Fix the VFP handling on the Feroceon CPU

This CPU generates synchronous VFP exceptions in a non-standard way -
the FPEXC.EX bit set but without the FPSCR.IXE bit being set like in the
VFP subarchitecture 1 or just the FPEXC.DEX bit like in VFP
subarchitecture 2. The main problem is that the faulty instruction
(which needs to be emulated in software) will be restarted several times
(normally until a context switch disables the VFP). This patch ensures
that the VFP exception is treated as synchronous.

Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Cc: Nicolas Pitre <nico@cam.org>

2 files changed, 6 insertions, 0 deletions

diff --git a/arch/arm/vfp/vfphw.S b/arch/arm/vfp/vfphw.S
index 83c4e384b16..1aeae38725d 100644
--- a/arch/arm/vfp/vfphw.S
+++ b/arch/arm/vfp/vfphw.S
@@ -100,6 +100,7 @@ ENTRY(vfp_support_entry)
         beq     no_old_VFP_process
         VFPFSTMIA r4, r5                @ save the working registers
         VFPFMRX r5, FPSCR               @ current status
+#ifndef CONFIG_CPU_FEROCEON
         tst     r1, #FPEXC_EX           @ is there additional state to save?
         beq     1f
         VFPFMRX r6, FPINST              @ FPINST (only if FPEXC.EX is set)
@@ -107,6 +108,7 @@ ENTRY(vfp_support_entry)
         beq     1f
         VFPFMRX r8, FPINST2             @ FPINST2 if needed (and present)
 1:
+#endif
         stmia   r4, {r1, r5, r6, r8}    @ save FPEXC, FPSCR, FPINST, FPINST2
                                         @ and point r4 at the word at the
                                         @ start of the register dump
@@ -119,6 +121,7 @@ no_old_VFP_process:
         VFPFLDMIA r10, r5               @ reload the working registers while
                                         @ FPEXC is in a safe state
         ldmia   r10, {r1, r5, r6, r8}   @ load FPEXC, FPSCR, FPINST, FPINST2
+#ifndef CONFIG_CPU_FEROCEON
         tst     r1, #FPEXC_EX           @ is there additional state to restore?
         beq     1f
         VFPFMXR FPINST, r6              @ restore FPINST (only if FPEXC.EX is set)
@@ -126,6 +129,7 @@ no_old_VFP_process:
         beq     1f
         VFPFMXR FPINST2, r8             @ FPINST2 if needed (and present)
 1:
+#endif
         VFPFMXR FPSCR, r5               @ restore status
 
 check_for_exception:
diff --git a/arch/arm/vfp/vfpmodule.c b/arch/arm/vfp/vfpmodule.c
index 01599c4ef72..2d7423af119 100644
--- a/arch/arm/vfp/vfpmodule.c
+++ b/arch/arm/vfp/vfpmodule.c
@@ -253,12 +253,14 @@ void VFP_bounce(u32 trigger, u32 fpexc, struct pt_regs *regs)
         }
 
         if (fpexc & FPEXC_EX) {
+#ifndef CONFIG_CPU_FEROCEON
                 /*
                  * Asynchronous exception. The instruction is read from FPINST
                  * and the interrupted instruction has to be restarted.
                  */
                 trigger = fmrx(FPINST);
                 regs->ARM_pc -= 4;
+#endif
         } else if (!(fpexc & FPEXC_DEX)) {
                 /*
                  * Illegal combination of bits. It can be caused by an