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[PATCH 2/3] MIPS: mm: Use scratch for PGD when !CONFIG_MIPS_PGD_C0_CONTE

To: linux-mips@linux-mips.org, ralf@linux-mips.org
Subject: [PATCH 2/3] MIPS: mm: Use scratch for PGD when !CONFIG_MIPS_PGD_C0_CONTEXT
From: "Jayachandran C" <jchandra@broadcom.com>
Date: Tue, 8 Jan 2013 18:26:28 +0530
Cc: "Jayachandran C" <jchandra@broadcom.com>
In-reply-to: <1357649789-3423-1-git-send-email-jchandra@broadcom.com>
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Allow usage of scratch register for current pgd even when
MIPS_PGD_C0_CONTEXT is not configured.  MIPS_PGD_C0_CONTEXT is set
for 64r2 platforms to indicate availability of Xcontext for saving
cpuid, and this was also tied to using scratch registers for PGD.

This commit will allow usage of scratch register to store the current
pgd, if one can be allocated for the platform, even in other cases
(i.e when MIPS_PGD_C0_CONTEXT is not set). The processor id will be
kept in the CP0 Context register in this case.

The code to store the current pgd for the TLB miss handler is now
generated in all cases, and if scratch register is available, the
pgd is also stored in the scratch register.

Signed-off-by: Jayachandran C <jchandra@broadcom.com>
---
 arch/mips/include/asm/mmu_context.h |    8 +-
 arch/mips/mm/tlbex.c                |  139 ++++++++++++++++++++++-------------
 2 files changed, 91 insertions(+), 56 deletions(-)

diff --git a/arch/mips/include/asm/mmu_context.h 
b/arch/mips/include/asm/mmu_context.h
index 9b02cfb..9d06a96 100644
--- a/arch/mips/include/asm/mmu_context.h
+++ b/arch/mips/include/asm/mmu_context.h
@@ -24,13 +24,12 @@
 #endif /* SMTC */
 #include <asm-generic/mm_hooks.h>
 
-#ifdef CONFIG_MIPS_PGD_C0_CONTEXT
+extern void tlbmiss_handler_setup_pgd(unsigned long pgd);
 
 #define TLBMISS_HANDLER_SETUP_PGD(pgd)                         \
        tlbmiss_handler_setup_pgd((unsigned long)(pgd))
 
-extern void tlbmiss_handler_setup_pgd(unsigned long pgd);
-
+#ifdef CONFIG_MIPS_PGD_C0_CONTEXT
 #define TLBMISS_HANDLER_SETUP()                                                
\
        do {                                                            \
                TLBMISS_HANDLER_SETUP_PGD(swapper_pg_dir);              \
@@ -46,9 +45,6 @@ extern void tlbmiss_handler_setup_pgd(unsigned long pgd);
  */
 extern unsigned long pgd_current[];
 
-#define TLBMISS_HANDLER_SETUP_PGD(pgd) \
-       pgd_current[smp_processor_id()] = (unsigned long)(pgd)
-
 #ifdef CONFIG_32BIT
 #define TLBMISS_HANDLER_SETUP()                                                
\
        write_c0_context((unsigned long) smp_processor_id() << 25);     \
diff --git a/arch/mips/mm/tlbex.c b/arch/mips/mm/tlbex.c
index c14f63f..ffbdedf 100644
--- a/arch/mips/mm/tlbex.c
+++ b/arch/mips/mm/tlbex.c
@@ -805,11 +805,11 @@ build_get_pmde64(u32 **p, struct uasm_label **l, struct 
uasm_reloc **r,
        }
        /* No uasm_i_nop needed here, since the next insn doesn't touch TMP. */
 
-#ifdef CONFIG_MIPS_PGD_C0_CONTEXT
        if (pgd_reg != -1) {
                /* pgd is in pgd_reg */
                UASM_i_MFC0(p, ptr, c0_kscratch, pgd_reg);
        } else {
+#ifdef CONFIG_MIPS_PGD_C0_CONTEXT
                /*
                 * &pgd << 11 stored in CONTEXT [23..63].
                 */
@@ -821,30 +821,32 @@ build_get_pmde64(u32 **p, struct uasm_label **l, struct 
uasm_reloc **r,
                /* 1 0  1 0 1  << 6  xkphys cached */
                uasm_i_ori(p, ptr, ptr, 0x540);
                uasm_i_drotr(p, ptr, ptr, 11);
-       }
-#elif defined(CONFIG_SMP)
+#else
+#if defined(CONFIG_SMP)
 # ifdef  CONFIG_MIPS_MT_SMTC
-       /*
-        * SMTC uses TCBind value as "CPU" index
-        */
-       uasm_i_mfc0(p, ptr, C0_TCBIND);
-       uasm_i_dsrl_safe(p, ptr, ptr, 19);
+               /*
+                * SMTC uses TCBind value as "CPU" index
+                */
+               uasm_i_mfc0(p, ptr, C0_TCBIND);
+               uasm_i_dsrl_safe(p, ptr, ptr, 19);
 # else
-       /*
-        * 64 bit SMP running in XKPHYS has smp_processor_id() << 3
-        * stored in CONTEXT.
-        */
-       uasm_i_dmfc0(p, ptr, C0_CONTEXT);
-       uasm_i_dsrl_safe(p, ptr, ptr, 23);
+               /*
+                * 64 bit SMP running in XKPHYS has smp_processor_id() << 3
+                * stored in CONTEXT.
+                */
+               uasm_i_dmfc0(p, ptr, C0_CONTEXT);
+               uasm_i_dsrl_safe(p, ptr, ptr, 23);
 # endif
-       UASM_i_LA_mostly(p, tmp, pgdc);
-       uasm_i_daddu(p, ptr, ptr, tmp);
-       uasm_i_dmfc0(p, tmp, C0_BADVADDR);
-       uasm_i_ld(p, ptr, uasm_rel_lo(pgdc), ptr);
+               UASM_i_LA_mostly(p, tmp, pgdc);
+               uasm_i_daddu(p, ptr, ptr, tmp);
+               uasm_i_dmfc0(p, tmp, C0_BADVADDR);
+               uasm_i_ld(p, ptr, uasm_rel_lo(pgdc), ptr);
 #else
-       UASM_i_LA_mostly(p, ptr, pgdc);
-       uasm_i_ld(p, ptr, uasm_rel_lo(pgdc), ptr);
-#endif
+               UASM_i_LA_mostly(p, ptr, pgdc);
+               uasm_i_ld(p, ptr, uasm_rel_lo(pgdc), ptr);
+#endif /* SMP */
+#endif  /* CONFIG_MIPS_PGD_C0_CONTEXT */
+       }
 
        uasm_l_vmalloc_done(l, *p);
 
@@ -939,31 +941,37 @@ build_get_pgd_vmalloc64(u32 **p, struct uasm_label **l, 
struct uasm_reloc **r,
 static void __cpuinit __maybe_unused
 build_get_pgde32(u32 **p, unsigned int tmp, unsigned int ptr)
 {
-       long pgdc = (long)pgd_current;
+       if (pgd_reg != -1) {
+               /* pgd is in pgd_reg */
+               uasm_i_mfc0(p, ptr, c0_kscratch, pgd_reg);
+               uasm_i_mfc0(p, tmp, C0_BADVADDR); /* get faulting address */
+       } else {
+               long pgdc = (long)pgd_current;
 
-       /* 32 bit SMP has smp_processor_id() stored in CONTEXT. */
+               /* 32 bit SMP has smp_processor_id() stored in CONTEXT. */
 #ifdef CONFIG_SMP
 #ifdef  CONFIG_MIPS_MT_SMTC
-       /*
-        * SMTC uses TCBind value as "CPU" index
-        */
-       uasm_i_mfc0(p, ptr, C0_TCBIND);
-       UASM_i_LA_mostly(p, tmp, pgdc);
-       uasm_i_srl(p, ptr, ptr, 19);
+               /*
+                * SMTC uses TCBind value as "CPU" index
+                */
+               uasm_i_mfc0(p, ptr, C0_TCBIND);
+               UASM_i_LA_mostly(p, tmp, pgdc);
+               uasm_i_srl(p, ptr, ptr, 19);
 #else
-       /*
-        * smp_processor_id() << 3 is stored in CONTEXT.
-         */
-       uasm_i_mfc0(p, ptr, C0_CONTEXT);
-       UASM_i_LA_mostly(p, tmp, pgdc);
-       uasm_i_srl(p, ptr, ptr, 23);
+               /*
+                * smp_processor_id() << 3 is stored in CONTEXT.
+                */
+               uasm_i_mfc0(p, ptr, C0_CONTEXT);
+               UASM_i_LA_mostly(p, tmp, pgdc);
+               uasm_i_srl(p, ptr, ptr, 23);
 #endif
-       uasm_i_addu(p, ptr, tmp, ptr);
+               uasm_i_addu(p, ptr, tmp, ptr);
 #else
-       UASM_i_LA_mostly(p, ptr, pgdc);
+               UASM_i_LA_mostly(p, ptr, pgdc);
 #endif
-       uasm_i_mfc0(p, tmp, C0_BADVADDR); /* get faulting address */
-       uasm_i_lw(p, ptr, uasm_rel_lo(pgdc), ptr);
+               uasm_i_mfc0(p, tmp, C0_BADVADDR); /* get faulting address */
+               uasm_i_lw(p, ptr, uasm_rel_lo(pgdc), ptr);
+       }
        uasm_i_srl(p, tmp, tmp, PGDIR_SHIFT); /* get pgd only bits */
        uasm_i_sll(p, tmp, tmp, PGD_T_LOG2);
        uasm_i_addu(p, ptr, ptr, tmp); /* add in pgd offset */
@@ -1446,16 +1454,17 @@ static void __cpuinit 
build_r4000_tlb_refill_handler(void)
 u32 handle_tlbl[FASTPATH_SIZE] __cacheline_aligned;
 u32 handle_tlbs[FASTPATH_SIZE] __cacheline_aligned;
 u32 handle_tlbm[FASTPATH_SIZE] __cacheline_aligned;
-#ifdef CONFIG_MIPS_PGD_C0_CONTEXT
 u32 tlbmiss_handler_setup_pgd[16] __cacheline_aligned;
 
-static void __cpuinit build_r4000_setup_pgd(void)
+static void __cpuinit build_setup_pgd(void)
 {
        const int a0 = 4;
-       const int a1 = 5;
+       const int __maybe_unused a1 = 5;
+       const int a2 = 6;
        u32 *p = tlbmiss_handler_setup_pgd;
-       struct uasm_label *l = labels;
-       struct uasm_reloc *r = relocs;
+#ifndef CONFIG_MIPS_PGD_C0_CONTEXT
+       long pgdc = (long)pgd_current;
+#endif
 
        memset(tlbmiss_handler_setup_pgd, 0, sizeof(tlbmiss_handler_setup_pgd));
        memset(labels, 0, sizeof(labels));
@@ -1463,7 +1472,11 @@ static void __cpuinit build_r4000_setup_pgd(void)
 
        pgd_reg = allocate_kscratch();
 
+#ifdef CONFIG_MIPS_PGD_C0_CONTEXT
        if (pgd_reg == -1) {
+               struct uasm_label *l = labels;
+               struct uasm_reloc *r = relocs;
+
                /* PGD << 11 in c0_Context */
                /*
                 * If it is a ckseg0 address, convert to a physical
@@ -1485,6 +1498,36 @@ static void __cpuinit build_r4000_setup_pgd(void)
                uasm_i_jr(&p, 31);
                UASM_i_MTC0(&p, a0, c0_kscratch, pgd_reg);
        }
+#else
+#if defined(CONFIG_SMP)
+# ifdef CONFIG_MIPS_MT_SMTC
+       /*
+        * SMTC uses TCBind value as "CPU" index
+        */
+       uasm_i_mfc0(&p, a1, C0_TCBIND);
+       uasm_i_dsrl_safe(&p, a1, a1, 19);
+# else
+       /*
+        * 64 bit SMP running in XKPHYS has smp_processor_id() << 3
+        * stored in CONTEXT.
+        */
+       UASM_i_MFC0(&p, a1, C0_CONTEXT);
+       uasm_i_dsrl_safe(&p, a1, a1, 23);
+# endif
+       UASM_i_LA_mostly(&p, a2, pgdc);
+       UASM_i_ADDU(&p, a2, a2, a1);
+       UASM_i_SW(&p, a0, uasm_rel_lo(pgdc), a2);
+#else
+       UASM_i_LA_mostly(&p, a2, pgdc);
+       UASM_i_SW(&p, a0, uasm_rel_lo(pgdc), a2);
+#endif /* SMP */
+       uasm_i_jr(&p, 31);
+       if (pgd_reg != -1) {
+               /* PGD also in c0_KScratch */
+               UASM_i_MTC0(&p, a0, c0_kscratch, pgd_reg);
+       } else
+               uasm_i_nop(&p);
+#endif
        if (p - tlbmiss_handler_setup_pgd > 
ARRAY_SIZE(tlbmiss_handler_setup_pgd))
                panic("tlbmiss_handler_setup_pgd space exceeded");
        uasm_resolve_relocs(relocs, labels);
@@ -1494,7 +1537,6 @@ static void __cpuinit build_r4000_setup_pgd(void)
        dump_handler(tlbmiss_handler_setup_pgd,
                     ARRAY_SIZE(tlbmiss_handler_setup_pgd));
 }
-#endif
 
 static void __cpuinit
 iPTE_LW(u32 **p, unsigned int pte, unsigned int ptr)
@@ -2150,6 +2192,7 @@ void __cpuinit build_tlb_refill_handler(void)
 #ifndef CONFIG_MIPS_PGD_C0_CONTEXT
                build_r3000_tlb_refill_handler();
                if (!run_once) {
+                       build_setup_pgd();
                        build_r3000_tlb_load_handler();
                        build_r3000_tlb_store_handler();
                        build_r3000_tlb_modify_handler();
@@ -2173,9 +2216,7 @@ void __cpuinit build_tlb_refill_handler(void)
                if (!run_once) {
                        c0_kscratch = kscratch_reg();
                        scratch_reg = allocate_kscratch();
-#ifdef CONFIG_MIPS_PGD_C0_CONTEXT
-                       build_r4000_setup_pgd();
-#endif
+                       build_setup_pgd();
                        build_r4000_tlb_load_handler();
                        build_r4000_tlb_store_handler();
                        build_r4000_tlb_modify_handler();
@@ -2193,8 +2234,6 @@ void __cpuinit flush_tlb_handlers(void)
                           (unsigned long)handle_tlbs + sizeof(handle_tlbs));
        local_flush_icache_range((unsigned long)handle_tlbm,
                           (unsigned long)handle_tlbm + sizeof(handle_tlbm));
-#ifdef CONFIG_MIPS_PGD_C0_CONTEXT
        local_flush_icache_range((unsigned long)tlbmiss_handler_setup_pgd,
                           (unsigned long)tlbmiss_handler_setup_pgd + 
sizeof(handle_tlbm));
-#endif
 }
-- 
1.7.9.5



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