[SPARC64]: Fix boot failures on SunBlade-150

The sequence to move over to the Linux trap tables from
the firmware ones needs to be more air tight.  It turns
out that to be %100 safe we do need to be able to translate
OBP mappings in our TLB miss handlers early.

In order not to eat up a lot of kernel image memory with
static page tables, just use the translations array in
the OBP TLB miss handlers.  That solves the bulk of the
problem.

Furthermore, to make sure the OBP TLB miss path will work
even before the fixed MMU globals are loaded, explicitly
load %g1 to TLB_SFSR at the beginning of the i-TLB and
d-TLB miss handlers.

To ease the OBP TLB miss walking of the prom_trans[] array,
we sort it then delete all of the non-OBP entries in there
(for example, there are entries for the kernel image itself
which we're not interested in at all).

We also save about 32K of kernel image size with this change.
Not a bad side effect :-)

There are still some reasons why trampoline.S can't use the
setup_trap_table() yet.  The most noteworthy are:

1) OBP boots secondary processors with non-bias'd stack for
   some reason.  This is easily fixed by using a small bootup
   stack in the kernel image explicitly for this purpose.

2) Doing a firmware call via the normal C call prom_set_trap_table()
   goes through the whole OBP enter/exit sequence that saves and
   restores OBP and Linux kernel state in the MMUs.  This path
   unfortunately does a "flush %g6" while loading up the OBP locked
   TLB entries for the firmware call.

   If we setup the %g6 in the trampoline.S code properly, that
   is in the PAGE_OFFSET linear mapping, but we're not on the
   kernel trap table yet so those addresses won't translate properly.

   One idea is to do a by-hand firmware call like we do in the
   early bootup code and elsewhere here in trampoline.S  But this
   fails as well, as aparently the secondary processors are not
   booted with OBP's special locked TLB entries loaded.  These
   are necessary for the firwmare to processes TLB misses correctly
   up until the point where we take over the trap table.

This does need to be resolved at some point.

Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 5 insertions, 9 deletions

diff --git a/arch/sparc64/kernel/dtlb_base.S b/arch/sparc64/kernel/dtlb_base.S
index 702d349c1e88..6528786840c0 100644
--- a/arch/sparc64/kernel/dtlb_base.S
+++ b/arch/sparc64/kernel/dtlb_base.S
@@ -53,19 +53,18 @@
  * be guaranteed to be 0 ... mmu_context.h does guarantee this
  * by only using 10 bits in the hwcontext value.
  */
-#define CREATE_VPTE_OFFSET1(r1, r2)
+#define CREATE_VPTE_OFFSET1(r1, r2) nop
 #define CREATE_VPTE_OFFSET2(r1, r2) \
                                 srax    r1, 10, r2
-#define CREATE_VPTE_NOP         nop
 #else
 #define CREATE_VPTE_OFFSET1(r1, r2) \
                                 srax    r1, PAGE_SHIFT, r2
 #define CREATE_VPTE_OFFSET2(r1, r2) \
                                 sllx    r2, 3, r2
-#define CREATE_VPTE_NOP
 #endif
 
 /* DTLB ** ICACHE line 1: Quick user TLB misses         */
+        mov             TLB_SFSR, %g1
         ldxa            [%g1 + %g1] ASI_DMMU, %g4       ! Get TAG_ACCESS
         andcc           %g4, TAG_CONTEXT_BITS, %g0      ! From Nucleus?
 from_tl1_trap:
@@ -74,18 +73,16 @@ from_tl1_trap:
         be,pn           %xcc, kvmap                     ! Yep, special processing
          CREATE_VPTE_OFFSET2(%g4, %g6)                  ! Create VPTE offset
         cmp             %g5, 4                          ! Last trap level?
-        be,pn           %xcc, longpath                  ! Yep, cannot risk VPTE miss
-         nop                                            ! delay slot
 
 /* DTLB ** ICACHE line 2: User finish + quick kernel TLB misses */
+        be,pn           %xcc, longpath                  ! Yep, cannot risk VPTE miss
+         nop                                            ! delay slot
         ldxa            [%g3 + %g6] ASI_S, %g5          ! Load VPTE
 1:      brgez,pn        %g5, longpath                   ! Invalid, branch out
          nop                                            ! Delay-slot
 9:      stxa            %g5, [%g0] ASI_DTLB_DATA_IN     ! Reload TLB
         retry                                           ! Trap return
         nop
-        nop
-        nop
 
 /* DTLB ** ICACHE line 3: winfixups+real_faults         */
 longpath:
@@ -106,8 +103,7 @@ longpath:
         nop
         nop
         nop
-        CREATE_VPTE_NOP
+        nop
 
 #undef CREATE_VPTE_OFFSET1
 #undef CREATE_VPTE_OFFSET2
-#undef CREATE_VPTE_NOP