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>

5 files changed, 68 insertions, 14 deletions

diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig
index f6f3b990d837..20b223ba654d 100644
--- a/arch/mips/Kconfig
+++ b/arch/mips/Kconfig
@@ -1427,6 +1427,9 @@ config CPU_SUPPORTS_64BIT_KERNEL
         bool
 config CPU_SUPPORTS_HUGEPAGES
         bool
+config MIPS_PGD_C0_CONTEXT
+        bool
+        default y if 64BIT && CPU_MIPSR2
 
 #
 # Set to y for ptrace access to watch registers.
diff --git a/arch/mips/include/asm/mmu_context.h b/arch/mips/include/asm/mmu_context.h
index 6083db586500..145bb81ccaa5 100644
--- a/arch/mips/include/asm/mmu_context.h
+++ b/arch/mips/include/asm/mmu_context.h
@@ -24,6 +24,33 @@
 #endif /* SMTC */
 #include <asm-generic/mm_hooks.h>
 
+#ifdef CONFIG_MIPS_PGD_C0_CONTEXT
+
+#define TLBMISS_HANDLER_SETUP_PGD(pgd)                          \
+        tlbmiss_handler_setup_pgd((unsigned long)(pgd))
+
+static inline void tlbmiss_handler_setup_pgd(unsigned long pgd)
+{
+        /* Check for swapper_pg_dir and convert to physical address. */
+        if ((pgd & CKSEG3) == CKSEG0)
+                pgd = CPHYSADDR(pgd);
+        write_c0_context(pgd << 11);
+}
+
+#define TLBMISS_HANDLER_SETUP()                                         \
+        do {                                                            \
+                TLBMISS_HANDLER_SETUP_PGD(swapper_pg_dir);              \
+                write_c0_xcontext((unsigned long) smp_processor_id() << 51); \
+        } while (0)
+
+
+static inline unsigned long get_current_pgd(void)
+{
+        return PHYS_TO_XKSEG_CACHED((read_c0_context() >> 11) & ~0xfffUL);
+}
+
+#else /* CONFIG_MIPS_PGD_C0_CONTEXT: using  pgd_current*/
+
 /*
  * For the fast tlb miss handlers, we keep a per cpu array of pointers
  * to the current pgd for each processor. Also, the proc. id is stuffed
@@ -46,7 +73,7 @@ extern unsigned long pgd_current[];
         back_to_back_c0_hazard();                                       \
         TLBMISS_HANDLER_SETUP_PGD(swapper_pg_dir)
 #endif
-
+#endif /* CONFIG_MIPS_PGD_C0_CONTEXT*/
 #if defined(CONFIG_CPU_R3000) || defined(CONFIG_CPU_TX39XX)
 
 #define ASID_INC        0x40
diff --git a/arch/mips/include/asm/stackframe.h b/arch/mips/include/asm/stackframe.h
index dd7e220e087b..3b6da3330e32 100644
--- a/arch/mips/include/asm/stackframe.h
+++ b/arch/mips/include/asm/stackframe.h
@@ -87,15 +87,19 @@
 #ifdef CONFIG_SMP
 #ifdef CONFIG_MIPS_MT_SMTC
 #define PTEBASE_SHIFT   19      /* TCBIND */
+#define CPU_ID_REG CP0_TCBIND
+#define CPU_ID_MFC0 mfc0
+#elif defined(CONFIG_MIPS_PGD_C0_CONTEXT)
+#define PTEBASE_SHIFT   48      /* XCONTEXT */
+#define CPU_ID_REG CP0_XCONTEXT
+#define CPU_ID_MFC0 MFC0
 #else
 #define PTEBASE_SHIFT   23      /* CONTEXT */
+#define CPU_ID_REG CP0_CONTEXT
+#define CPU_ID_MFC0 MFC0
 #endif
                 .macro  get_saved_sp    /* SMP variation */
-#ifdef CONFIG_MIPS_MT_SMTC
-                mfc0    k0, CP0_TCBIND
-#else
-                MFC0    k0, CP0_CONTEXT
-#endif
+                CPU_ID_MFC0     k0, CPU_ID_REG
 #if defined(CONFIG_32BIT) || defined(KBUILD_64BIT_SYM32)
                 lui     k1, %hi(kernelsp)
 #else
@@ -111,11 +115,7 @@
                 .endm
 
                 .macro  set_saved_sp stackp temp temp2
-#ifdef CONFIG_MIPS_MT_SMTC
-                mfc0    \temp, CP0_TCBIND
-#else
-                MFC0    \temp, CP0_CONTEXT
-#endif
+                CPU_ID_MFC0     \temp, CPU_ID_REG
                 LONG_SRL        \temp, PTEBASE_SHIFT
                 LONG_S  \stackp, kernelsp(\temp)
                 .endm
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: