diff options
| author | Paul Burton <paul.burton@imgtec.com> | 2013-11-22 13:12:07 +0000 |
|---|---|---|
| committer | Ralf Baechle <ralf@linux-mips.org> | 2014-01-13 23:40:56 +0100 |
| commit | 597ce1723e0fa0bdbe2ae4c94f18da6e29b92635 (patch) | |
| tree | 21f67268915b8457dd305c6bcf7ac905772fd0ee /arch/mips/kernel/r4k_switch.S | |
| parent | 56a22d21bf9744315f56b2bbd6416170f27b7765 (diff) | |
MIPS: Support for 64-bit FP with O32 binaries
CPUs implementing MIPS32 R2 may include a 64-bit FPU, just as MIPS64 CPUs
do. In order to preserve backwards compatibility a 64-bit FPU will act
like a 32-bit FPU (by accessing doubles from the least significant 32
bits of an even-odd pair of FP registers) when the Status.FR bit is
zero, again just like a mips64 CPU. The standard O32 ABI is defined
expecting a 32-bit FPU, however recent toolchains support use of a
64-bit FPU from an O32 MIPS32 executable. When an ELF executable is
built to use a 64-bit FPU a new flag (EF_MIPS_FP64) is set in the ELF
header.
With this patch the kernel will check the EF_MIPS_FP64 flag when
executing an O32 binary, and set Status.FR accordingly. The addition
of O32 64-bit FP support lessens the opportunity for optimisation in
the FPU emulator, so a CONFIG_MIPS_O32_FP64_SUPPORT Kconfig option is
introduced to allow this support to be disabled for those that don't
require it.
Inspired by an earlier patch by Leonid Yegoshin, but implemented more
cleanly & correctly.
Signed-off-by: Paul Burton <paul.burton@imgtec.com>
Cc: linux-mips@linux-mips.org
Cc: Paul Burton <paul.burton@imgtec.com>
Patchwork: https://patchwork.linux-mips.org/patch/6154/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
Diffstat (limited to 'arch/mips/kernel/r4k_switch.S')
| -rw-r--r-- | arch/mips/kernel/r4k_switch.S | 45 |
1 files changed, 43 insertions, 2 deletions
diff --git a/arch/mips/kernel/r4k_switch.S b/arch/mips/kernel/r4k_switch.S index 078de5eaca8f..cc78dd9a17c7 100644 --- a/arch/mips/kernel/r4k_switch.S +++ b/arch/mips/kernel/r4k_switch.S @@ -123,7 +123,7 @@ * Save a thread's fp context. */ LEAF(_save_fp) -#ifdef CONFIG_64BIT +#if defined(CONFIG_64BIT) || defined(CONFIG_CPU_MIPS32_R2) mfc0 t0, CP0_STATUS #endif fpu_save_double a0 t0 t1 # clobbers t1 @@ -134,7 +134,7 @@ LEAF(_save_fp) * Restore a thread's fp context. */ LEAF(_restore_fp) -#ifdef CONFIG_64BIT +#if defined(CONFIG_64BIT) || defined(CONFIG_CPU_MIPS32_R2) mfc0 t0, CP0_STATUS #endif fpu_restore_double a0 t0 t1 # clobbers t1 @@ -228,6 +228,47 @@ LEAF(_init_fpu) mtc1 t1, $f29 mtc1 t1, $f30 mtc1 t1, $f31 + +#ifdef CONFIG_CPU_MIPS32_R2 + .set push + .set mips64r2 + sll t0, t0, 5 # is Status.FR set? + bgez t0, 1f # no: skip setting upper 32b + + mthc1 t1, $f0 + mthc1 t1, $f1 + mthc1 t1, $f2 + mthc1 t1, $f3 + mthc1 t1, $f4 + mthc1 t1, $f5 + mthc1 t1, $f6 + mthc1 t1, $f7 + mthc1 t1, $f8 + mthc1 t1, $f9 + mthc1 t1, $f10 + mthc1 t1, $f11 + mthc1 t1, $f12 + mthc1 t1, $f13 + mthc1 t1, $f14 + mthc1 t1, $f15 + mthc1 t1, $f16 + mthc1 t1, $f17 + mthc1 t1, $f18 + mthc1 t1, $f19 + mthc1 t1, $f20 + mthc1 t1, $f21 + mthc1 t1, $f22 + mthc1 t1, $f23 + mthc1 t1, $f24 + mthc1 t1, $f25 + mthc1 t1, $f26 + mthc1 t1, $f27 + mthc1 t1, $f28 + mthc1 t1, $f29 + mthc1 t1, $f30 + mthc1 t1, $f31 +1: .set pop +#endif /* CONFIG_CPU_MIPS32_R2 */ #else .set mips3 dmtc1 t1, $f0 |