From 4badd43ae44109c88438cc6421d208f513cf537f Mon Sep 17 00:00:00 2001 From: Christophe Leroy Date: Tue, 17 May 2016 09:02:45 +0200 Subject: [PATCH] powerpc/8xx: Map IMMR area with 512k page at a fixed address Once the linear memory space has been mapped with 8Mb pages, as seen in the related commit, we get 11 millions DTLB missed during the reference 600s period. 77% of the misses are on user addresses and 23% are on kernel addresses (1 fourth for linear address space and 3 fourth for virtual address space) Traditionaly, each driver manages one computer board which has its own components with its own memory maps. But on embedded chips like the MPC8xx, the SOC has all registers located in the same IO area. When looking at ioremaps done during startup, we see that many drivers are re-mapping small parts of the IMMR for their own use and all those small pieces gets their own 4k page, amplifying the number of TLB misses: in our system we get 0xff000000 mapped 31 times and 0xff003000 mapped 9 times. Even if each part of IMMR was mapped only once with 4k pages, it would still be several small mappings towards linear area. This patch maps the IMMR with a single 512k page. With this patch applied, the number of DTLB misses during the 10 min period is reduced to 11.8 millions for a duration of 5.8s, which represents 2% of the non-idle time hence yet another 10% reduction. Signed-off-by: Christophe Leroy Signed-off-by: Scott Wood --- arch/powerpc/kernel/head_8xx.S | 29 ++++++++++++++++++++++ arch/powerpc/mm/8xx_mmu.c | 56 +++++++++++++++++++++++++++++++++++++++++- arch/powerpc/mm/mmu_decl.h | 3 ++- 3 files changed, 86 insertions(+), 2 deletions(-) diff --git a/arch/powerpc/kernel/head_8xx.S b/arch/powerpc/kernel/head_8xx.S index 378a185..44f4edb 100644 --- a/arch/powerpc/kernel/head_8xx.S +++ b/arch/powerpc/kernel/head_8xx.S @@ -384,6 +384,27 @@ InstructionTLBMiss: EXCEPTION_EPILOG_0 rfi +/* + * Bottom part of DataStoreTLBMiss handler for IMMR area + * not enough space in the DataStoreTLBMiss area + */ +DTLBMissIMMR: + mtcr r3 + /* Set 512k byte guarded page and mark it valid */ + li r10, MD_PS512K | MD_GUARDED | MD_SVALID + MTSPR_CPU6(SPRN_MD_TWC, r10, r3) + mfspr r10, SPRN_IMMR /* Get current IMMR */ + rlwinm r10, r10, 0, 0xfff80000 /* Get 512 kbytes boundary */ + ori r10, r10, 0xf0 | MD_SPS16K | _PAGE_SHARED | _PAGE_DIRTY | \ + _PAGE_PRESENT | _PAGE_NO_CACHE + MTSPR_CPU6(SPRN_MD_RPN, r10, r3) /* Update TLB entry */ + + li r11, RPN_PATTERN + mfspr r3, SPRN_SPRG_SCRATCH2 + mtspr SPRN_DAR, r11 /* Tag DAR */ + EXCEPTION_EPILOG_0 + rfi + . = 0x1200 DataStoreTLBMiss: mtspr SPRN_SPRG_SCRATCH2, r3 @@ -397,6 +418,14 @@ DataStoreTLBMiss: IS_KERNEL(r11, r10) mfspr r11, SPRN_M_TW /* Get level 1 table */ BRANCH_UNLESS_KERNEL(3f) + + rlwinm r11, r10, 16, 0xfff8 +#ifndef CONFIG_PIN_TLB + cmpli cr0, r11, VIRT_IMMR_BASE@h +_ENTRY(DTLBMiss_jmp) + beq- DTLBMissIMMR +#endif + lis r11, (swapper_pg_dir-PAGE_OFFSET)@ha 3: diff --git a/arch/powerpc/mm/8xx_mmu.c b/arch/powerpc/mm/8xx_mmu.c index 9491005..2207725 100644 --- a/arch/powerpc/mm/8xx_mmu.c +++ b/arch/powerpc/mm/8xx_mmu.c @@ -13,10 +13,43 @@ */ #include +#include +#include #include "mmu_decl.h" +#define IMMR_SIZE (FIX_IMMR_SIZE << PAGE_SHIFT) + extern int __map_without_ltlbs; + +/* + * Return PA for this VA if it is in IMMR area, or 0 + */ +phys_addr_t v_block_mapped(unsigned long va) +{ + unsigned long p = PHYS_IMMR_BASE; + + if (__map_without_ltlbs) + return 0; + if (va >= VIRT_IMMR_BASE && va < VIRT_IMMR_BASE + IMMR_SIZE) + return p + va - VIRT_IMMR_BASE; + return 0; +} + +/* + * Return VA for a given PA or 0 if not mapped + */ +unsigned long p_block_mapped(phys_addr_t pa) +{ + unsigned long p = PHYS_IMMR_BASE; + + if (__map_without_ltlbs) + return 0; + if (pa >= p && pa < p + IMMR_SIZE) + return VIRT_IMMR_BASE + pa - p; + return 0; +} + /* * MMU_init_hw does the chip-specific initialization of the MMU hardware. */ @@ -29,6 +62,22 @@ void __init MMU_init_hw(void) #define LARGE_PAGE_SIZE_8M (1<<23) #define LARGE_PAGE_SIZE_64M (1<<26) +static void mmu_mapin_immr(void) +{ + unsigned long p = PHYS_IMMR_BASE; + unsigned long v = VIRT_IMMR_BASE; + unsigned long f = pgprot_val(PAGE_KERNEL_NCG); + int offset; + + for (offset = 0; offset < IMMR_SIZE; offset += PAGE_SIZE) + map_page(v + offset, p + offset, f); +} + +/* Address of instructions to patch */ +#ifndef CONFIG_PIN_TLB +extern unsigned int DTLBMiss_jmp; +#endif + unsigned long __init mmu_mapin_ram(unsigned long top) { unsigned long v, s, mapped; @@ -38,8 +87,13 @@ unsigned long __init mmu_mapin_ram(unsigned long top) p = 0; s = top; - if (__map_without_ltlbs) + if (__map_without_ltlbs) { + mmu_mapin_immr(); +#ifndef CONFIG_PIN_TLB + patch_instruction(&DTLBMiss_jmp, PPC_INST_NOP); +#endif return 0; + } #ifdef CONFIG_PPC_4K_PAGES while (s >= LARGE_PAGE_SIZE_8M) { diff --git a/arch/powerpc/mm/mmu_decl.h b/arch/powerpc/mm/mmu_decl.h index 6af6532..f988db6 100644 --- a/arch/powerpc/mm/mmu_decl.h +++ b/arch/powerpc/mm/mmu_decl.h @@ -154,9 +154,10 @@ struct tlbcam { }; #endif -#if defined(CONFIG_6xx) || defined(CONFIG_FSL_BOOKE) +#if defined(CONFIG_6xx) || defined(CONFIG_FSL_BOOKE) || defined(CONFIG_PPC_8xx) /* 6xx have BATS */ /* FSL_BOOKE have TLBCAM */ +/* 8xx have LTLB */ phys_addr_t v_block_mapped(unsigned long va); unsigned long p_block_mapped(phys_addr_t pa); #else -- 2.7.4