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[POWERPC] Add support for FP emulation for the e300c2 core

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The e300c2 has no FPU.  Its MSR[FP] is grounded to zero.  If an attempt
is made to execute a floating point instruction (including floating-point
load, store, or move instructions), the e300c2 takes a floating-point
unavailable interrupt.

This patch adds support for FP emulation on the e300c2 by declaring a
new CPU_FTR_FP_TAKES_FPUNAVAIL, where FP unavail interrupts are
intercepted and redirected to the ProgramCheck exception path for
correct emulation handling.

(If we run out of CPU_FTR bits we could look to reclaim this bit by adding
support to test the cpu_user_features for PPC_FEATURE_HAS_FPU instead)

It adds a nop to the exception path for 32-bit processors with a FPU.

Signed-off-by: Kim Phillips <kim.phillips@freescale.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>
This commit is contained in:
Kim Phillips
2006-12-08 02:43:30 -06:00
committed by Kumar Gala
parent c99767974e
commit aa42c69c67
5 changed files with 19 additions and 4 deletions
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arch/powerpc/kernel/traps.c
+2
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@@ -782,6 +782,8 @@ void __kprobes program_check_exception(struct pt_regs *regs)
unsigned int reason = get_reason(regs);
extern int do_mathemu(struct pt_regs *regs);
/* We can now get here via a FP Unavailable exception if the core
* has no FPU, in that case no reason flags will be set */
#ifdef CONFIG_MATH_EMULATION
/* (reason & REASON_ILLEGAL) would be the obvious thing here,
* but there seems to be a hardware bug on the 405GP (RevD)