[PATCH] ppc32: Fix errata for some G3 CPUs

Some G3 CPUs can crash in funny way if a store from an FPU register
instruction is executed on a register that has never been initialized since
power on.  This patch fixes it by making sure all FP registers have been
properly initialized at kernel boot and when waking from sleep.  It also makes
the code that decides wether HID0_BTIC and HID0_DPM are allowed on a given CPU
smarter (it can actually _clear_ them now if they are not allowed instead of
just setting them when they are allowed in case the firmware got them wrong)

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

2 files changed, 40 insertions, 6 deletions

diff --git a/arch/ppc/kernel/cpu_setup_6xx.S b/arch/ppc/kernel/cpu_setup_6xx.S
index 74f781b486a3..468721d9ebd2 100644
--- a/arch/ppc/kernel/cpu_setup_6xx.S
+++ b/arch/ppc/kernel/cpu_setup_6xx.S
@@ -30,12 +30,14 @@ _GLOBAL(__setup_cpu_604)
         blr
 _GLOBAL(__setup_cpu_750)
         mflr    r4
+        bl      __init_fpu_registers
         bl      setup_common_caches
         bl      setup_750_7400_hid0
         mtlr    r4
         blr
 _GLOBAL(__setup_cpu_750cx)
         mflr    r4
+        bl      __init_fpu_registers
         bl      setup_common_caches
         bl      setup_750_7400_hid0
         bl      setup_750cx
@@ -43,6 +45,7 @@ _GLOBAL(__setup_cpu_750cx)
         blr
 _GLOBAL(__setup_cpu_750fx)
         mflr    r4
+        bl      __init_fpu_registers
         bl      setup_common_caches
         bl      setup_750_7400_hid0
         bl      setup_750fx
@@ -50,6 +53,7 @@ _GLOBAL(__setup_cpu_750fx)
         blr
 _GLOBAL(__setup_cpu_7400)
         mflr    r4
+        bl      __init_fpu_registers
         bl      setup_7400_workarounds
         bl      setup_common_caches
         bl      setup_750_7400_hid0
@@ -57,6 +61,7 @@ _GLOBAL(__setup_cpu_7400)
         blr
 _GLOBAL(__setup_cpu_7410)
         mflr    r4
+        bl      __init_fpu_registers
         bl      setup_7410_workarounds
         bl      setup_common_caches
         bl      setup_750_7400_hid0
@@ -80,7 +85,7 @@ setup_common_caches:
         bne     1f                      /* don't invalidate the D-cache */
         ori     r8,r8,HID0_DCI          /* unless it wasn't enabled */
 1:      sync
-        mtspr   SPRN_HID0,r8                    /* enable and invalidate caches */
+        mtspr   SPRN_HID0,r8            /* enable and invalidate caches */
         sync
         mtspr   SPRN_HID0,r11           /* enable caches */
         sync
@@ -152,9 +157,13 @@ setup_7410_workarounds:
 setup_750_7400_hid0:
         mfspr   r11,SPRN_HID0
         ori     r11,r11,HID0_SGE | HID0_ABE | HID0_BHTE | HID0_BTIC
+        oris    r11,r11,HID0_DPM@h
 BEGIN_FTR_SECTION
-        oris    r11,r11,HID0_DPM@h      /* enable dynamic power mgmt */
-END_FTR_SECTION_IFCLR(CPU_FTR_NO_DPM)
+        xori    r11,r11,HID0_BTIC
+END_FTR_SECTION_IFSET(CPU_FTR_NO_BTIC)
+BEGIN_FTR_SECTION
+        xoris   r11,r11,HID0_DPM@h      /* disable dynamic power mgmt */
+END_FTR_SECTION_IFSET(CPU_FTR_NO_DPM)
         li      r3,HID0_SPD
         andc    r11,r11,r3              /* clear SPD: enable speculative */
         li      r3,0
@@ -218,13 +227,15 @@ setup_745x_specifics:
 
         /* All of the bits we have to set.....
          */
-        ori     r11,r11,HID0_SGE | HID0_FOLD | HID0_BHTE | HID0_LRSTK | HID0_BTIC
+        ori     r11,r11,HID0_SGE | HID0_FOLD | HID0_BHTE
+        ori     r11,r11,HID0_LRSTK | HID0_BTIC
+        oris    r11,r11,HID0_DPM@h
 BEGIN_FTR_SECTION
         xori    r11,r11,HID0_BTIC
 END_FTR_SECTION_IFSET(CPU_FTR_NO_BTIC)
 BEGIN_FTR_SECTION
-        oris    r11,r11,HID0_DPM@h      /* enable dynamic power mgmt */
-END_FTR_SECTION_IFCLR(CPU_FTR_NO_DPM)
+        xoris   r11,r11,HID0_DPM@h      /* disable dynamic power mgmt */
+END_FTR_SECTION_IFSET(CPU_FTR_NO_DPM)
 
         /* All of the bits we have to clear....
          */
@@ -248,6 +259,25 @@ END_FTR_SECTION_IFCLR(CPU_FTR_NO_DPM)
         isync
         blr
 
+/*
+ * Initialize the FPU registers. This is needed to work around an errata
+ * in some 750 cpus where using a not yet initialized FPU register after
+ * power on reset may hang the CPU
+ */
+_GLOBAL(__init_fpu_registers)
+        mfmsr   r10
+        ori     r11,r10,MSR_FP
+        mtmsr   r11
+        isync
+        addis   r9,r3,empty_zero_page@ha
+        addi    r9,r9,empty_zero_page@l
+        REST_32FPRS(0,r9)
+        sync
+        mtmsr   r10
+        isync
+        blr
+
+
 /* Definitions for the table use to save CPU states */
 #define CS_HID0         0
 #define CS_HID1         4
diff --git a/arch/ppc/platforms/pmac_sleep.S b/arch/ppc/platforms/pmac_sleep.S
index 3139b6766ad3..f459ade1bd63 100644
--- a/arch/ppc/platforms/pmac_sleep.S
+++ b/arch/ppc/platforms/pmac_sleep.S
@@ -267,6 +267,10 @@ grackle_wake_up:
         /* Restore various CPU config stuffs */
         bl      __restore_cpu_setup
 
+        /* Make sure all FPRs have been initialized */
+        bl      reloc_offset
+        bl      __init_fpu_registers
+
         /* Invalidate & enable L1 cache, we don't care about
          * whatever the ROM may have tried to write to memory
          */