sh: SH-2A FPU support.

Signed-off-by: Kieran Bingham <kbingham@mpc-data.co.uk>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>

2 files changed, 635 insertions, 0 deletions

diff --git a/arch/sh/kernel/cpu/sh2a/Makefile b/arch/sh/kernel/cpu/sh2a/Makefile
index 50e4d0ffdd6f..b279cdc3a233 100644
--- a/arch/sh/kernel/cpu/sh2a/Makefile
+++ b/arch/sh/kernel/cpu/sh2a/Makefile
@@ -6,6 +6,8 @@ obj-y	:= common.o probe.o opcode_helper.o
 
 common-y	+= $(addprefix ../sh2/, ex.o entry.o)
 
+obj-$(CONFIG_SH_FPU)	+= fpu.o
+
 obj-$(CONFIG_CPU_SUBTYPE_SH7206) += setup-sh7206.o clock-sh7206.o
 obj-$(CONFIG_CPU_SUBTYPE_SH7203) += setup-sh7203.o clock-sh7203.o
 obj-$(CONFIG_CPU_SUBTYPE_SH7263) += setup-sh7203.o clock-sh7203.o
diff --git a/arch/sh/kernel/cpu/sh2a/fpu.c b/arch/sh/kernel/cpu/sh2a/fpu.c
new file mode 100644
index 000000000000..ff99562456fb
--- /dev/null
+++ b/arch/sh/kernel/cpu/sh2a/fpu.c
@@ -0,0 +1,633 @@
+/*
+ * Save/restore floating point context for signal handlers.
+ *
+ * Copyright (C) 1999, 2000  Kaz Kojima & Niibe Yutaka
+ *
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License.  See the file "COPYING" in the main directory of this archive
+ * for more details.
+ *
+ * FIXME! These routines can be optimized in big endian case.
+ */
+#include <linux/sched.h>
+#include <linux/signal.h>
+#include <asm/processor.h>
+#include <asm/io.h>
+
+/* The PR (precision) bit in the FP Status Register must be clear when
+ * an frchg instruction is executed, otherwise the instruction is undefined.
+ * Executing frchg with PR set causes a trap on some SH4 implementations.
+ */
+
+#define FPSCR_RCHG 0x00000000
+
+
+/*
+ * Save FPU registers onto task structure.
+ * Assume called with FPU enabled (SR.FD=0).
+ */
+void
+save_fpu(struct task_struct *tsk, struct pt_regs *regs)
+{
+	unsigned long dummy;
+
+	clear_tsk_thread_flag(tsk, TIF_USEDFPU);
+	enable_fpu();
+	asm volatile("sts.l	fpul, @-%0\n\t"
+		     "sts.l	fpscr, @-%0\n\t"
+		     "fmov.s	fr15, @-%0\n\t"
+		     "fmov.s	fr14, @-%0\n\t"
+		     "fmov.s	fr13, @-%0\n\t"
+		     "fmov.s	fr12, @-%0\n\t"
+		     "fmov.s	fr11, @-%0\n\t"
+		     "fmov.s	fr10, @-%0\n\t"
+		     "fmov.s	fr9, @-%0\n\t"
+		     "fmov.s	fr8, @-%0\n\t"
+		     "fmov.s	fr7, @-%0\n\t"
+		     "fmov.s	fr6, @-%0\n\t"
+		     "fmov.s	fr5, @-%0\n\t"
+		     "fmov.s	fr4, @-%0\n\t"
+		     "fmov.s	fr3, @-%0\n\t"
+		     "fmov.s	fr2, @-%0\n\t"
+		     "fmov.s	fr1, @-%0\n\t"
+		     "fmov.s	fr0, @-%0\n\t"
+		     "lds	%3, fpscr\n\t"
+		     : "=r" (dummy)
+		     : "0" ((char *)(&tsk->thread.fpu.hard.status)),
+		       "r" (FPSCR_RCHG),
+		       "r" (FPSCR_INIT)
+		     : "memory");
+
+	disable_fpu();
+	release_fpu(regs);
+}
+
+static void
+restore_fpu(struct task_struct *tsk)
+{
+	unsigned long dummy;
+
+	enable_fpu();
+	asm volatile("fmov.s	@%0+, fr0\n\t"
+		     "fmov.s	@%0+, fr1\n\t"
+		     "fmov.s	@%0+, fr2\n\t"
+		     "fmov.s	@%0+, fr3\n\t"
+		     "fmov.s	@%0+, fr4\n\t"
+		     "fmov.s	@%0+, fr5\n\t"
+		     "fmov.s	@%0+, fr6\n\t"
+		     "fmov.s	@%0+, fr7\n\t"
+		     "fmov.s	@%0+, fr8\n\t"
+		     "fmov.s	@%0+, fr9\n\t"
+		     "fmov.s	@%0+, fr10\n\t"
+		     "fmov.s	@%0+, fr11\n\t"
+		     "fmov.s	@%0+, fr12\n\t"
+		     "fmov.s	@%0+, fr13\n\t"
+		     "fmov.s	@%0+, fr14\n\t"
+		     "fmov.s	@%0+, fr15\n\t"
+		     "lds.l	@%0+, fpscr\n\t"
+		     "lds.l	@%0+, fpul\n\t"
+		     : "=r" (dummy)
+		     : "0" (&tsk->thread.fpu), "r" (FPSCR_RCHG)
+		     : "memory");
+	disable_fpu();
+}
+
+/*
+ * Load the FPU with signalling NANS.  This bit pattern we're using
+ * has the property that no matter wether considered as single or as
+ * double precission represents signaling NANS.
+ */
+
+static void
+fpu_init(void)
+{
+	enable_fpu();
+	asm volatile("lds	%0, fpul\n\t"
+		     "fsts	fpul, fr0\n\t"
+		     "fsts	fpul, fr1\n\t"
+		     "fsts	fpul, fr2\n\t"
+		     "fsts	fpul, fr3\n\t"
+		     "fsts	fpul, fr4\n\t"
+		     "fsts	fpul, fr5\n\t"
+		     "fsts	fpul, fr6\n\t"
+		     "fsts	fpul, fr7\n\t"
+		     "fsts	fpul, fr8\n\t"
+		     "fsts	fpul, fr9\n\t"
+		     "fsts	fpul, fr10\n\t"
+		     "fsts	fpul, fr11\n\t"
+		     "fsts	fpul, fr12\n\t"
+		     "fsts	fpul, fr13\n\t"
+		     "fsts	fpul, fr14\n\t"
+		     "fsts	fpul, fr15\n\t"
+		     "lds	%2, fpscr\n\t"
+		     : /* no output */
+		     : "r" (0), "r" (FPSCR_RCHG), "r" (FPSCR_INIT));
+	disable_fpu();
+}
+
+/*
+ *	Emulate arithmetic ops on denormalized number for some FPU insns.
+ */
+
+/* denormalized float * float */
+static int denormal_mulf(int hx, int hy)
+{
+	unsigned int ix, iy;
+	unsigned long long m, n;
+	int exp, w;
+
+	ix = hx & 0x7fffffff;
+	iy = hy & 0x7fffffff;
+	if (iy < 0x00800000 || ix == 0)
+		return ((hx ^ hy) & 0x80000000);
+
+	exp = (iy & 0x7f800000) >> 23;
+	ix &= 0x007fffff;
+	iy = (iy & 0x007fffff) | 0x00800000;
+	m = (unsigned long long)ix * iy;
+	n = m;
+	w = -1;
+	while (n) { n >>= 1; w++; }
+
+	/* FIXME: use guard bits */
+	exp += w - 126 - 46;
+	if (exp > 0)
+		ix = ((int) (m >> (w - 23)) & 0x007fffff) | (exp << 23);
+	else if (exp + 22 >= 0)
+		ix = (int) (m >> (w - 22 - exp)) & 0x007fffff;
+	else
+		ix = 0;
+
+	ix |= (hx ^ hy) & 0x80000000;
+	return ix;
+}
+
+/* denormalized double * double */
+static void mult64(unsigned long long x, unsigned long long y,
+		unsigned long long *highp, unsigned long long *lowp)
+{
+	unsigned long long sub0, sub1, sub2, sub3;
+	unsigned long long high, low;
+
+	sub0 = (x >> 32) * (unsigned long) (y >> 32);
+	sub1 = (x & 0xffffffffLL) * (unsigned long) (y >> 32);
+	sub2 = (x >> 32) * (unsigned long) (y & 0xffffffffLL);
+	sub3 = (x & 0xffffffffLL) * (unsigned long) (y & 0xffffffffLL);
+	low = sub3;
+	high = 0LL;
+	sub3 += (sub1 << 32);
+	if (low > sub3)
+		high++;
+	low = sub3;
+	sub3 += (sub2 << 32);
+	if (low > sub3)
+		high++;
+	low = sub3;
+	high += (sub1 >> 32) + (sub2 >> 32);
+	high += sub0;
+	*lowp = low;
+	*highp = high;
+}
+
+static inline long long rshift64(unsigned long long mh,
+		unsigned long long ml, int n)
+{
+	if (n >= 64)
+		return mh >> (n - 64);
+	return (mh << (64 - n)) | (ml >> n);
+}
+
+static long long denormal_muld(long long hx, long long hy)
+{
+	unsigned long long ix, iy;
+	unsigned long long mh, ml, nh, nl;
+	int exp, w;
+
+	ix = hx & 0x7fffffffffffffffLL;
+	iy = hy & 0x7fffffffffffffffLL;
+	if (iy < 0x0010000000000000LL || ix == 0)
+		return ((hx ^ hy) & 0x8000000000000000LL);
+
+	exp = (iy & 0x7ff0000000000000LL) >> 52;
+	ix &= 0x000fffffffffffffLL;
+	iy = (iy & 0x000fffffffffffffLL) | 0x0010000000000000LL;
+	mult64(ix, iy, &mh, &ml);
+	nh = mh;
+	nl = ml;
+	w = -1;
+	if (nh) {
+		while (nh) { nh >>= 1; w++;}
+		w += 64;
+	} else
+		while (nl) { nl >>= 1; w++;}
+
+	/* FIXME: use guard bits */
+	exp += w - 1022 - 52 * 2;
+	if (exp > 0)
+		ix = (rshift64(mh, ml, w - 52) & 0x000fffffffffffffLL)
+			| ((long long)exp << 52);
+	else if (exp + 51 >= 0)
+		ix = rshift64(mh, ml, w - 51 - exp) & 0x000fffffffffffffLL;
+	else
+		ix = 0;
+
+	ix |= (hx ^ hy) & 0x8000000000000000LL;
+	return ix;
+}
+
+/* ix - iy where iy: denormal and ix, iy >= 0 */
+static int denormal_subf1(unsigned int ix, unsigned int iy)
+{
+	int frac;
+	int exp;
+
+	if (ix < 0x00800000)
+		return ix - iy;
+
+	exp = (ix & 0x7f800000) >> 23;
+	if (exp - 1 > 31)
+		return ix;
+	iy >>= exp - 1;
+	if (iy == 0)
+		return ix;
+
+	frac = (ix & 0x007fffff) | 0x00800000;
+	frac -= iy;
+	while (frac < 0x00800000) {
+		if (--exp == 0)
+			return frac;
+		frac <<= 1;
+	}
+
+	return (exp << 23) | (frac & 0x007fffff);
+}
+
+/* ix + iy where iy: denormal and ix, iy >= 0 */
+static int denormal_addf1(unsigned int ix, unsigned int iy)
+{
+	int frac;
+	int exp;
+
+	if (ix < 0x00800000)
+		return ix + iy;
+
+	exp = (ix & 0x7f800000) >> 23;
+	if (exp - 1 > 31)
+		return ix;
+	iy >>= exp - 1;
+	if (iy == 0)
+	  return ix;
+
+	frac = (ix & 0x007fffff) | 0x00800000;
+	frac += iy;
+	if (frac >= 0x01000000) {
+		frac >>= 1;
+		++exp;
+	}
+
+	return (exp << 23) | (frac & 0x007fffff);
+}
+
+static int denormal_addf(int hx, int hy)
+{
+	unsigned int ix, iy;
+	int sign;
+
+	if ((hx ^ hy) & 0x80000000) {
+		sign = hx & 0x80000000;
+		ix = hx & 0x7fffffff;
+		iy = hy & 0x7fffffff;
+		if (iy < 0x00800000) {
+			ix = denormal_subf1(ix, iy);
+			if (ix < 0) {
+				ix = -ix;
+				sign ^= 0x80000000;
+			}
+		} else {
+			ix = denormal_subf1(iy, ix);
+			sign ^= 0x80000000;
+		}
+	} else {
+		sign = hx & 0x80000000;
+		ix = hx & 0x7fffffff;
+		iy = hy & 0x7fffffff;
+		if (iy < 0x00800000)
+			ix = denormal_addf1(ix, iy);
+		else
+			ix = denormal_addf1(iy, ix);
+	}
+
+	return sign | ix;
+}
+
+/* ix - iy where iy: denormal and ix, iy >= 0 */
+static long long denormal_subd1(unsigned long long ix, unsigned long long iy)
+{
+	long long frac;
+	int exp;
+
+	if (ix < 0x0010000000000000LL)
+		return ix - iy;
+
+	exp = (ix & 0x7ff0000000000000LL) >> 52;
+	if (exp - 1 > 63)
+		return ix;
+	iy >>= exp - 1;
+	if (iy == 0)
+		return ix;
+
+	frac = (ix & 0x000fffffffffffffLL) | 0x0010000000000000LL;
+	frac -= iy;
+	while (frac < 0x0010000000000000LL) {
+		if (--exp == 0)
+			return frac;
+		frac <<= 1;
+	}
+
+	return ((long long)exp << 52) | (frac & 0x000fffffffffffffLL);
+}
+
+/* ix + iy where iy: denormal and ix, iy >= 0 */
+static long long denormal_addd1(unsigned long long ix, unsigned long long iy)
+{
+	long long frac;
+	long long exp;
+
+	if (ix < 0x0010000000000000LL)
+		return ix + iy;
+
+	exp = (ix & 0x7ff0000000000000LL) >> 52;
+	if (exp - 1 > 63)
+		return ix;
+	iy >>= exp - 1;
+	if (iy == 0)
+	  return ix;
+
+	frac = (ix & 0x000fffffffffffffLL) | 0x0010000000000000LL;
+	frac += iy;
+	if (frac >= 0x0020000000000000LL) {
+		frac >>= 1;
+		++exp;
+	}
+
+	return (exp << 52) | (frac & 0x000fffffffffffffLL);
+}
+
+static long long denormal_addd(long long hx, long long hy)
+{
+	unsigned long long ix, iy;
+	long long sign;
+
+	if ((hx ^ hy) & 0x8000000000000000LL) {
+		sign = hx & 0x8000000000000000LL;
+		ix = hx & 0x7fffffffffffffffLL;
+		iy = hy & 0x7fffffffffffffffLL;
+		if (iy < 0x0010000000000000LL) {
+			ix = denormal_subd1(ix, iy);
+			if (ix < 0) {
+				ix = -ix;
+				sign ^= 0x8000000000000000LL;
+			}
+		} else {
+			ix = denormal_subd1(iy, ix);
+			sign ^= 0x8000000000000000LL;
+		}
+	} else {
+		sign = hx & 0x8000000000000000LL;
+		ix = hx & 0x7fffffffffffffffLL;
+		iy = hy & 0x7fffffffffffffffLL;
+		if (iy < 0x0010000000000000LL)
+			ix = denormal_addd1(ix, iy);
+		else
+			ix = denormal_addd1(iy, ix);
+	}
+
+	return sign | ix;
+}
+
+/**
+ *	denormal_to_double - Given denormalized float number,
+ *	                     store double float
+ *
+ *	@fpu: Pointer to sh_fpu_hard structure
+ *	@n: Index to FP register
+ */
+static void
+denormal_to_double (struct sh_fpu_hard_struct *fpu, int n)
+{
+	unsigned long du, dl;
+	unsigned long x = fpu->fpul;
+	int exp = 1023 - 126;
+
+	if (x != 0 && (x & 0x7f800000) == 0) {
+		du = (x & 0x80000000);
+		while ((x & 0x00800000) == 0) {
+			x <<= 1;
+			exp--;
+		}
+		x &= 0x007fffff;
+		du |= (exp << 20) | (x >> 3);
+		dl = x << 29;
+
+		fpu->fp_regs[n] = du;
+		fpu->fp_regs[n+1] = dl;
+	}
+}
+
+/**
+ *	ieee_fpe_handler - Handle denormalized number exception
+ *
+ *	@regs: Pointer to register structure
+ *
+ *	Returns 1 when it's handled (should not cause exception).
+ */
+static int
+ieee_fpe_handler (struct pt_regs *regs)
+{
+	unsigned short insn = *(unsigned short *) regs->pc;
+	unsigned short finsn;
+	unsigned long nextpc;
+	int nib[4] = {
+		(insn >> 12) & 0xf,
+		(insn >> 8) & 0xf,
+		(insn >> 4) & 0xf,
+		insn & 0xf};
+
+	if (nib[0] == 0xb ||
+	    (nib[0] == 0x4 && nib[2] == 0x0 && nib[3] == 0xb)) /* bsr & jsr */
+		regs->pr = regs->pc + 4;
+	if (nib[0] == 0xa || nib[0] == 0xb) { /* bra & bsr */
+		nextpc = regs->pc + 4 + ((short) ((insn & 0xfff) << 4) >> 3);
+		finsn = *(unsigned short *) (regs->pc + 2);
+	} else if (nib[0] == 0x8 && nib[1] == 0xd) { /* bt/s */
+		if (regs->sr & 1)
+			nextpc = regs->pc + 4 + ((char) (insn & 0xff) << 1);
+		else
+			nextpc = regs->pc + 4;
+		finsn = *(unsigned short *) (regs->pc + 2);
+	} else if (nib[0] == 0x8 && nib[1] == 0xf) { /* bf/s */
+		if (regs->sr & 1)
+			nextpc = regs->pc + 4;
+		else
+			nextpc = regs->pc + 4 + ((char) (insn & 0xff) << 1);
+		finsn = *(unsigned short *) (regs->pc + 2);
+	} else if (nib[0] == 0x4 && nib[3] == 0xb &&
+		 (nib[2] == 0x0 || nib[2] == 0x2)) { /* jmp & jsr */
+		nextpc = regs->regs[nib[1]];
+		finsn = *(unsigned short *) (regs->pc + 2);
+	} else if (nib[0] == 0x0 && nib[3] == 0x3 &&
+		 (nib[2] == 0x0 || nib[2] == 0x2)) { /* braf & bsrf */
+		nextpc = regs->pc + 4 + regs->regs[nib[1]];
+		finsn = *(unsigned short *) (regs->pc + 2);
+	} else if (insn == 0x000b) { /* rts */
+		nextpc = regs->pr;
+		finsn = *(unsigned short *) (regs->pc + 2);
+	} else {
+		nextpc = regs->pc + 2;
+		finsn = insn;
+	}
+
+#define FPSCR_FPU_ERROR (1 << 17)
+
+	if ((finsn & 0xf1ff) == 0xf0ad) { /* fcnvsd */
+		struct task_struct *tsk = current;
+
+		if ((tsk->thread.fpu.hard.fpscr & FPSCR_FPU_ERROR)) {
+			/* FPU error */
+			denormal_to_double (&tsk->thread.fpu.hard,
+					    (finsn >> 8) & 0xf);
+		} else
+			return 0;
+
+		regs->pc = nextpc;
+		return 1;
+	} else if ((finsn & 0xf00f) == 0xf002) { /* fmul */
+		struct task_struct *tsk = current;
+		int fpscr;
+		int n, m, prec;
+		unsigned int hx, hy;
+
+		n = (finsn >> 8) & 0xf;
+		m = (finsn >> 4) & 0xf;
+		hx = tsk->thread.fpu.hard.fp_regs[n];
+		hy = tsk->thread.fpu.hard.fp_regs[m];
+		fpscr = tsk->thread.fpu.hard.fpscr;
+		prec = fpscr & (1 << 19);
+
+		if ((fpscr & FPSCR_FPU_ERROR)
+		     && (prec && ((hx & 0x7fffffff) < 0x00100000
+				   || (hy & 0x7fffffff) < 0x00100000))) {
+			long long llx, lly;
+
+			/* FPU error because of denormal */
+			llx = ((long long) hx << 32)
+			       | tsk->thread.fpu.hard.fp_regs[n+1];
+			lly = ((long long) hy << 32)
+			       | tsk->thread.fpu.hard.fp_regs[m+1];
+			if ((hx & 0x7fffffff) >= 0x00100000)
+				llx = denormal_muld(lly, llx);
+			else
+				llx = denormal_muld(llx, lly);
+			tsk->thread.fpu.hard.fp_regs[n] = llx >> 32;
+			tsk->thread.fpu.hard.fp_regs[n+1] = llx & 0xffffffff;
+		} else if ((fpscr & FPSCR_FPU_ERROR)
+		     && (!prec && ((hx & 0x7fffffff) < 0x00800000
+				   || (hy & 0x7fffffff) < 0x00800000))) {
+			/* FPU error because of denormal */
+			if ((hx & 0x7fffffff) >= 0x00800000)
+				hx = denormal_mulf(hy, hx);
+			else
+				hx = denormal_mulf(hx, hy);
+			tsk->thread.fpu.hard.fp_regs[n] = hx;
+		} else
+			return 0;
+
+		regs->pc = nextpc;
+		return 1;
+	} else if ((finsn & 0xf00e) == 0xf000) { /* fadd, fsub */
+		struct task_struct *tsk = current;
+		int fpscr;
+		int n, m, prec;
+		unsigned int hx, hy;
+
+		n = (finsn >> 8) & 0xf;
+		m = (finsn >> 4) & 0xf;
+		hx = tsk->thread.fpu.hard.fp_regs[n];
+		hy = tsk->thread.fpu.hard.fp_regs[m];
+		fpscr = tsk->thread.fpu.hard.fpscr;
+		prec = fpscr & (1 << 19);
+
+		if ((fpscr & FPSCR_FPU_ERROR)
+		     && (prec && ((hx & 0x7fffffff) < 0x00100000
+				   || (hy & 0x7fffffff) < 0x00100000))) {
+			long long llx, lly;
+
+			/* FPU error because of denormal */
+			llx = ((long long) hx << 32)
+			       | tsk->thread.fpu.hard.fp_regs[n+1];
+			lly = ((long long) hy << 32)
+			       | tsk->thread.fpu.hard.fp_regs[m+1];
+			if ((finsn & 0xf00f) == 0xf000)
+				llx = denormal_addd(llx, lly);
+			else
+				llx = denormal_addd(llx, lly ^ (1LL << 63));
+			tsk->thread.fpu.hard.fp_regs[n] = llx >> 32;
+			tsk->thread.fpu.hard.fp_regs[n+1] = llx & 0xffffffff;
+		} else if ((fpscr & FPSCR_FPU_ERROR)
+		     && (!prec && ((hx & 0x7fffffff) < 0x00800000
+				   || (hy & 0x7fffffff) < 0x00800000))) {
+			/* FPU error because of denormal */
+			if ((finsn & 0xf00f) == 0xf000)
+				hx = denormal_addf(hx, hy);
+			else
+				hx = denormal_addf(hx, hy ^ 0x80000000);
+			tsk->thread.fpu.hard.fp_regs[n] = hx;
+		} else
+			return 0;
+
+		regs->pc = nextpc;
+		return 1;
+	}
+
+	return 0;
+}
+
+BUILD_TRAP_HANDLER(fpu_error)
+{
+	struct task_struct *tsk = current;
+	TRAP_HANDLER_DECL;
+
+	save_fpu(tsk, regs);
+	if (ieee_fpe_handler(regs)) {
+		tsk->thread.fpu.hard.fpscr &=
+			~(FPSCR_CAUSE_MASK | FPSCR_FLAG_MASK);
+		grab_fpu(regs);
+		restore_fpu(tsk);
+		set_tsk_thread_flag(tsk, TIF_USEDFPU);
+		return;
+	}
+
+	force_sig(SIGFPE, tsk);
+}
+
+BUILD_TRAP_HANDLER(fpu_state_restore)
+{
+	struct task_struct *tsk = current;
+	TRAP_HANDLER_DECL;
+
+	grab_fpu(regs);
+	if (!user_mode(regs)) {
+		printk(KERN_ERR "BUG: FPU is used in kernel mode.\n");
+		return;
+	}
+
+	if (used_math()) {
+		/* Using the FPU again.  */
+		restore_fpu(tsk);
+	} else	{
+		/* First time FPU user.  */
+		fpu_init();
+		set_used_math();
+	}
+	set_tsk_thread_flag(tsk, TIF_USEDFPU);
+}