INF) &&
-                   ((!(flags & MADDF_NEGATE_PRODUCT) && (zs != (xs ^ ys))) ||
-                    ((flags & MADDF_NEGATE_PRODUCT) && (zs == (xs ^ ys))))) {
+               if ((zc == IEEE754_CLASS_INF) && (zs != rs)) {
                        /*
                         * Cases of addition of infinities with opposite signs
                         * or subtraction of infinities with same signs.
@@ -116,15 +120,10 @@ static union ieee754dp _dp_maddf(union ieee754dp z, union ieee754dp x,
                }
                /*
                 * z is here either not an infinity, or an infinity having the
-                * same sign as product (x*y) (in case of MADDF.D instruction)
-                * or product -(x*y) (in MSUBF.D case). The result must be an
-                * infinity, and its sign is determined only by the value of
-                * (flags & MADDF_NEGATE_PRODUCT) and the signs of x and y.
+                * same sign as product (x*y). The result must be an infinity,
+                * and its sign is determined only by the sign of product (x*y).
                 */
-               if (flags & MADDF_NEGATE_PRODUCT)
-                       return ieee754dp_inf(1 ^ (xs ^ ys));
-               else
-                       return ieee754dp_inf(xs ^ ys);
+               return ieee754dp_inf(rs);
 
        case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_ZERO):
        case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_NORM):
@@ -135,10 +134,7 @@ static union ieee754dp _dp_maddf(union ieee754dp z, union ieee754dp x,
                        return ieee754dp_inf(zs);
                if (zc == IEEE754_CLASS_ZERO) {
                        /* Handle cases +0 + (-0) and similar ones. */
-                       if ((!(flags & MADDF_NEGATE_PRODUCT)
-                                       && (zs == (xs ^ ys))) ||
-                           ((flags & MADDF_NEGATE_PRODUCT)
-                                       && (zs != (xs ^ ys))))
+                       if (zs == rs)
                                /*
                                 * Cases of addition of zeros of equal signs
                                 * or subtraction of zeroes of opposite signs.
@@ -187,9 +183,6 @@ static union ieee754dp _dp_maddf(union ieee754dp z, union ieee754dp x,
        assert(ym & DP_HIDDEN_BIT);
 
        re = xe + ye;
-       rs = xs ^ ys;
-       if (flags & MADDF_NEGATE_PRODUCT)
-               rs ^= 1;
 
        /* shunt to top of word */
        xm <<= 64 - (DP_FBITS + 1);
@@ -340,3 +333,27 @@ union ieee754dp ieee754dp_msubf(union ieee754dp z, union ieee754dp x,
 {
        return _dp_maddf(z, x, y, MADDF_NEGATE_PRODUCT);
 }
+
+union ieee754dp ieee754dp_madd(union ieee754dp z, union ieee754dp x,
+                               union ieee754dp y)
+{
+       return _dp_maddf(z, x, y, 0);
+}
+
+union ieee754dp ieee754dp_msub(union ieee754dp z, union ieee754dp x,
+                               union ieee754dp y)
+{
+       return _dp_maddf(z, x, y, MADDF_NEGATE_ADDITION);
+}
+
+union ieee754dp ieee754dp_nmadd(union ieee754dp z, union ieee754dp x,
+                               union ieee754dp y)
+{
+       return _dp_maddf(z, x, y, MADDF_NEGATE_PRODUCT|MADDF_NEGATE_ADDITION);
+}
+
+union ieee754dp ieee754dp_nmsub(union ieee754dp z, union ieee754dp x,
+                               union ieee754dp y)
+{
+       return _dp_maddf(z, x, y, MADDF_NEGATE_PRODUCT);
+}

diff --git a/arch/mips/math-emu/ieee754.h b/arch/mips/math-emu/ieee754.h
index b9167bd4eb60f622e06deca635f70412a7403b43..090caa740b1e31b8c0fe0bd0033fb91e977bf55a 100644 (file)
--- a/arch/mips/math-emu/ieee754.h
+++ b/arch/mips/math-emu/ieee754.h
@@ -68,6 +68,14 @@ union ieee754sp ieee754sp_maddf(union ieee754sp z, union ieee754sp x,
                                union ieee754sp y);
 union ieee754sp ieee754sp_msubf(union ieee754sp z, union ieee754sp x,
                                union ieee754sp y);
+union ieee754sp ieee754sp_madd(union ieee754sp z, union ieee754sp x,
+                               union ieee754sp y);
+union ieee754sp ieee754sp_msub(union ieee754sp z, union ieee754sp x,
+                               union ieee754sp y);
+union ieee754sp ieee754sp_nmadd(union ieee754sp z, union ieee754sp x,
+                               union ieee754sp y);
+union ieee754sp ieee754sp_nmsub(union ieee754sp z, union ieee754sp x,
+                               union ieee754sp y);
 int ieee754sp_2008class(union ieee754sp x);
 union ieee754sp ieee754sp_fmin(union ieee754sp x, union ieee754sp y);
 union ieee754sp ieee754sp_fmina(union ieee754sp x, union ieee754sp y);
@@ -103,6 +111,14 @@ union ieee754dp ieee754dp_maddf(union ieee754dp z, union ieee754dp x,
                                union ieee754dp y);
 union ieee754dp ieee754dp_msubf(union ieee754dp z, union ieee754dp x,
                                union ieee754dp y);
+union ieee754dp ieee754dp_madd(union ieee754dp z, union ieee754dp x,
+                               union ieee754dp y);
+union ieee754dp ieee754dp_msub(union ieee754dp z, union ieee754dp x,
+                               union ieee754dp y);
+union ieee754dp ieee754dp_nmadd(union ieee754dp z, union ieee754dp x,
+                               union ieee754dp y);
+union ieee754dp ieee754dp_nmsub(union ieee754dp z, union ieee754dp x,
+                               union ieee754dp y);
 int ieee754dp_2008class(union ieee754dp x);
 union ieee754dp ieee754dp_fmin(union ieee754dp x, union ieee754dp y);
 union ieee754dp ieee754dp_fmina(union ieee754dp x, union ieee754dp y);

diff --git a/arch/mips/math-emu/ieee754int.h b/arch/mips/math-emu/ieee754int.h
index 52b20119e315eebb4910ecafb0777a50333434c8..2c3b13546ac851a748d11135bf64aae4a12ebdde 100644 (file)
--- a/arch/mips/math-emu/ieee754int.h
+++ b/arch/mips/math-emu/ieee754int.h
@@ -16,6 +16,7 @@
 
 enum maddf_flags {
        MADDF_NEGATE_PRODUCT    = 1 << 0,
+       MADDF_NEGATE_ADDITION   = 1 << 1,
 };
 
 static inline void ieee754_clearcx(void)

diff --git a/arch/mips/math-emu/sp_maddf.c b/arch/mips/math-emu/sp_maddf.c
index d638354add6df5a6f9e4aa718be65b17071562af..1b85b1a527aca17013a4959d98245b23abd4f38a 100644 (file)
--- a/arch/mips/math-emu/sp_maddf.c
+++ b/arch/mips/math-emu/sp_maddf.c
@@ -36,6 +36,12 @@ static union ieee754sp _sp_maddf(union ieee754sp z, union ieee754sp x,
 
        ieee754_clearcx();
 
+       rs = xs ^ ys;
+       if (flags & MADDF_NEGATE_PRODUCT)
+               rs ^= 1;
+       if (flags & MADDF_NEGATE_ADDITION)
+               zs ^= 1;
+
        /*
         * Handle the cases when at least one of x, y or z is a NaN.
         * Order of precedence is sNaN, qNaN and z, x, y.
@@ -73,9 +79,7 @@ static union ieee754sp _sp_maddf(union ieee754sp z, union ieee754sp x,
        case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_NORM):
        case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_DNORM):
        case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_INF):
-               if ((zc == IEEE754_CLASS_INF) &&
-                   ((!(flags & MADDF_NEGATE_PRODUCT) && (zs != (xs ^ ys))) ||
-                    ((flags & MADDF_NEGATE_PRODUCT) && (zs == (xs ^ ys))))) {
+               if ((zc == IEEE754_CLASS_INF) && (zs != rs)) {
                        /*
                         * Cases of addition of infinities with opposite signs
                         * or subtraction of infinities with same signs.
@@ -85,15 +89,10 @@ static union ieee754sp _sp_maddf(union ieee754sp z, union ieee754sp x,
                }
                /*
                 * z is here either not an infinity, or an infinity having the
-                * same sign as product (x*y) (in case of MADDF.D instruction)
-                * or product -(x*y) (in MSUBF.D case). The result must be an
-                * infinity, and its sign is determined only by the value of
-                * (flags & MADDF_NEGATE_PRODUCT) and the signs of x and y.
+                * same sign as product (x*y). The result must be an infinity,
+                * and its sign is determined only by the sign of product (x*y).
                 */
-               if (flags & MADDF_NEGATE_PRODUCT)
-                       return ieee754sp_inf(1 ^ (xs ^ ys));
-               else
-                       return ieee754sp_inf(xs ^ ys);
+               return ieee754sp_inf(rs);
 
        case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_ZERO):
        case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_NORM):
@@ -104,10 +103,7 @@ static union ieee754sp _sp_maddf(union ieee754sp z, union ieee754sp x,
                        return ieee754sp_inf(zs);
                if (zc == IEEE754_CLASS_ZERO) {
                        /* Handle cases +0 + (-0) and similar ones. */
-                       if ((!(flags & MADDF_NEGATE_PRODUCT)
-                                       && (zs == (xs ^ ys))) ||
-                           ((flags & MADDF_NEGATE_PRODUCT)
-                                       && (zs != (xs ^ ys))))
+                       if (zs == rs)
                                /*
                                 * Cases of addition of zeros of equal signs
                                 * or subtraction of zeroes of opposite signs.
@@ -158,9 +154,6 @@ static union ieee754sp _sp_maddf(union ieee754sp z, union ieee754sp x,
        assert(ym & SP_HIDDEN_BIT);
 
        re = xe + ye;
-       rs = xs ^ ys;
-       if (flags & MADDF_NEGATE_PRODUCT)
-               rs ^= 1;
 
        /* Multiple 24 bit xm and ym to give 48 bit results */
        rm64 = (uint64_t)xm * ym;
@@ -260,3 +253,27 @@ union ieee754sp ieee754sp_msubf(union ieee754sp z, union ieee754sp x,
 {
        return _sp_maddf(z, x, y, MADDF_NEGATE_PRODUCT);
 }
+
+union ieee754sp ieee754sp_madd(union ieee754sp z, union ieee754sp x,
+                               union ieee754sp y)
+{
+       return _sp_maddf(z, x, y, 0);
+}
+
+union ieee754sp ieee754sp_msub(union ieee754sp z, union ieee754sp x,
+                               union ieee754sp y)
+{
+       return _sp_maddf(z, x, y, MADDF_NEGATE_ADDITION);
+}
+
+union ieee754sp ieee754sp_nmadd(union ieee754sp z, union ieee754sp x,
+                               union ieee754sp y)
+{
+       return _sp_maddf(z, x, y, MADDF_NEGATE_PRODUCT|MADDF_NEGATE_ADDITION);
+}
+
+union ieee754sp ieee754sp_nmsub(union ieee754sp z, union ieee754sp x,
+                               union ieee754sp y)
+{
+       return _sp_maddf(z, x, y, MADDF_NEGATE_PRODUCT);
+}