sh: TLB miss fast-path optimizations.

Handle simple TLB miss faults which can be resolved completely
from the page table in assembler.

Signed-off-by: Stuart Menefy <stuart.menefy@st.com>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>

2 files changed, 197 insertions, 28 deletions

diff --git a/arch/sh/kernel/cpu/sh3/entry.S b/arch/sh/kernel/cpu/sh3/entry.S
index 869d56fb7d63..5de99b498738 100644
--- a/arch/sh/kernel/cpu/sh3/entry.S
+++ b/arch/sh/kernel/cpu/sh3/entry.S
@@ -13,8 +13,10 @@
 #include <linux/linkage.h>
 #include <asm/asm-offsets.h>
 #include <asm/thread_info.h>
-#include <asm/cpu/mmu_context.h>
 #include <asm/unistd.h>
+#include <asm/cpu/mmu_context.h>
+#include <asm/pgtable.h>
+#include <asm/page.h>
 
 ! NOTE:
 ! GNU as (as of 2.9.1) changes bf/s into bt/s and bra, when the address
@@ -136,29 +138,14 @@ ENTRY(tlb_protection_violation_store)
 
 call_dpf:
         mov.l   1f, r0
-        mov     r5, r8
-        mov.l   @r0, r6
-        mov     r6, r9
-        mov.l   2f, r0
-        sts     pr, r10
-        jsr     @r0
-         mov    r15, r4
-        !
-        tst     r0, r0
-        bf/s    0f
-         lds    r10, pr
-        rts
-         nop
-0:      sti
+        mov.l   @r0, r6         ! address
         mov.l   3f, r0
-        mov     r9, r6
-        mov     r8, r5
+        sti
         jmp     @r0
-         mov    r15, r4
+         mov    r15, r4         ! regs
 
         .align 2
 1:      .long   MMU_TEA
-2:      .long   __do_page_fault
 3:      .long   do_page_fault
 
         .align  2
@@ -344,9 +331,176 @@ general_exception:
 2:      .long   ret_from_exception
 !
 !
+
+/* This code makes some assumptions to improve performance.
+ * Make sure they are stil true. */
+#if PTRS_PER_PGD != PTRS_PER_PTE
+#error PDG and PTE sizes don't match
+#endif
+
+/* gas doesn't flag impossible values for mov #immediate as an error */
+#if (_PAGE_PRESENT >> 2) > 0x7f
+#error cannot load PAGE_PRESENT as an immediate
+#endif
+#if _PAGE_DIRTY > 0x7f
+#error cannot load PAGE_DIRTY as an immediate
+#endif
+#if (_PAGE_PRESENT << 2) != _PAGE_ACCESSED
+#error cannot derive PAGE_ACCESSED from PAGE_PRESENT
+#endif
+
+#if defined(CONFIG_CPU_SH4)
+#define ldmmupteh(r)    mov.l   8f, r
+#else
+#define ldmmupteh(r)    mov     #MMU_PTEH, r
+#endif
+
         .balign         1024,0,1024
 tlb_miss:
-        mov.l   1f, k2
+#ifdef COUNT_EXCEPTIONS
+        ! Increment the counts
+        mov.l   9f, k1
+        mov.l   @k1, k2
+        add     #1, k2
+        mov.l   k2, @k1
+#endif
+
+        ! k0 scratch
+        ! k1 pgd and pte pointers
+        ! k2 faulting address
+        ! k3 pgd and pte index masks
+        ! k4 shift
+
+        ! Load up the pgd entry (k1)
+
+        ldmmupteh(k0)                   !  9 LS (latency=2)     MMU_PTEH
+
+        mov.w   4f, k3                  !  8 LS (latency=2)     (PTRS_PER_PGD-1) << 2
+        mov     #-(PGDIR_SHIFT-2), k4   !  6 EX
+
+        mov.l   @(MMU_TEA-MMU_PTEH,k0), k2      ! 18 LS (latency=2)
+
+        mov.l   @(MMU_TTB-MMU_PTEH,k0), k1      ! 18 LS (latency=2)
+
+        mov     k2, k0                  !   5 MT (latency=0)
+        shld    k4, k0                  !  99 EX
+
+        and     k3, k0                  !  78 EX
+
+        mov.l   @(k0, k1), k1           !  21 LS (latency=2)
+        mov     #-(PAGE_SHIFT-2), k4    !   6 EX
+
+        ! Load up the pte entry (k2)
+
+        mov     k2, k0                  !   5 MT (latency=0)
+        shld    k4, k0                  !  99 EX
+
+        tst     k1, k1                  !  86 MT
+
+        bt      20f                     ! 110 BR
+
+        and     k3, k0                  !  78 EX
+        mov.w   5f, k4                  !   8 LS (latency=2)    _PAGE_PRESENT
+
+        mov.l   @(k0, k1), k2           !  21 LS (latency=2)
+        add     k0, k1                  !  49 EX
+
+#ifdef CONFIG_CPU_HAS_PTEA
+        ! Test the entry for present and _PAGE_ACCESSED
+
+        mov     #-28, k3                !   6 EX
+        mov     k2, k0                  !   5 MT (latency=0)
+
+        tst     k4, k2                  !  68 MT
+        shld    k3, k0                  !  99 EX
+
+        bt      20f                     ! 110 BR
+
+        ! Set PTEA register
+        ! MMU_PTEA = ((pteval >> 28) & 0xe) | (pteval & 0x1)
+        !
+        ! k0=pte>>28, k1=pte*, k2=pte, k3=<unused>, k4=_PAGE_PRESENT
+
+        and     #0xe, k0                !  79 EX
+
+        mov     k0, k3                  !   5 MT (latency=0)
+        mov     k2, k0                  !   5 MT (latency=0)
+
+        and     #1, k0                  !  79 EX
+
+        or      k0, k3                  !  82 EX
+
+        ldmmupteh(k0)                   !   9 LS (latency=2)
+        shll2   k4                      ! 101 EX                _PAGE_ACCESSED
+
+        tst     k4, k2                  !  68 MT
+
+        mov.l   k3, @(MMU_PTEA-MMU_PTEH,k0)     ! 27 LS
+
+        mov.l   7f, k3                  !   9 LS (latency=2)    _PAGE_FLAGS_HARDWARE_MASK
+
+        ! k0=MMU_PTEH, k1=pte*, k2=pte, k3=_PAGE_FLAGS_HARDWARE, k4=_PAGE_ACCESSED
+#else
+
+        ! Test the entry for present and _PAGE_ACCESSED
+
+        mov.l   7f, k3                  !   9 LS (latency=2)    _PAGE_FLAGS_HARDWARE_MASK
+        tst     k4, k2                  !  68 MT
+
+        shll2   k4                      ! 101 EX                _PAGE_ACCESSED
+        ldmmupteh(k0)                   !   9 LS (latency=2)
+
+        bt      20f                     ! 110 BR
+        tst     k4, k2                  !  68 MT
+
+        ! k0=MMU_PTEH, k1=pte*, k2=pte, k3=_PAGE_FLAGS_HARDWARE, k4=_PAGE_ACCESSED
+
+#endif
+
+        ! Set up the entry
+
+        and     k2, k3                  !  78 EX
+        bt/s    10f                     ! 108 BR
+
+         mov.l  k3, @(MMU_PTEL-MMU_PTEH,k0)     ! 27 LS
+
+        ldtlb                           ! 128 CO
+
+        ! At least one instruction between ldtlb and rte
+        nop                             ! 119 NOP
+
+        rte                             ! 126 CO
+
+         nop                            ! 119 NOP
+
+
+10:     or      k4, k2                  !  82 EX
+
+        ldtlb                           ! 128 CO
+
+        ! At least one instruction between ldtlb and rte
+        mov.l   k2, @k1                 !  27 LS
+
+        rte                             ! 126 CO
+
+        ! Note we cannot execute mov here, because it is executed after
+        ! restoring SSR, so would be executed in user space.
+         nop                            ! 119 NOP
+
+
+        .align 5
+        ! Once cache line if possible...
+1:      .long   swapper_pg_dir
+4:      .short  (PTRS_PER_PGD-1) << 2
+5:      .short  _PAGE_PRESENT
+7:      .long   _PAGE_FLAGS_HARDWARE_MASK
+8:      .long   MMU_PTEH
+#ifdef COUNT_EXCEPTIONS
+9:      .long   exception_count_miss
+#endif
+
+        ! Either pgd or pte not present
+20:     mov.l   1f, k2
         mov.l   4f, k3
         bra     handle_exception
          mov.l  @k2, k2
@@ -496,6 +650,15 @@ skip_save:
         bf      interrupt_exception
         shlr2   r8
         shlr    r8
+
+#ifdef COUNT_EXCEPTIONS
+        mov.l   5f, r9
+        add     r8, r9
+        mov.l   @r9, r10
+        add     #1, r10
+        mov.l   r10, @r9
+#endif
+
         mov.l   4f, r9
         add     r8, r9
         mov.l   @r9, r9
@@ -509,6 +672,9 @@ skip_save:
 2:      .long   0x000080f0      ! FD=1, IMASK=15
 3:      .long   0xcfffffff      ! RB=0, BL=0
 4:      .long   exception_handling_table
+#ifdef COUNT_EXCEPTIONS
+5:      .long   exception_count_table
+#endif
 
 interrupt_exception:
         mov.l   1f, r9
diff --git a/arch/sh/kernel/cpu/sh4/probe.c b/arch/sh/kernel/cpu/sh4/probe.c
index c294de1e14a3..afe0f1b1c030 100644
--- a/arch/sh/kernel/cpu/sh4/probe.c
+++ b/arch/sh/kernel/cpu/sh4/probe.c
@@ -79,16 +79,16 @@ int __init detect_cpu_and_cache_system(void)
         case 0x205:
                 cpu_data->type = CPU_SH7750;
                 cpu_data->flags |= CPU_HAS_P2_FLUSH_BUG | CPU_HAS_FPU |
-                                   CPU_HAS_PERF_COUNTER | CPU_HAS_PTEA;
+                                   CPU_HAS_PERF_COUNTER;
                 break;
         case 0x206:
                 cpu_data->type = CPU_SH7750S;
                 cpu_data->flags |= CPU_HAS_P2_FLUSH_BUG | CPU_HAS_FPU |
-                                   CPU_HAS_PERF_COUNTER | CPU_HAS_PTEA;
+                                   CPU_HAS_PERF_COUNTER;
                 break;
         case 0x1100:
                 cpu_data->type = CPU_SH7751;
-                cpu_data->flags |= CPU_HAS_FPU | CPU_HAS_PTEA;
+                cpu_data->flags |= CPU_HAS_FPU;
                 break;
         case 0x2000:
                 cpu_data->type = CPU_SH73180;
@@ -126,23 +126,22 @@ int __init detect_cpu_and_cache_system(void)
                 break;
         case 0x8000:
                 cpu_data->type = CPU_ST40RA;
-                cpu_data->flags |= CPU_HAS_FPU | CPU_HAS_PTEA;
+                cpu_data->flags |= CPU_HAS_FPU;
                 break;
         case 0x8100:
                 cpu_data->type = CPU_ST40GX1;
-                cpu_data->flags |= CPU_HAS_FPU | CPU_HAS_PTEA;
+                cpu_data->flags |= CPU_HAS_FPU;
                 break;
         case 0x700:
                 cpu_data->type = CPU_SH4_501;
                 cpu_data->icache.ways = 2;
                 cpu_data->dcache.ways = 2;
-                cpu_data->flags |= CPU_HAS_PTEA;
                 break;
         case 0x600:
                 cpu_data->type = CPU_SH4_202;
                 cpu_data->icache.ways = 2;
                 cpu_data->dcache.ways = 2;
-                cpu_data->flags |= CPU_HAS_FPU | CPU_HAS_PTEA;
+                cpu_data->flags |= CPU_HAS_FPU;
                 break;
         case 0x500 ... 0x501:
                 switch (prr) {
@@ -160,7 +159,7 @@ int __init detect_cpu_and_cache_system(void)
                 cpu_data->icache.ways = 2;
                 cpu_data->dcache.ways = 2;
 
-                cpu_data->flags |= CPU_HAS_FPU | CPU_HAS_PTEA;
+                cpu_data->flags |= CPU_HAS_FPU;
 
                 break;
         default:
@@ -173,6 +172,10 @@ int __init detect_cpu_and_cache_system(void)
         cpu_data->dcache.ways = 1;
 #endif
 
+#ifdef CONFIG_CPU_HAS_PTEA
+        cpu_data->flags |= CPU_HAS_PTEA;
+#endif
+
         /*
          * On anything that's not a direct-mapped cache, look to the CVR
          * for I/D-cache specifics.