MIPS: Put PGD in C0_CONTEXT for 64-bit R2 processors.

Processors that support the mips64r2 ISA can in four instructions
convert a shifted PGD pointer stored in the upper bits of c0_context
into a usable pointer.  By doing this we save a memory load and
associated potential cache miss in the TLB exception handlers.

Since the upper bits of c0_context were holding the CPU number, we
move this to the upper bits of c0_xcontext which doesn't have enough
bits to hold the PGD pointer, but has plenty for the CPU number.

Signed-off-by: David Daney <ddaney@caviumnetworks.com>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

2 files changed, 27 insertions, 3 deletions

diff --git a/arch/mips/mm/init.c b/arch/mips/mm/init.c
index 8d1f4f363049..9e8d00389eef 100644
--- a/arch/mips/mm/init.c
+++ b/arch/mips/mm/init.c
@@ -462,7 +462,9 @@ void __init_refok free_initmem(void)
                         __pa_symbol(&__init_end));
 }
 
+#ifndef CONFIG_MIPS_PGD_C0_CONTEXT
 unsigned long pgd_current[NR_CPUS];
+#endif
 /*
  * On 64-bit we've got three-level pagetables with a slightly
  * different layout ...
diff --git a/arch/mips/mm/tlbex.c b/arch/mips/mm/tlbex.c
index bb1719a55d22..3d0baa4a842d 100644
--- a/arch/mips/mm/tlbex.c
+++ b/arch/mips/mm/tlbex.c
@@ -160,6 +160,12 @@ static u32 tlb_handler[128] __cpuinitdata;
 static struct uasm_label labels[128] __cpuinitdata;
 static struct uasm_reloc relocs[128] __cpuinitdata;
 
+#ifndef CONFIG_MIPS_PGD_C0_CONTEXT
+/*
+ * CONFIG_MIPS_PGD_C0_CONTEXT implies 64 bit and lack of pgd_current,
+ * we cannot do r3000 under these circumstances.
+ */
+
 /*
  * The R3000 TLB handler is simple.
  */
@@ -199,6 +205,7 @@ static void __cpuinit build_r3000_tlb_refill_handler(void)
 
         dump_handler((u32 *)ebase, 32);
 }
+#endif /* CONFIG_MIPS_PGD_C0_CONTEXT */
 
 /*
  * The R4000 TLB handler is much more complicated. We have two
@@ -497,8 +504,9 @@ static void __cpuinit
 build_get_pmde64(u32 **p, struct uasm_label **l, struct uasm_reloc **r,
                  unsigned int tmp, unsigned int ptr)
 {
+#ifndef CONFIG_MIPS_PGD_C0_CONTEXT
         long pgdc = (long)pgd_current;
-
+#endif
         /*
          * The vmalloc handling is not in the hotpath.
          */
@@ -506,7 +514,15 @@ build_get_pmde64(u32 **p, struct uasm_label **l, struct uasm_reloc **r,
         uasm_il_bltz(p, r, tmp, label_vmalloc);
         /* No uasm_i_nop needed here, since the next insn doesn't touch TMP. */
 
-#ifdef CONFIG_SMP
+#ifdef CONFIG_MIPS_PGD_C0_CONTEXT
+        /*
+         * &pgd << 11 stored in CONTEXT [23..63].
+         */
+        UASM_i_MFC0(p, ptr, C0_CONTEXT);
+        uasm_i_dins(p, ptr, 0, 0, 23); /* Clear lower 23 bits of context. */
+        uasm_i_ori(p, ptr, ptr, 0x540); /* 1 0  1 0 1  << 6  xkphys cached */
+        uasm_i_drotr(p, ptr, ptr, 11);
+#elif defined(CONFIG_SMP)
 # ifdef  CONFIG_MIPS_MT_SMTC
         /*
          * SMTC uses TCBind value as "CPU" index
@@ -520,7 +536,7 @@ build_get_pmde64(u32 **p, struct uasm_label **l, struct uasm_reloc **r,
          */
         uasm_i_dmfc0(p, ptr, C0_CONTEXT);
         uasm_i_dsrl(p, ptr, ptr, 23);
-#endif
+# endif
         UASM_i_LA_mostly(p, tmp, pgdc);
         uasm_i_daddu(p, ptr, ptr, tmp);
         uasm_i_dmfc0(p, tmp, C0_BADVADDR);
@@ -1033,6 +1049,7 @@ build_pte_modifiable(u32 **p, struct uasm_reloc **r,
         iPTE_LW(p, pte, ptr);
 }
 
+#ifndef CONFIG_MIPS_PGD_C0_CONTEXT
 /*
  * R3000 style TLB load/store/modify handlers.
  */
@@ -1184,6 +1201,7 @@ static void __cpuinit build_r3000_tlb_modify_handler(void)
 
         dump_handler(handle_tlbm, ARRAY_SIZE(handle_tlbm));
 }
+#endif /* CONFIG_MIPS_PGD_C0_CONTEXT */
 
 /*
  * R4000 style TLB load/store/modify handlers.
@@ -1400,6 +1418,7 @@ void __cpuinit build_tlb_refill_handler(void)
         case CPU_TX3912:
         case CPU_TX3922:
         case CPU_TX3927:
+#ifndef CONFIG_MIPS_PGD_C0_CONTEXT
                 build_r3000_tlb_refill_handler();
                 if (!run_once) {
                         build_r3000_tlb_load_handler();
@@ -1407,6 +1426,9 @@ void __cpuinit build_tlb_refill_handler(void)
                         build_r3000_tlb_modify_handler();
                         run_once++;
                 }
+#else
+                panic("No R3000 TLB refill handler");
+#endif
                 break;
 
         case CPU_R6000: