path: root/arch/mips/math-emu
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authorRalf Baechle <ralf@linux-mips.org>2012-08-15 19:42:19 +0200
committerRalf Baechle <ralf@linux-mips.org>2012-12-13 18:15:27 +0100
commit51d943f07d3015998d448f9d8353f618e3fe5873 (patch)
tree7765f573133f87148a594d2e49b3b8543c7a77cf /arch/mips/math-emu
parent051ff44a8b508f8e8e342db3220d5ad8296c19ce (diff)
MIPS: Fix for warning from FPU emulation code
The default implementation of 'cpu_has_fpu' macro calls smp_processor_id() which causes this warning to be printed when preemption is enabled: [ 4.664000] Algorithmics/MIPS FPU Emulator v1.5 [ 4.676000] BUG: using smp_processor_id() in preemptible [00000000] code: ini [ 4.700000] caller is fpu_emulator_cop1Handler+0x434/0x27b8 This problem got introduced in November 2009 by af1d2af877ef6c36990671bc86a5b9c5bb50b1da (lmo) [MIPS: Fix emulation of 64-bit FPU on 64-bit CPUs.] rsp. da0bac33413b2888d3623dad3ad19ce76b688f07 (kernel.org) [MIPS: Fix emulation of 64-bit FPU on FPU-less 64-bit CPUs.] in 2.6.32. Fixed by rewriting cop1_64bit() to return a constant whenever possible but most importantly avoid the use pf cpu_has_fpu entirely. Signed-off-by: Ralf Baechle <ralf@linux-mips.org> Reported-by: Jayachandran C <jchandra@broadcom.com> Initial-patch-by: Jayachandran C <jchandra@broadcom.com> Patchwork: https://patchwork.linux-mips.org/patch/4225/
Diffstat (limited to 'arch/mips/math-emu')
1 files changed, 8 insertions, 7 deletions
diff --git a/arch/mips/math-emu/cp1emu.c b/arch/mips/math-emu/cp1emu.c
index a03bf00a1a9..47c77e7ffbf 100644
--- a/arch/mips/math-emu/cp1emu.c
+++ b/arch/mips/math-emu/cp1emu.c
@@ -171,16 +171,17 @@ static int isBranchInstr(mips_instruction * i)
* In the Linux kernel, we support selection of FPR format on the
* basis of the Status.FR bit. If an FPU is not present, the FR bit
* is hardwired to zero, which would imply a 32-bit FPU even for
- * 64-bit CPUs. For 64-bit kernels with no FPU we use TIF_32BIT_REGS
- * as a proxy for the FR bit so that a 64-bit FPU is emulated. In any
- * case, for a 32-bit kernel which uses the O32 MIPS ABI, only the
- * even FPRs are used (Status.FR = 0).
+ * 64-bit CPUs so we rather look at TIF_32BIT_REGS.
+ * FPU emu is slow and bulky and optimizing this function offers fairly
+ * sizeable benefits so we try to be clever and make this function return
+ * a constant whenever possible, that is on 64-bit kernels without O32
+ * compatibility enabled and on 32-bit kernels.
static inline int cop1_64bit(struct pt_regs *xcp)
- if (cpu_has_fpu)
- return xcp->cp0_status & ST0_FR;
-#ifdef CONFIG_64BIT
+#if defined(CONFIG_64BIT) && !defined(CONFIG_MIPS32_O32)
+ return 1;
+#elif defined(CONFIG_64BIT) && defined(CONFIG_MIPS32_O32)
return !test_thread_flag(TIF_32BIT_REGS);
return 0;