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authorStephen Chivers <schivers@csc.com>2014-02-21 12:29:48 +1100
committerBenjamin Herrenschmidt <benh@kernel.crashing.org>2014-04-07 10:33:11 +1000
commitc59c015b6aa5bc18d01c8e482149086cafd7332a (patch)
treef6fd1b1aa1f52fd43b326ef3078375b15177f1a8 /arch/powerpc/math-emu
parent18a1a7a1d862ae0794a0179473d08a414dd49234 (diff)
downloadlinux-c59c015b6aa5bc18d01c8e482149086cafd7332a.tar.bz2
powerpc: Correct emulated mtfsf instruction
The emulated (CONFIG_MATH_EMULATION_FULL) PowerPC Floating Point instruction mtfsf does not correctly copy bits from its source register to the Floating Point Status and Register (FPSCR). The error is in the preparation of the mask used to select the bits to be copied from the source to the FPSCR. Execution of the mtfsf instruction does not produce the same results on a MPC8548 platform (emulated floating point) as on MPC7410 or 440EP platforms (hardware floating point). This error has been detected using a Freescale MPC8548 based platform and the patch below tested using that platform. The patch is based on the patch(es) provided by Gabriel Paubert and analysis by Gabriel, James Yang and David Laight. Signed-off-by: Stephen Chivers <schivers@csc.com> Signed-off-by: Gabriel Paubert <paubert@iram.es> Tested-by: Stephen Chivers <schivers@csc.com> Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Diffstat (limited to 'arch/powerpc/math-emu')
-rw-r--r--arch/powerpc/math-emu/mtfsf.c58
1 files changed, 23 insertions, 35 deletions
diff --git a/arch/powerpc/math-emu/mtfsf.c b/arch/powerpc/math-emu/mtfsf.c
index dbce92e4f046..44b0fc8214f4 100644
--- a/arch/powerpc/math-emu/mtfsf.c
+++ b/arch/powerpc/math-emu/mtfsf.c
@@ -11,48 +11,36 @@ mtfsf(unsigned int FM, u32 *frB)
u32 mask;
u32 fpscr;
- if (FM == 0)
- return 0;
-
- if (FM == 0xff)
- mask = 0x9fffffff;
+ if (likely(FM == 1))
+ mask = 0x0f;
+ else if (likely(FM == 0xff))
+ mask = ~0;
else {
- mask = 0;
- if (FM & (1 << 0))
- mask |= 0x90000000;
- if (FM & (1 << 1))
- mask |= 0x0f000000;
- if (FM & (1 << 2))
- mask |= 0x00f00000;
- if (FM & (1 << 3))
- mask |= 0x000f0000;
- if (FM & (1 << 4))
- mask |= 0x0000f000;
- if (FM & (1 << 5))
- mask |= 0x00000f00;
- if (FM & (1 << 6))
- mask |= 0x000000f0;
- if (FM & (1 << 7))
- mask |= 0x0000000f;
+ mask = ((FM & 1) |
+ ((FM << 3) & 0x10) |
+ ((FM << 6) & 0x100) |
+ ((FM << 9) & 0x1000) |
+ ((FM << 12) & 0x10000) |
+ ((FM << 15) & 0x100000) |
+ ((FM << 18) & 0x1000000) |
+ ((FM << 21) & 0x10000000)) * 15;
}
- __FPU_FPSCR &= ~(mask);
- __FPU_FPSCR |= (frB[1] & mask);
+ fpscr = ((__FPU_FPSCR & ~mask) | (frB[1] & mask)) &
+ ~(FPSCR_VX | FPSCR_FEX | 0x800);
- __FPU_FPSCR &= ~(FPSCR_VX);
- if (__FPU_FPSCR & (FPSCR_VXSNAN | FPSCR_VXISI | FPSCR_VXIDI |
+ if (fpscr & (FPSCR_VXSNAN | FPSCR_VXISI | FPSCR_VXIDI |
FPSCR_VXZDZ | FPSCR_VXIMZ | FPSCR_VXVC |
FPSCR_VXSOFT | FPSCR_VXSQRT | FPSCR_VXCVI))
- __FPU_FPSCR |= FPSCR_VX;
-
- fpscr = __FPU_FPSCR;
- fpscr &= ~(FPSCR_FEX);
- if (((fpscr & FPSCR_VX) && (fpscr & FPSCR_VE)) ||
- ((fpscr & FPSCR_OX) && (fpscr & FPSCR_OE)) ||
- ((fpscr & FPSCR_UX) && (fpscr & FPSCR_UE)) ||
- ((fpscr & FPSCR_ZX) && (fpscr & FPSCR_ZE)) ||
- ((fpscr & FPSCR_XX) && (fpscr & FPSCR_XE)))
+ fpscr |= FPSCR_VX;
+
+ /* The bit order of exception enables and exception status
+ * is the same. Simply shift and mask to check for enabled
+ * exceptions.
+ */
+ if (fpscr & (fpscr >> 22) & 0xf8)
fpscr |= FPSCR_FEX;
+
__FPU_FPSCR = fpscr;
#ifdef DEBUG