[POWERPC] Add support for FP emulation for the e300c2 core
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>
diff --git a/arch/powerpc/kernel/cputable.c b/arch/powerpc/kernel/cputable.c
index 9d1614c..11bfbaf 100644
--- a/arch/powerpc/kernel/cputable.c
+++ b/arch/powerpc/kernel/cputable.c
@@ -833,7 +833,7 @@
.pvr_mask = 0x7fff0000,
.pvr_value = 0x00840000,
.cpu_name = "e300c2",
- .cpu_features = CPU_FTRS_E300,
+ .cpu_features = CPU_FTRS_E300C2,
.cpu_user_features = PPC_FEATURE_32 | PPC_FEATURE_HAS_MMU,
.icache_bsize = 32,
.dcache_bsize = 32,
diff --git a/arch/powerpc/kernel/head_32.S b/arch/powerpc/kernel/head_32.S
index d88e182..9417cf5 100644
--- a/arch/powerpc/kernel/head_32.S
+++ b/arch/powerpc/kernel/head_32.S
@@ -437,6 +437,13 @@
/* Floating-point unavailable */
. = 0x800
FPUnavailable:
+BEGIN_FTR_SECTION
+/*
+ * Certain Freescale cores don't have a FPU and treat fp instructions
+ * as a FP Unavailable exception. Redirect to illegal/emulation handling.
+ */
+ b ProgramCheck
+END_FTR_SECTION_IFSET(CPU_FTR_FPU_UNAVAILABLE)
EXCEPTION_PROLOG
bne load_up_fpu /* if from user, just load it up */
addi r3,r1,STACK_FRAME_OVERHEAD
diff --git a/arch/powerpc/kernel/traps.c b/arch/powerpc/kernel/traps.c
index 0d4e203..fde820e 100644
--- a/arch/powerpc/kernel/traps.c
+++ b/arch/powerpc/kernel/traps.c
@@ -782,6 +782,8 @@
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)