Commit 4badd43a authored by Christophe Leroy's avatar Christophe Leroy Committed by Scott Wood
Browse files

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: default avatarChristophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: default avatarScott Wood <oss@buserror.net>
parent f86ef74e

arch/powerpc/kernel/head_8xx.S

+29 −0
Original line number Diff line number Diff line
@@ -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:

arch/powerpc/mm/8xx_mmu.c

+55 −1
Original line number Diff line number Diff line
@@ -13,10 +13,43 @@ 
 */



#include <linux/memblock.h>

#include <asm/fixmap.h>

#include <asm/code-patching.h>



#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) {

arch/powerpc/mm/mmu_decl.h

+2 −1
Original line number Diff line number Diff line
@@ -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

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